# Problem with post\_action when used with return 202; and POST request **URL:** \ **Category:** NGINX\ **Created:** [August 10, 2011, 1:23pm UTC](https://www.ruby-forum.com/t/problem-with-post-action-when-used-with-return-202-and-post-request/210530 "2011-08-10T13:23:13Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\ **Post date:** [August 10, 2011, 1:23pm UTC](https://www.ruby-forum.com/t/problem-with-post-action-when-used-with-return-202-and-post-request/210530/1 "2011-08-10T13:23:13Z")
Hi, We are trying to use post\_action in a location block that only has “return 202;”. Everything works fine for GET requests and with small POST requests, but if the client request body + headers are over 1kB, nginx will not trigger the post\_action handler. Test configuration, and debug log attached. Following commands can be used to trigger the error: dd if=/dev/zero of=request\_body count=2 wget -d --post-file=request\_body localhost:8022 Is this a bug or just the way it should work? I tested it with nginx 1.0.5 and 1.1.0, both appear to be working the same way. I worked around it by creating a small module that just calls ngx\_http\_read\_client\_request\_body() and returns 202 from the callback. But I feel that it might not be the right solution for this. (module also attached) Also while debugging I found another possibly related bug, if you do a POST request against location / { return 202; } block, it will incorrectly result in 2 lines in access log: 127.0.0.1 - - [10/Aug/2011:14:07:40 +0300] “POST / HTTP/1.1” 202 0 “-” “curl/7.21.0 (x86\_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o zlib/1.2.3.4 libidn/1.18” 127.0.0.1 - - [10/Aug/2011:14:07:40 +0300] “foobar=foo” 400 172 “-” “-” Happy to provide more information if needed. Thanks, Pyry ---
**Author:** ![Pyry\_Hakulinen](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ecd19e/32.png) [@Pyry\_Hakulinen](https://www.ruby-forum.com/u/Pyry_Hakulinen)\ **Post date:** [August 11, 2011, 1:39pm UTC](https://www.ruby-forum.com/t/problem-with-post-action-when-used-with-return-202-and-post-request/210530/2 "2011-08-11T13:39:34Z")
> Thank you for your report.  Please try the attached patch. Thank you, the patch appears to be working fine, but because it discards the request body, it isn’t going to work for our use case. Our use case is, to POST data to nginx and let nginx asynchronously proxy it to somewhere else for processing, while freeing the client that did the POSTing to do other things. I think the request body should be transferred to post\_action location, and the location can then decide if it needs it or not. Attached is a patch against 1.0.5 that reads the body if post\_action is used, but I’m not really sure if it’s correct. My nginx-fu is still a bit lacking. Thanks, Pyry ---
**Author:** ![Pyry\_Hakulinen](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ecd19e/32.png) [@Pyry\_Hakulinen](https://www.ruby-forum.com/u/Pyry_Hakulinen)\ **Post date:** [August 11, 2011, 1:10am UTC](https://www.ruby-forum.com/t/problem-with-post-action-when-used-with-return-202-and-post-request/210530/3 "2011-08-11T01:10:41Z")
Hello! On Wed, Aug 10, 2011 at 02:18:41PM +0300, Pyry Hakulinen wrote: > dd if=/dev/zero of=request\_body count=2 > Also while debugging I found another possibly related bug, if you do a > POST request against location / { return 202; } block, it will > incorrectly result in 2 lines in access log: > > 127.0.0.1 - - [10/Aug/2011:14:07:40 +0300] “POST / HTTP/1.1” 202 0 “-” > “curl/7.21.0 (x86\_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o > zlib/1.2.3.4 libidn/1.18” > 127.0.0.1 - - [10/Aug/2011:14:07:40 +0300] “foobar=foo” 400 172 “-” “-” > > Happy to provide more information if needed. Thanks, > Pyry Thank you for your report. Please try the attached patch. Maxim D. ---
**Author:** ![Pyry\_Hakulinen](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ecd19e/32.png) [@Pyry\_Hakulinen](https://www.ruby-forum.com/u/Pyry_Hakulinen)\ **Post date:** [August 12, 2011, 9:46am UTC](https://www.ruby-forum.com/t/problem-with-post-action-when-used-with-return-202-and-post-request/210530/4 "2011-08-12T09:46:52Z")
Hello! On Thu, Aug 11, 2011 at 02:38:44PM +0300, Pyry Hakulinen wrote: > location, and the location can then decide if it needs it or not. > Attached is a patch against 1.0.5 that reads the body if post\_action > is used, but I’m not really sure if it’s correct. My nginx-fu is still > a bit lacking. No, this is incorrect. Body should be either read or discarded before response could be returned (else communication with clients which write body and only then read response will just deadlock). And it’s up to code returning response to decide whether it needs body or not, post\_action has nothing to do with it. (I personally consider post\_action to be a dirty hack which should be removed entirely, and it’s not officially documented on purpose, but that’s another story.) In you particular case I would recommend actually using module to read body and return 202 response instead of using “return 202”. Maxim D. ---
**Author:** ![Pyry\_Hakulinen](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ecd19e/32.png) [@Pyry\_Hakulinen](https://www.ruby-forum.com/u/Pyry_Hakulinen)\ **Post date:** [August 13, 2011, 10:07pm UTC](https://www.ruby-forum.com/t/problem-with-post-action-when-used-with-return-202-and-post-request/210530/5 "2011-08-13T22:07:09Z")
Howdy, > No, this is incorrect. Body should be either read or discarded > before response could be returned (else communication with clients > which write body and only then read response will just deadlock). Ah, indeed, I see what you mean. I didn’t see it deadlock, but I really didn’t test it all that much. Thanks for looking. > (I personally consider post\_action to be a dirty hack which should > be removed entirely, and it’s not officially documented on purpose, > but that’s another story.) Yeah, it looks like it isn’t that reliable when used with POST requests. For example, using this: ``` location / { proxy_pass http://some.server; post_action @post; } location @post { proxy_pass http://some.server; } ``` post\_action will fail when client request body is buffered to a temp file. Can be “fixed” by increasing client\_body\_buffer\_size or by discarding request body in @post location (proxy\_pass\_request\_body off; proxy\_set\_header Content-Length 0;). > In you particular case I would recommend actually using module to > read body and return 202 response instead of using “return 202”. Thanks, this is probably what we will end up doing. -Pyry