Subrequests from body filters

[Marat Dakota]

It looks like I've figured out again, I see buffers flushed when they
contain \n character.

Sorry to bother.

--
Marat

On Mon, Mar 25, 2013 at 1:15 AM, Marat Dakota <dakota at brokenpipe.ru> wrote:
> It looks like I've figured out. When I set b->last_buf to 0 for all
> the buffers and to 1 for just actual last buffer, everything is ok.
>
> But then another question happens. Even if all the buffers have
> b->flush set to 1, I see my response only in one single chunk, after
> all the subrequests finished. How to actually flush the response
> buffer by buffer?
>
> --
> Marat
>
> On Sun, Mar 24, 2013 at 9:12 PM, Marat Dakota <dakota at brokenpipe.ru> wrote:
>> Hi,
>>
>> I'm writing a handler module. It makes subrequests and uses body
>> filter for subrequests.
>>
>> Here is simplified handler code:
>>
>> static ngx_int_t
>> ngx_http_my_handler(ngx_http_request_t *r) {
>>
>>     // ... Sending headers.
>>
>>     ngx_chain_t                 *out;
>>     ngx_buf_t                   *b;
>>
>>     out = ngx_alloc_chain_link(r->pool);
>>     b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
>>
>>     if (out == NULL || b == NULL) {
>>         return NGX_HTTP_INTERNAL_SERVER_ERROR;
>>     }
>>
>>     b->pos = "aaa";
>>     b->last = "aaa" + 3;
>>     b->memory = 1;
>>     b->last_buf = 1;
>>
>>     out->buf = b;
>>     out->next = NULL;
>>
>>     // ngx_http_my_subrequest() creates ngx_str_t from second argument
>> and calls ngx_http_subrequest().
>>     if (ngx_http_my_subrequest(r, "/uri1") != NGX_OK) {
>>         return NGX_ERROR;
>>     }
>>
>>     if (ngx_http_my_subrequest(r, "/uri2") != NGX_OK) {
>>         return NGX_ERROR;
>>     }
>>
>>     return ngx_http_output_filter(r, out);
>> }
>>
>>
>> Here is subrequest body filter:
>>
>> static ngx_int_t
>> ngx_http_my_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
>> {
>>     // ... Do something with subrequest's body in "in" argument.
>>
>>     ngx_chain_t                 *out;
>>     ngx_buf_t                   *b;
>>     ngx_chain_t                 *cl;
>>
>>     out = ngx_alloc_chain_link(r->pool);
>>     b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
>>
>>     if (out == NULL || b == NULL) {
>>         return NGX_HTTP_INTERNAL_SERVER_ERROR;
>>     }
>>
>>     // HERE BE DRAGONS.
>>
>>     b->pos = "bbb";
>>     b->last = "bbb" + 3;
>>     b->memory = 1;
>>     b->last_buf = 1;
>>
>>     out->buf = b;
>>     out->next = NULL;
>>
>>     // Discard subrequest's body.
>>     for (cl = in; cl; cl = cl->next) {
>>         cl->buf->pos = cl->buf->last;
>>         cl->buf->file_pos = cl->buf->file_last;
>>     }
>>
>>     // We just put "bbb" to main response for each call of this body filter.
>>     return ngx_http_output_filter(r->main, out);
>> }
>>
>> And everything works just fine. For example, if
>> ngx_http_my_body_filter is called twice for each (/uri1 and /uri2)
>> subrequest started from ngx_http_my_handler, the result will be
>> "aaabbbbbbbbbbbb".
>>
>> But if I replace "HERE BE DRAGONS" with a call to
>> ngx_http_my_subrequest(r->main, "/uri3"), let's suppose this
>> subrequest is being started only in second call of
>> ngx_http_my_body_filter for /uri1 subrequest started from
>> ngx_http_my_handler. The result will be "aaabbb", not
>> "aaabbbbbbbbbbbbbbbbbb" as I expect (and logs say all three
>> subrequests are processed ok).
>>
>> I guess my problem is about some magic with buffers and chains, but I
>> can't figure out what to fix and where.
>>
>> I would be thankful for any help.
>>
>> --
>> Marat