Error with TLS and require_ack_response

[mpeltonen]

Trying to setup (fluentd 14.14) out_forward plugin with TLS and at-least-once semantics. When I set require_ack_response true, I get this:

2017-04-27 14:51:15 +0300 [error]: #0 [aggregator_output] unexpected error while receiving ack message error_class=NoMethodError error="undefined method 'recv' for #<Fluent::PluginHelper::Socket::WrappedSocket::TLS:0x007f6849b06108>"
2017-04-27 14:51:15 +0300 [error]: #0 /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.14.14/lib/fluent/plugin/out_forward.rb:426:in 'read_ack_from_sock'
2017-04-27 14:51:15 +0300 [error]: #0 /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.14.14/lib/fluent/plugin/out_forward.rb:498:in 'block in ack_reader'
2017-04-27 14:51:15 +0300 [error]: #0 /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.14.14/lib/fluent/plugin/out_forward.rb:497:in 'each'
2017-04-27 14:51:15 +0300 [error]: #0 /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.14.14/lib/fluent/plugin/out_forward.rb:497:in 'ack_reader'
2017-04-27 14:51:15 +0300 [error]: #0 /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.14.14/lib/fluent/plugin_helper/thread.rb:78:in 'block in thread_create'

It looks like the reason is that Ruby's SSLSocket interface is different from TCPSocket (See for example https://bugs.ruby-lang.org/issues/12077 and https://bugs.ruby-lang.org/issues/8126).

There is probably a better way to fix this, but this seems to fix the issue for my case at least:

diff --git a/lib/fluent/plugin/out_forward.rb b/lib/fluent/plugin/out_forward.rb
index fb9d642..2eaf4c4 100644
--- a/lib/fluent/plugin/out_forward.rb
+++ b/lib/fluent/plugin/out_forward.rb
@@ -420,7 +420,7 @@ module Fluent::Plugin
     # return chunk id to be committed
     def read_ack_from_sock(sock, unpacker)
       begin
-        raw_data = sock.recv(@read_length)
+        raw_data = sock.instance_of? Fluent::PluginHelper::Socket::WrappedSocket::TLS ? sock.read(@read_length) : sock.recv(@read_length)
       rescue Errno::ECONNRESET
         raw_data = ""
       end

[repeatedly]

@nurse How about this? Do we need to consider more points?

[nurse]

@repeatedly This code doesn't use socket specific options for recv. Therefore just raw_data = sock.read(@read_length) is also ok. (FIXED TYPO)

[mpeltonen]

Therefore just raw_data = sock.recv(@read_length) is also ok.

Hmm, what do you mean by that? 'recv' is the method that is missing from SSLSocket and what causes the error with TLS transport?

[nurse]

@mpeltonen Oops sorry, it is typo. It must be raw_data = sock.read(@read_length)

[mpeltonen]

Ah, right! I was also thinking that maybe just recv -> read would work, but was not sure about the semantics.

Would appreciate 0.14.16 soon with this change :)

[repeatedly]

We will merge the patch soon: #1560