[master] 3eba5f8 warning and advise about backend proxy connections
Nils Goroll
nils.goroll at uplex.de
Mon Apr 9 12:24:10 UTC 2018
commit 3eba5f8ce18e3d8e06a7016f9099e689f5186bc7
Author: Nils Goroll <nils.goroll at uplex.de>
Date: Mon Apr 9 14:23:06 2018 +0200
warning and advise about backend proxy connections
Ref #2622
diff --git a/doc/sphinx/reference/vcl.rst b/doc/sphinx/reference/vcl.rst
index d2eec3d..d2263dc 100644
--- a/doc/sphinx/reference/vcl.rst
+++ b/doc/sphinx/reference/vcl.rst
@@ -252,6 +252,21 @@ parameters. The following attributes are available:
The PROXY protocol version Varnish should use when connecting to
this backend. Allowed values are ``1`` and ``2``.
+ *Notice* this setting will lead to backend connections being used
+ for a single request only (subject to future improvements). Thus,
+ extra care should be taken to avoid running into failing backend
+ connections with EADDRNOTAVAIL due to no local ports being
+ available. Possible options are:
+
+ * Use additional backend connections to extra IP addresses or TCP
+ ports
+
+ * Increase the number of available ports (Linux sysctl
+ ``net.ipv4.ip_local_port_range``)
+
+ * Reuse backend connection ports early (Linux sysctl
+ ``net.ipv4.tcp_tw_reuse``)
+
``.max_connections``
Maximum number of open connections towards this backend. If
Varnish reaches the maximum Varnish it will start failing
More information about the varnish-commit
mailing list