[4.0] 51cee0b Don't attempt to run the fetch in the request thread if there are no threads available in the pool, fail the fetch and count it.

[Lasse Karstensen]

commit 51cee0bff0072ef2d2b39be77b92f475694540d4
Author: Martin Blix Grydeland <martin at varnish-software.com>
Date:   Tue Nov 18 13:58:29 2014 +0100

    Don't attempt to run the fetch in the request thread if there are no threads available in the pool, fail the fetch and count it.
    
    Fixes #1620
    Fixes #1621
    
    (cherry picked from commit 969674dcb3b4d430a38b7f1b1e41199b25cc8491)

diff --git a/bin/varnishd/cache/cache_fetch.c b/bin/varnishd/cache/cache_fetch.c
index 9478edc..18c937d 100644
--- a/bin/varnishd/cache/cache_fetch.c
+++ b/bin/varnishd/cache/cache_fetch.c
@@ -952,9 +952,13 @@ VBF_Fetch(struct worker *wrk, struct req *req, struct objcore *oc,
 	bo->fetch_task.priv = bo;
 	bo->fetch_task.func = vbf_fetch_thread;
 
-	if (Pool_Task(wrk->pool, &bo->fetch_task, POOL_QUEUE_FRONT))
-		vbf_fetch_thread(wrk, bo);
-	if (mode == VBF_BACKGROUND) {
+	if (Pool_Task(wrk->pool, &bo->fetch_task, POOL_QUEUE_FRONT)) {
+		wrk->stats.fetch_no_thread++;
+		(void)vbf_stp_fail(req->wrk, bo);
+		if (bo->ims_obj != NULL)
+			(void)HSH_DerefObj(&wrk->stats, &bo->ims_obj);
+		VBO_DerefBusyObj(wrk, &bo);
+	} else if (mode == VBF_BACKGROUND) {
 		VBO_waitstate(bo, BOS_REQ_DONE);
 	} else {
 		VBO_waitstate(bo, BOS_STREAM);
diff --git a/include/tbl/vsc_f_main.h b/include/tbl/vsc_f_main.h
index f93a86f..02e051c 100644
--- a/include/tbl/vsc_f_main.h
+++ b/include/tbl/vsc_f_main.h
@@ -237,8 +237,12 @@ VSC_F(fetch_304,		uint64_t, 1, 'c', info,
 	"beresp with no body because of 304 response."
 )
 VSC_F(fetch_failed,		uint64_t, 1, 'c', info,
-    "Fetch body failed",
-	"beresp body fetch failed."
+    "Fetch failed (all causes)",
+	"beresp fetch failed."
+)
+VSC_F(fetch_no_thread,		uint64_t, 1, 'c', info,
+    "Fetch failed (no thread)",
+	"beresp fetch failed, no thread available."
 )
 
 /*---------------------------------------------------------------------