[6.0] 15f5aa3d0 vtc sweep through tight backend workspace conditions

[Dridi Boukelmoune]

commit 15f5aa3d0d2add1a71b8800ce76709f557e29f70
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Thu Apr 19 09:40:23 2018 +0200

    vtc sweep through tight backend workspace conditions
    
    Ref: #2645

diff --git a/bin/varnishtest/tests/r02645.vtc b/bin/varnishtest/tests/r02645.vtc
new file mode 100644
index 000000000..d66573747
--- /dev/null
+++ b/bin/varnishtest/tests/r02645.vtc
@@ -0,0 +1,25 @@
+varnishtest "sweep through tight backend workspace conditions"
+
+server s1 -repeat 100 {
+	rxreq
+	send "HTTP/1.1 200 OK\r\nTransfer-encoding: chunked\r\n\r\n00000004\r\n1234\r\n00000000\r\n\r\n"
+} -start
+
+varnish v1 -vcl+backend {
+	import vtc;
+	import std;
+	sub vcl_recv {
+		return (pass);
+	}
+	sub vcl_backend_fetch {
+		vtc.workspace_alloc(backend, -4 *
+			(std.integer(bereq.xid, 1002) - 1000) / 2);
+	}
+} -start
+
+client c1 -repeat 100 {
+	txreq -url "/"
+	# some responses will fail (503), some won't. All we care
+	# about here is the fact that we don't panic
+	rxresp
+} -run