Hi, list!

I'm happy to announce the v0.29 release of the ngx_echo module:

http://github.com/agentzh/echo-nginx-module/tarball/v0.29

As mentioned in some other threads on the nginx mailing list, I've completed the big refactoring of the ngx_echo module's core in this version to reflect my latest understanding (hopefully being quite complete and correct already) of the nginx internals.

Now the implementation of echo_subrequest, echo_location, echo_sleep, and echo_read_request_body directives has been massively rewritten. I'm trying to set up a design pattern for nginx content handlers that require to do various kinds of non-blocking I/O during its lifetime (similar to upstream modules but for different tasks like subrequests and others).

For sequential subrequests issued by the echo module's content handler, we now use a totally different approach.

Instead of issuing subrequests directly in our post_subrequest callback (as fed into the ngx_http_subrequest call), we now postpone firing the subrequests in a custom write event handler which will be called automatically once the current subrequest in question gets completely finalized (that post_subrequest callback is called by ngx_http_finalize_request of the subrequest in question).

This works because the parent request will always be waken up once its subrequest completes. (This is done by ngx_http_finalize_request via posting the parent request into the "posted requests" queue and the posted requests will be always called at the end of the top-level read/write event handler, i.e., ngx_http_request_handler).

This solves a lot of issues like mangled r->main->count and the following alert message when nginx is configured with the --with-debug option, for instance,

2010/05/05 16:46:14 [alert] 23853#0: *1 http finalize non-active request: "/main?" ...

We'll apply this trick to the upcoming ngx_lua and ngx_srcache modules soon :)

I've Cc'd the nginx-devel mailing list because other nginx developers might find this useful.

P.S. See the ngx_echo module's wiki page for more information: http://wiki.nginx.org/NginxHttpEchoModule