zlib(finalizer): the stream was freed prematurely. when using compression

[mfazekas]

require 'sshkit'
require 'sshkit/dsl'

SSHKit::Backend::Netssh.config.ssh_options = {compression: true, compression_level: 9}

on 'localhost' do
  ls_output = capture(:ls, '-l')
end

It outputs:

...
zlib(finalizer): the stream was freed prematurely.

the issue is that sshkit doesn't close the net-ssh connection which then cannot close the zlib stream which has finalizer and complains.

as a workaround

SSHKit::Backend::Netssh.pool.close_connections

can be added thanks to #285
see also net-ssh/net-ssh#284

[leehambley]

Maybe this issue should be on Capistrano, that we should setup something to call this before the programme exists, we need the pool to keep connections as long as possible.

[mfazekas]

Agree on capistrano, i think what sshkit can do is to have a nicer method to close esp in 'dsl', and promote it's use through examples.

[mattbrictson]

Would this work instead?

--- a/lib/sshkit/backends/connection_pool.rb
+++ b/lib/sshkit/backends/connection_pool.rb
@@ -47,6 +47,7 @@ class SSHKit::Backend::ConnectionPool
     @caches.extend(MonitorMixin)
     @timed_out_connections = Queue.new
     Thread.new { run_eviction_loop }
+    at_exit { close_connections }
   end

[mfazekas]

That should work as well. One corner case is if there is a connection issue, and server not responding user press ctrl+C to abort the program, in this case we might not want to cleanly close the connections as that could be facing the connection issue again. So you might want to do this:

   at_exit { close_connections unless $! }