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Re: upgrade to 1-9.15 caused block requests

Maxim Dounin
November 22, 2018 08:40AM
Hello!

On Thu, Nov 22, 2018 at 07:15:41AM -0500, Ortal wrote:

> This is a small example of my code, I changed the code and in the current
> version on post/put request trying to read the buffer and print it, on any
> other requests just send response (I tried to minimal it as much as I
> could)
> On the current flow when running a post request with 1MB data the
> ngx_http_read_client_request_body return NGX_AGAIN and not call the
> post_handler
> I am not getting the ngx_http_block_reading for the request but I still do
> not get the request buffer, and the post_handler is not called

In no particular order:

1. In ngx_v3io_test_req_handler() you call
ngx_v3io_test_send_response() directly if the method is not PUT or
POST, and return NGX_OK. And in ngx_v3io_test_send_response() you
call ngx_http_finalize_request(req, NGX_DONE). This will result
in wrong request reference count as the request will be finalized
twice - first with ngx_http_finalize_request(req, NGX_DONE), and
then with NGX_OK returned from the handler. This will basically
preclude your code from working in non-POST/PUT codepath.

2. You ignore return code from the ngx_http_send_header(). While
unlikely, this can cause problems if anything different from
NGX_OK is returned.

3. In ngx_v3io_http_test_handle_post_req(), you call
ngx_handle_read_event(). This is not something you should do
unless you understand why you are doing this - usually, this is
something you should call only in low-level event handling
functions, when you are reading from the socket yourself. Doing
this in your code is certainly not needed and can cause problems.

4. In ngx_v3io_http_test_read_client_request_body(), you decrement
r->main->count manually. This is not something you are expected
to do, and will result in non-working code.

5. The return code of ngx_http_read_client_request_body() is not
handled correct. You are expected to do something like this:

rc = ngx_http_read_client_request_body(r, ngx_http_upstream_init);

if (rc >= NGX_HTTP_SPECIAL_RESPONSE) {
return rc;
}

return NGX_DONE;

in the request content handler, see, for example, PUT handling in
the DAV module code, or the development guide here:

http://nginx.org/en/docs/dev/development_guide.html#http_request_body

Your code seems to return NGX_AGAIN in most common cases of NGX_OK
and NGX_AGAIN instead, and this will lead to undefined results.
And this is what causes your immediate problems as seen in the
debug logs.

6. After reading the request body, you finalize the request in
ngx_v3io_test_send_response() with NGX_DONE. This is incorrect,
as due to NGX_DONE nginx will assume that something else is going
to happen on the request. Instead, you should use the code
returned by ngx_http_send_header().

Overall, it looks like there are too many problems in the module
to work. It may be a good idea to re-write it from scratch,
using an nginx module as an example (and looking into the
development guide).

--
Maxim Dounin
http://mdounin.ru/
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Subject Author Posted

upgrade to 1-9.15 caused block requests

Ortal November 21, 2018 01:47PM

Re: upgrade to 1-9.15 caused block requests

Maxim Dounin November 21, 2018 02:28PM

Re: upgrade to 1-9.15 caused block requests

Ortal November 22, 2018 07:15AM

Re: upgrade to 1-9.15 caused block requests

Maxim Dounin November 22, 2018 08:40AM



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