On 16/10/2015 13:20, Maxim Dounin wrote:
Hello!
On Fri, Oct 16, 2015 at 02:36:13AM +0100, Steven Hartland wrote:
I'm making changes to a filter module and when it detected an error it
returned NGX_ERROR however the response generated to the client isn't
the expected 500 internal server error I would have expected given said
return.
So the question is do filters have to manually call
ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR); or is it
expected that the upper layers should actually do the right thing and
ensure the client doesn't get a bad response generated from the current
state of r with no indication an error occurred?
In filters, it's already to late to return anything in case of
errors. In body filters, it's way too late - the response was
already partially sent. And in header filters there is a chance that
other filters allocated something response-specific, and an
attempt to return a different response will break things. So,
when you return NGX_ERROR from a filter, the connection is just
closed.
There are a few core filters which seem to contradict this;
range does:
return ngx_http_range_not_satisfiable(r, ctx);
while image does:
return ngx_http_filter_finalize_request(r,
&ngx_http_image_filter_module,
NGX_HTTP_UNSUPPORTED_MEDIA_TYPE);
The range filter is the one I was looking at, picking back up the work
you gave feedback on a while back with regards allow partial content
responses to be used to satisfy range requests.
During testing for failures I triggered the NGX_ERROR case here:
https://github.com/nginx/nginx/blob/master/src/http/modules/ngx_http_range_filter_module.c#L233
When I triggered this case client recieved an broken 200 response, where
as if I did finalise the request I could deliver a 500 response, so was
wondering if this would be correct in this situation?
If you absolutely must return an error from a filter - like, e.g.,
not modified filter do for 416 responses - there is a special
function to do this, ngx_http_filter_finalize_request(). It's
very fragile though, and I wouldn't recommend using it unless you
are sure you must do it.
Yer I found that later but seems my mail's been playing up today, so
sorry for the crossed replies.
Thanks for the feedback :)
Regards
Steve
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