Re: sub filter‘s bug?

[Simon Liu]

thanks Maxim!

my patch is mistake.

but when remove http_ssi_module , sub filter module may  log  alert:

 "the http output chain is empty while sending response to client."

because sub filter module need ngx_http_postpone_filter's code :

 if (r->postponed == NULL) {

        if (in || c->buffered) {
            return ngx_http_next_filter(r->main, in);
        }

        return NGX_OK;
    }

this code is needed by subrequest only?  i think sub filter is needed too.


On Tue, Sep 21, 2010 at 7:57 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:

> Hello!
>
> On Tue, Sep 21, 2010 at 05:08:08PM +0800, Simon Liu wrote:
>
> > i find this result  is cause by postpone filter is removed. because i
> > use --without-http_ssi_module config nginx. and i read nginx config find
> > this   in  auto/modules:
> >
> > if [ $HTTP_SSI = YES ]; then
> >     HTTP_POSTPONE=YES
> > fi
> >
> >
> > if [ $HTTP_ADDITION = YES ]; then
> >     HTTP_POSTPONE=YES
> > fi
> >
> > and why  postpone is yes when ssi or addition module is on ?
>
> Postpone filter is used to order data sent by subrequests.  It
> shouldn't be needed when no subrequests are used.
>
> > and then i debug nginx find some code in ngx_http_postpone_filter method
> :
> >
> >     if (r->postponed == NULL) {
> >
> >         if (in || c->buffered) {
> >             return ngx_http_next_filter(r->main, in);
> >         }
> >
> >         return NGX_OK;
> >     }
> >
> > therefore if no postpone module, sub filter module may emerge the result
> in
> > my previous email  .
> >
> > On Wed, Sep 15, 2010 at 11:00 AM, Simon Liu <simohayha.bobo at gmail.com
> >wrote:
> >
> > > my nginx version is 0.7.67.
> > >
> > > I test nginx's sub filter, there have some alert log in error log:
> > >
> > > *the http output chain is empty while sending response to client.*
> > > *
> > > *
> > > and  i debug nginx , and then found this is cause by sub filter. so  i
> read
> > >  sub filter's source.
> > >
> > > in  ngx_http_sub_body_filter:
> > >
> > >   *  if (ctx->once && (ctx->buf == NULL || ctx->in == NULL)) {*
> > > *
> > > *
> > > *        if (ctx->busy) {*
> > > *            if (ngx_http_sub_output(r, ctx) == NGX_ERROR) {*
> > > *                return NGX_ERROR;*
> > > *            }*
> > > *        }*
> > > *
> > > *
> > > *        return ngx_http_next_body_filter(r, in);*
> > > *    }*
> > >
> > > i found when  sub_filter_once is on , after  text have replaced . and
> the
> > > second enter ngx_http_sub_body_filter.
> > > At the moment when in is null,ctx->busy is not null,and so
> *ngx_http_sub_output
> > >  may send  *the rest of* buf  completely**,  therefore in
>  **ngx_http_next_body_filter
> > > will log alert log : the http output chain is empty while sending
> response
> > > to client. *
> > > *
> > > *
> > > *i*n conclusion I *think  there should add a *judgement that in is
> whether
> > > or not NULL.
> > > *
> > > *
> > > *this is my patch:*
> > > *
> > > *
> > > *
> > > --- nginx-0.7.67/src/http/modules/ngx_http_sub_filter_module.c
> 2009-10-26
> > > 23:54:29.000000000 +0800
> > > +++ nginx-0.7.67_new/src/http/modules/ngx_http_sub_filter_module.c
> 2010-09-15
> > > 10:14:04.996666685 +0800
> > > @@ -187,16 +187,16 @@ ngx_http_sub_body_filter(ngx_http_reques
> > >      }
> > >
> > >      if (ctx->once && (ctx->buf == NULL || ctx->in == NULL)) {
> > >
> > >          if (ctx->busy) {
> > > -            if (ngx_http_sub_output(r, ctx) == NGX_ERROR) {
> > > -                return NGX_ERROR;
> > > -            }
> > > +            rc = ngx_http_sub_output(r, ctx);
> > >          }
> > >
> > > -        return ngx_http_next_body_filter(r, in);
> > >  +        if (rc != NGX_ERROR && in != NULL)
> > > +            return ngx_http_next_body_filter(r, in);
> > > +        return rc;
>
> This will use uninitialized rc when no ctx->busy.
>
> Maxim Dounin
>
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