Implement "return(retry)" in vcl_backend_error{}

bin/varnishd/cache/cache_fetch.c

@@ -666,7 +666,20 @@ vbf_stp_error(struct worker *wrk, struct busyobj *bo)
 
 	AZ(VSB_finish(bo->synth_body));
 
-	xxxassert(wrk->handling == VCL_RET_DELIVER);
+	if (wrk->handling == VCL_RET_RETRY) {
+		VSB_delete(bo->synth_body);
+		bo->synth_body = NULL;
+	    	if (bo->retries++ < cache_param->max_retries) {
+			return (F_STP_RETRY);
+		}
+		bo->synth_body = NULL;
+		HSH_Fail(bo->fetch_objcore);
+		VBO_setstate(bo, BOS_FAILED);
+		HSH_Complete(bo->fetch_objcore);
+		return (F_STP_DONE);
+	}
+
+	assert(wrk->handling == VCL_RET_DELIVER);
 
 	if (vbf_beresp2obj(bo)) {
 		VBO_setstate(bo, BOS_FAILED);

bin/varnishtest/tests/c00061.vtc

+varnishtest "retry in vcl_backend_error"
+
+varnish v1 -vcl {
+
+	backend b1 { .host = "${bad_ip}"; }
+
+	sub vcl_backend_error {
+		return (retry);
+	}
+
+	sub vcl_error {
+		set obj.status = 504;
+	}
+} -start
+
+varnish v1 -cliok "param.set debug +syncvsl"
+varnish v1 -cliok "param.set connect_timeout 1"
+varnish v1 -cliok "param.set max_retries 2"
+
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 504
+} -run