server_forward_retries directive is ignored if request is forwarded to inactive server connection

[vankoven]

When a request is sent to backend in tfw_http_req_fwd_send(), an error may happen in ss_send(), e.g. socket is inactive. In this case the request is dropped and 500 error is returned to client:

tempesta/tempesta_fw/http.c

Lines 1103 to 1104 in 036a0f1

	tfw_http_req_err(srv_conn, req, eq, 500,
	"request dropped: forwarding error");

You can see warnings in the system log:

[ 6627.198664] [tempesta] Warning: request dropped: forwarding error, status 500: ::ffff:c0a8:7a01
[ 6641.007429] [tempesta] Warning: request dropped: forwarding error, status 500: ::ffff:c0a8:7a01
[ 6645.200972] [tempesta] Warning: request dropped: forwarding error, status 500: ::ffff:c0a8:7a01
[ 6668.633026] [tempesta] Warning: request dropped: forwarding error, status 500: ::ffff:c0a8:7a01
[ 6674.709124] [tempesta] Warning: request dropped: forwarding error, status 500: ::ffff:c0a8:7a01
[ 6676.332363] [tempesta] Warning: request dropped: forwarding error, status 500: ::ffff:c0a8:7a01

The tfw_http_req_fwd_send() function doesn't honour server_forward_retries directive and drops the request on very first ss_send() failure. Instead Tempesta must increment message retry count on failure and drop request only in tfw_http_req_evict_retries() function.

tempesta/tempesta_fw/http.h

Line 499 in 036a0f1

unsigned short retries;