Hello Andrew,
Thank you for your answer!
I tried setting my header in r->upstream->headers_in but unfortunately, it
seems the headers ngx_list_t isn't initialized yet at this point, and thus I
end up with a crash in ngx_list_push(). I wish I could just initialize it
myself, but it would most likely get overwritten when the actual initialization
takes place.
Thanks,
Maxime
________________________________________
From: nginx-devel [nginx-devel-boun...@nginx.org] on behalf of Andrew Hutchings
[ahutchi...@nginx.com]
Sent: Monday, October 12, 2015 6:04 PM
To: nginx-devel@nginx.org
Subject: Re: Setting a custom header on a proxied request
Hi Maxime,
I could be wrong here (I'm not an expert at this section of code), but I
believe what you need to set is:
r->upstream->headers_in
If this doesn't work please let me know and I'll build a test to try it
out here.
Kind Regards
Andrew
On 12/10/15 15:12, Maxime Henrion wrote:
> Hi all,
>
>
> I'm currently writing an nginx module that sends a number of subrequests to
> upstream servers based on application logic, and then aggregates the results
> and send them back. That part currently works just fine, thanks to the help I
> was given here in the past.
>
> However, I am now trying to add a custom header to the request that is being
> proxied and currently failing at it. For various technical reasons, I need to
> add a header that contains the IP address and port (from the point of view of
> nginx) of the upstream server currently being contacted. In order to get at
> that address, I have hooked my module into the peer selection mechanism, much
> like the keepalive, ip_hash modules and others do. So far so good, I get at
> that address and can log it just fine. However, I can't seem to be able to
> add it as a header to my request.
>
> Here's my init_peer callback :
>
> static ngx_int_t
> ngx_http_dispatcher_upstream_init_peer(ngx_http_request_t *r,
> ngx_http_upstream_srv_conf_t *us)
> {
> ngx_http_dispatcher_upstream_peer_data_t *dp;
> ngx_http_dispatcher_srv_conf_t *dscf;
> ngx_int_t rc;
>
> dscf = ngx_http_conf_upstream_srv_conf(us,
> ngx_http_dispatcher_module);
>
> dp = ngx_palloc(r->pool,
> sizeof(ngx_http_dispatcher_upstream_peer_data_t));
> if (dp == NULL) {
> return NGX_ERROR;
> }
>
> rc = dscf->original_init_peer(r, us);
> if (rc != NGX_OK) {
> return rc;
> }
>
> dp->request = r;
> dp->data = r->upstream->peer.data;
> dp->original_get_peer = r->upstream->peer.get;
> dp->original_free_peer = r->upstream->peer.free;
>
> r->upstream->peer.data = dp;
> r->upstream->peer.get = ngx_http_dispatcher_upstream_get_peer;
> r->upstream->peer.free = ngx_http_dispatcher_upstream_free_peer;
>
> #if (NGX_HTTP_SSL)
> dp->original_set_session = r->upstream->peer.set_session;
> dp->original_save_session = r->upstream->peer.save_session;
> r->upstream->peer.set_session =
> ngx_http_dispatcher_upstream_set_session;
> r->upstream->peer.save_session =
> ngx_http_dispatcher_upstream_save_session;
> #endif
>
> return NGX_OK;
> }
>
> Note that I save the pointer to the ngx_http_request_t object in my peer data
> structure to access it later. Now here's my peer selection hook :
>
> static ngx_int_t
> ngx_http_dispatcher_upstream_get_peer(ngx_peer_connection_t *pc, void *data)
> {
> ngx_http_dispatcher_upstream_peer_data_t *dp = data;
> u_char addrbuf[NGX_SOCKADDR_STRLEN];
> ngx_http_request_t *r;
> ngx_table_elt_t *h;
> ngx_str_t peeraddr;
> ngx_int_t rc;
>
> rc = dp->original_get_peer(pc, dp->data);
> if (rc != NGX_OK) {
> return rc;
> }
>
> peeraddr.data = addrbuf;
> peeraddr.len = ngx_sock_ntop(pc->sockaddr, pc->socklen, addrbuf,
> sizeof(addrbuf), 1);
>
> ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
> "Selected peer address is: %V", &peeraddr);
>
> r = dp->request;
>
> h = ngx_list_push(&r->headers_in.headers);
> if (h == NULL) {
> return NGX_ERROR;
> }
> h->hash = 1;
> ngx_str_set(&h->key, "X-Shard-Addr");
> h->value.data = ngx_pstrdup(r->pool, &peeraddr);
> if (h->value.data == NULL) {
> return NGX_ERROR;
> }
>
> h->value.len = peeraddr.len;
>
> return NGX_OK;
> }
>
> So after getting at the actual address we're forwarding our request to, I try
> to add a custom header to r->headers_in, on the request object that I saved
> in my peer data.
>
> I suspect I'm not actually dealing with the correct request here, because no
> matter what I try, I can't get this code to actually alter the headers of the
> forwarded request in any way.
>
> Any help would be greatly appreciated!
> Thanks,
> Maxime
> _______________________________________________
> nginx-devel mailing list
> nginx-devel@nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx-devel
>
--
Andrew Hutchings (LinuxJedi)
Senior Developer Advocate, Nginx Inc.
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