25 Jan
2024
25 Jan
'24
11:19 p.m.
Issue #20215 has been reported by ioquatix (Samuel Williams).
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
1 Feb
1 Feb
12:19 a.m.
New subject: [ruby-core:116546] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by shyouhei (Shyouhei Urabe).
After thinking it for a while, yes I'm for this feature. There seems to be no way
right now to achieve what is needed.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-106563
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
8:59 a.m.
New subject: [ruby-core:116547] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by Dan0042 (Daniel DeLorme).
I'm interested in this. I previously had to implement a "nonblocking gets"
which was a bit tricky.
```ruby
def gets_nonblock(io)
str = io.read_nonblock(1, exception: false)
return :no_data if str == :wait_readable
if str == $/
enc = $/.encoding
else
str2 = io.gets.to_s
enc = str2.encoding
str << str2.force_encoding(Encoding::ASCII_8BIT)
end
str.force_encoding(enc)
rescue EOFError
nil
end
```
It would have been nice to just write `io.gets if io.readable?`
But I want to confirm this is the expected behavior: `#readable?` should return true if
there is data immediately available for `#read`
Based on the BasicSocket implementation above, it seems like `#readable?` could return
true even if no data is available?
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-106564
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
2 Feb
2 Feb
3:06 p.m.
New subject: [ruby-core:116561] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by Eregon (Benoit Daloze).
Would `io.wait_readable(0)` work instead? If not, why not?
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-106578
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
3 Feb
3 Feb
11:13 a.m.
New subject: [ruby-core:116566] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by Dan0042 (Daniel DeLorme).
Interesting, I didn't know about #wait_readable. Looks like previously it needed
`require "io/wait"` but it was integrated in Ruby 3.2 core.
Unfortunately it doesn't work for my use case:
```
(echo 1;sleep 1;echo 2)|3.2 ruby -e '8.times{p(gets:$stdin.gets,
closed:$stdin.closed?) if p $stdin.wait_readable(0); sleep 0.2}'
#<IO:<STDIN>>
{:gets=>"1\n", :closed=>false}
nil
nil
nil
nil
#<IO:<STDIN>>
{:gets=>"2\n", :closed=>false}
#<IO:<STDIN>>
{:gets=>nil, :closed=>false}
#<IO:<STDIN>>
{:gets=>nil, :closed=>false}
```
If #wait_readable returns `#<IO:<STDIN>>`, the subsequent #gets should never
return nil.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-106582
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
1:53 p.m.
New subject: [ruby-core:116567] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by Dan0042 (Daniel DeLorme).
Actually if I think about it a little, I can work around that like this:
```ruby
loop do
if $stdin.wait_readable(0)
str = $stdin.gets or abort("<eof>")
p str
else
puts "no input, let's wait a bit..."
sleep 1
end
end
```
And I now realize this is the same as `IO.select`; not sure why I didn't think of
using that before.
Which brings me to understand what @ioquatix has in mind is a bit different from what I
thought. It looks like it can be implemented like this?
```ruby
class IO
def readable?
if IO.select([self],[],[],0).nil?
true #no data available but not eof
else
!eof? #will not hang due to check above
end
end
#or, what about adding an argument to eof?
def eof?(non_blocking=false)
if non_blocking
return nil if IO.select([self],[],[],0).nil?
end
super
end
end
```
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-106583
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
19 Feb
19 Feb
12:44 p.m.
New subject: [ruby-core:116851] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by forthoney (Seong-Heon Jung).
I think the name is potentially confusing. Consider the following:
```ruby
if client.readable?
client.read # this may block
end
```
I personally would be a bit surprised if `client.read` blocked despite `client.readable?`
returning true. `readable` is ambiguous between "there is something to read right
now" and "there will eventually be something to read".
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-106883
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
15 Apr
15 Apr
8:13 p.m.
New subject: [ruby-core:117521] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by ioquatix (Samuel Williams).
Would io.wait_readable(0) work instead? If not, why
not?
(1) I don't think it makes sense to add `wait_*` to `StringIO` but it does make sense
to add `readable?` to `StringIO`.
(2) `wait_readable(0)` is impossible to replicate the desired behaviour:
```
r, w = Socket.pair(:UNIX, :STREAM)
=>
[#<Socket:fd 5>, #<Socket:fd 6>]
irb(main):003> r.wait_readable(0)
=> nil # Not readable (no data available right now within the timeout specified)
irb(main):004> r.readable?
=> true # It's possible to read from this socket.
irb(main):005> w.close
=> nil
irb(main):006> r.wait_readable(0)
=> #<Socket:fd 5> # It's possible to read the "close" (zero-size).
irb(main):007> r.readable?
=> false # The socket is not readable (call to `#read` will not give data).
```
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-107910
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
16 Apr
16 Apr
4:54 a.m.
New subject: [ruby-core:117528] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by ioquatix (Samuel Williams).
After some discussion, I investigated libc's `feof`:
1.
https://github.com/bminor/glibc/blob/14e56bd4ce15ac2d1cc43f762eb2e6b83fec1a…
2.
https://github.com/bminor/glibc/blob/14e56bd4ce15ac2d1cc43f762eb2e6b83fec1a…
It looks like the expected behaviour of "eof?" should be non-blocking.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-107918
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
12:36 p.m.
New subject: [ruby-core:117537] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by mame (Yusuke Endoh).
Before the dev meeting, I talked with @akr, who designed the Ruby IO, but we could not
understand the motivation of the following branch.
```
if client.eof? # <--- Can hang here!
```
Can you explain what you want to do by this branch? Even if `client.eof?` returns false
without blocking, it could still result in an EOF with zero read bytes. Therefore, it
would be better to do read without unnecessary checks.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-107928
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
7:07 p.m.
New subject: [ruby-core:117541] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by ioquatix (Samuel Williams).
Even if client.eof? returns false without blocking, it
could still result in an EOF with zero read bytes. Therefore, it would be better to do
read without unnecessary checks.
I understand, thanks for your question. I may not be able to answer this well before the
meeting, so I'll try to come up with a clear justification, but if the time frame is
too tight, I'll discuss it next time instead.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-107933
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
8:13 p.m.
New subject: [ruby-core:117542] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by akr (Akira Tanaka).
I couldn't understand the motivation of this issue.
However, the state of the read side of unidirectional data flow (Unix pipe, half of a
stream socket, etc.) can be one of the following.
1. We can read 1 or more bytes immediately.
2. We can detect EOF immediately.
3. We cannot determine data/EOF immediately. If we wait indefinitely, we can read 1 or
more bytes.
4. We cannot determine data/EOF immediately. If we wait indefinitely, we can detect EOF.
`io.eof?` returns true on 2 and 4, false otherwise. (So, it blocks on 3 and 4.)
`io.wait_readable(0)` returns truthy on 1 and 2, falsy otherwise.
They are enough to distinguish the states.
If we don't want to block, it is impossible to distinguish 3 and 4, though.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-107934
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
11:25 p.m.
New subject: [ruby-core:117544] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by ioquatix (Samuel Williams).
After considering the various use cases I have, I think the easiest to describe problem is
knowing whether a connection is still "connected" or not, i.e. whether read will
definitely fail or might succeed.
I added a full working example of the problem here:
<https://github.com/socketry/protocol-http1/blob/540551bdbdbca06d746b4c4545af2d73ebcc7dcc/examples/http1/client.rb#L70>.
You can try different implementation of `IO#readable?` to see the behaviour.
The example demonstrates HTTP/1 persistent connection handling, where the remote server
may at any time disconnect. In `server.rb`, it has a 50% chance of disconnecting.
`client.rb` makes 10 connections, and tries to use persistent connections.
The key problem that I'm trying to address, is that there is no protocol-level
mechanism to advertise that the remote server is closing the connection (in contrast,
HTTP/2 has such a feature). So, what that means, is in the request loop, when we want to
write the request, we want to ensure, with the best effort possible, that the connection
is still alive and working. That is the purpose of `IO#readable?` in this context -
whether there is a significantly good chance that writing an HTTP request will be
successful.
In practice, persistent connections may sit in a connection pool for minutes or hours, and
thus when you come to write a request, there is no easy operation to check "Is this
connection still working?". That is the purpose of `IO#readable?`. Specifically,
before writing a request, we check if the connection is still readable.
The logic for "Is the connection still readable?" depends on the situation and
the underlying IO. As you know there are many different semantics for handling Sockets,
Pipes, and so on, and we even provide our own blended semantics in `StringIO`. I'd
like to introduce `IO#readable?`, `BasicSocket#readable?` based on `recv_nonblock` and
`StringIO#readable?` which is similar to non-blocking `eof?`.
In other words, in the case of sockets, `BasicSocket#readable?` is querying the operating
system to find out if the TCP connection is still working (i.e. not closed explicitly).
It's true that this can be a race condition, for example the TCP reset/shutdown could
be delayed or received while writing the request. However, it's still better to
prevent writing the request entirely if possible. That's because not all requests are
idempotent e.g. POST requests for handling payments. It's much better to know ahead of
time that the request will fail because the persistent connection has been shut down, than
to find out half way through writing the non-idempotent request.
Example output from the client:
```
bundle exec client.rb
Connected to
#<Socket:0x0000754fc63d8b60> #<Addrinfo: 127.0.0.1:8080 TCP>
Writing request...
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Client is not readable, closing...
Reconnecting...
Connected to #<Socket:0x0000754fc63d0fa0> #<Addrinfo: 127.0.0.1:8080 TCP>
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Client is not readable, closing...
Reconnecting...
Connected to #<Socket:0x0000754fc644d2d0> #<Addrinfo: 127.0.0.1:8080 TCP>
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Client is not readable, closing...
Reconnecting...
Connected to #<Socket:0x0000754fc6448cf8> #<Addrinfo: 127.0.0.1:8080 TCP>
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Client is not readable, closing...
Reconnecting...
Connected to #<Socket:0x0000754fc6443f00> #<Addrinfo: 127.0.0.1:8080 TCP>
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Client is not readable, closing...
Reconnecting...
Connected to #<Socket:0x0000754fc64bfe20> #<Addrinfo: 127.0.0.1:8080 TCP>
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Writing request...
Client is not readable, closing...
Reconnecting...
Connected to #<Socket:0x0000754fc64bc2e8> #<Addrinfo: 127.0.0.1:8080 TCP>
Reading response...
Got response: ["HTTP/1.1", 200, "OK", #<Protocol::HTTP::Headers
[["Content-Type", "text/plain"]]>,
#<Protocol::HTTP1::Body::Fixed length=11 remaining=11>]
Hello World
Closing client...
Exiting.
```
Note that `Client is not readable, closing...` indicates that the client was closed before
the request was written, which is the ideal case.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-107937
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
17 Apr
17 Apr
6:16 p.m.
New subject: [ruby-core:117580] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by akr (Akira Tanaka).
Thank you for the explanation of the motivation.
I feel it is reasonable.
However, mame-san still had a question yesterday: why don't you detect an error in
writing a request?
I guess it is because writing the request may not fail.
It needs two writes to detect the error.
(The first write in a client application causes the client kernel to send a packet to the
server.
The server kernel responds to it with a RST packet because the server socket is closed.
The client kernel receives the RST packet and detects we cannot send data in the
connection.
The second write in the client application will cause an error.)
Please point out if I am wrong.
My next question is why `io.eof?` and `io.wait_readable(0)` doesn't fulfill your
motivation.
My current guess is related to the buffering mechanism of IO class.
But I'm not certain.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-107980
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
18 Apr
18 Apr
8:20 p.m.
New subject: [ruby-core:117603] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by Dan0042 (Daniel DeLorme).
ioquatix (Samuel Williams) wrote in #note-13:
In practice, persistent connections may sit in a
connection pool for minutes or hours, and thus when you come to write a request, there is
no easy operation to check "Is this connection still working?". That is the
purpose of `IO#readable?`.
In other words, in the case of sockets, `BasicSocket#readable?` is querying the operating
system to find out if the TCP connection is still working (i.e. not closed explicitly).
That makes a lof of sense to me, from personal experience. But I implore you to reconsider
the naming `readable?`
Just like @forthoney, I personally would be quite surprised if `client.read` blocked
despite `client.readable?` returning true. If the purpose is to check that the connection
is still open, then maybe `#still_open?` would work as a name? Actually, given the
description above that mentions "if the TCP connection is still working",
I'm not quite sure why you say this method is like `eof?` rather than `closed?`
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-108012
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
21 Apr
21 Apr
11:06 p.m.
New subject: [ruby-core:117636] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by ioquatix (Samuel Williams).
Regarding naming, I had other ideas like `open?` or `connected?` but I think they have
their own issues. I think my preference is `readable?` but I'd like to hear
alternatives. Maybe `open?` is okay but it sounds like the opposite of `closed?` which
strictly speaking it isn't.
Regarding implementation, I spent several hours debugging usage of `eof?`. Because `eof?`
can mutate the underlying buffer, it's not concurrency safe either. This was the
source of an extremely hard to diagnose bug where blocking `read` and `eof?` occurred in
different fibers.. Maybe we should create a separate issue, to make `eof?` safer (i.e. [it
doesn't call `io_fillbuf`
internally](https://github.com/ruby/ruby/blob/d42a8d66024f0a86c5a162eeffff1…).
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-108044
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
11:08 p.m.
New subject: [ruby-core:117637] [Ruby master Feature#20215] Introduce `IO#readable?`
Issue #20215 has been updated by ioquatix (Samuel Williams).
I'm not quite sure why you say this method is like
eof? rather than closed?
We work with the interface and taxonomy given to us by POSIX.
`close(fd)` causes the file descriptor to become invalid.
It's different from what happens if the **remote end** closes or shuts down the
connection. In that case, the file descriptor is still valid, but operations like `read`
and `write` will fail.
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215#change-108045
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data
is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block
indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may
hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply
return false. The expectation is the user will subsequently call `read` which may then
wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still
be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data
avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true
immediately, similar to `eof?`. This is not shown in the above implementation as I'm
not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
17
days inactive
104
days old
16 comments
7 participants
participants (7)
-
akr (Akira Tanaka) -
Dan0042 (Daniel DeLorme)
-
Eregon (Benoit Daloze)
-
forthoney (Seong-Heon Jung)
-
ioquatix (Samuel Williams)
-
mame (Yusuke Endoh)
-
shyouhei (Shyouhei Urabe)