Make timeout half the length of that used by Sprout / Homestead ...

src/memcached_backend.cpp

@@ -58,7 +58,11 @@ MemcachedBackend::MemcachedBackend(MemcachedConfigReader* config_reader,
   // timeout because libmemcached tries to connect to all servers sequentially
   // during start-up, and if any are not up we don't want to wait for any
   // significant length of time.
-  _options = "--CONNECT-TIMEOUT=10 --SUPPORT-CAS --POLL-TIMEOUT=250 --BINARY-PROTOCOL";
+  // Note that the poll timeout needs to be at most half the timeout used by
+  // the MemcachedStore (i.e. Sprout / Homestead when sending requests to us)
+  // to give us time to try a second replica if the request to the first replica
+  // times out.
+  _options = "--CONNECT-TIMEOUT=10 --SUPPORT-CAS --POLL-TIMEOUT=50 --BINARY-PROTOCOL";
 
   // Create an updater to keep the store configured appropriately.
   _updater = new Updater<void, MemcachedBackend>(this, std::mem_fun(&MemcachedBackend::update_config));