Hi all,

Does limit_rate, which is in write filter module, work right when many subrequests exist?
I meet a problem with limit_rate for many subrequests. Here is the problem.

1. limit_rate works like this:
a) after sending data, it will set wev->delayed which disable data sending, and sleep for a while(add_timer);
b) when timedout, the wev handler will clear wev->delayed, to enable data sending.
For example, the handler may like this;

src/http/ngx_http_upstream.c:ngx_http_upstream_process_downstream()

2361 if (wev->timedout) {

2363 if (wev->delayed) {

2367 wev->delayed = 0;

2389 }

2395 }


2. but 1 wev (write event) corresponds to 1 connection; while 1 (downstream) connection may has many subrequests.
so when wev timedout, wev gets the active request of the connection, like this:


src/http/ngx_http_request.c:ngx_http_request_handler()

1724 c = ev->data;

1725 r = c->data;

1726

1733 if (ev->write) {

1734 r->write_event_handler(r);

1737 } else {

1738 r->read_event_handler(r);

1739 }





3. The problem is that: the active request of this connection maybe not the one who added the timer. which means that the active request of the connection changes before timedout. So its write_event_handler maybe not the one expected. For example, if the active request's write_event_handler is happened to be ngx_http_request_empty_handler(), which is set in ngx_http_core_content_phase(), then the handler doesn't clear the wev->delayed.So the data sending in write filter module will never be enabled again.



Is my analysis right? Does limit_rate work right for many subrequests?



I hope I made myself understood.

Thanks,

Wu
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