WARNING:http_to_spdy_filter.cc(113) HttpToSpdyFilter is not the last filter in the chain: http_to_spdy

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Several folks have reported seeing this warning in their Apache logs:

  [9179:9180:WARNING:http_to_spdy_filter.cc(113)] HttpToSpdyFilter is not the last filter in the chain: http_to_spdy

The "HttpToSpdyFilter is not the last filter in the chain" warning is issued
when there is an output filter later in the chain that the HTTP-to-SPDY 
translation filter, which normally shouldn't happen.  Even stranger, the above 
warning indicates that the filter that comes later in the chain is the 
HTTP-to-SPDY filter itself.  I am not sure yet how that is happening.

Original issue reported on code.google.com by mdste...@google.com on 19 Apr 2012 at 9:16

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Posting output of apache2ctl -M as requested on discussion list:

 core_module (static)
 log_config_module (static)
 logio_module (static)
 mpm_prefork_module (static)
 http_module (static)
 so_module (static)
 auth_pgsql_module (shared)
 alias_module (shared)
 auth_basic_module (shared)
 authn_dbd_module (shared)
 authn_file_module (shared)
 authz_default_module (shared)
 authz_groupfile_module (shared)
 authz_host_module (shared)
 authz_user_module (shared)
 autoindex_module (shared)
 cgi_module (shared)
 deflate_module (shared)
 dir_module (shared)
 env_module (shared)
 expires_module (shared)
 headers_module (shared)
 include_module (shared)
 mime_module (shared)
 negotiation_module (shared)
 php5_module (shared)
 proxy_module (shared)
 proxy_http_module (shared)
 python_module (shared)
 reqtimeout_module (shared)
 rewrite_module (shared)
 setenvif_module (shared)
 spdy_module (shared)
 ssl_module (shared)
 status_module (shared)

[I ended up disabling mod_spdy due to issues with my php install]

Original comment by vanch...@gmail.com on 28 Apr 2012 at 10:09

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I note that you seem to be using mod_php with mod_spdy, which can cause 
problems due to PHP's lack of thread safety (the same problem comes up when 
using mod_php with Apache Worker rather than Apache Prefork).

See here for some information on how to configure Apache to use PHP safely with 
mod_spdy: https://developers.google.com/speed/spdy/mod_spdy/php

Original comment by mdste...@google.com on 2 May 2012 at 8:13

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I have same warning combining mod_fcgi and apache-worker-mpm. 
This doesn't occur with prefork and fcgi. 
Is worker-mpm not supported by mod_spdy?
Couldn't find anything about the worker-mpm support in the docs.
(Just the fact, that it is a similar thread model to mod_spdy)

Original comment by in.gottw...@gmail.com on 4 May 2012 at 7:19

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Hmm, that is very interesting to know, thank you.  In general, mod_spdy should 
definitely be compatible with worker-mpm (in fact, most of the mod_spdy testing 
I do is on worker).  Strange that the warning shows up for you with worker but 
not prefork.

Other than getting this warning, does everything else work fine when you use 
mod_spdy with fcgid/worker, or are you seeing any other misbehavior?

I _think_ this warning should be harmless (other than filling up the logs, 
which is obviously an issue), but despite my efforts I have yet to be able to 
reproduce it locally, even though I know a number of folks are seeing it.  I'll 
keep working on it.

Original comment by mdste...@google.com on 4 May 2012 at 2:43

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I believe this should be fixed in trunk as of r323.

Original comment by mdste...@google.com on 15 May 2012 at 2:09

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Original comment by mdste...@google.com on 15 May 2012 at 2:09

• Changed state: Fixed