IHS ServerIOTimeout

There can be a number of reasons for seeing a message like the one below in your http_plugin.log

ERROR: ws_common: websphereHandleRequest: Failed to execute the transaction to 'myClusterMember' on host 'myHost'; will try another one

... but a common reason is that ServerIOTimeout in plugin-cfg.xml is set too low 

To verify, set your log level to trace (i.e in plugin-cfg.xml change LogLevel from "error" to "trace"), wait for RefreshInterval (or bounce IHS if you're impatient) and look for the following message...

lib_rio: wait_on_socket: ServerIOTimeout fired.

Point to note.. if you are seeing this message in an environment where you have SSL Client Authentication enabled (aka 2-way SSL) chances are that you'll also be seeing GSK errors (look for PARTNER CERTIFICATE). I saw this and spend a while chasing down a non-existent trust issue. I then realised that the reason this was happening is because (I think) that the ServerIOTimeout was firing during the SSL handshake.

ps... don't forget to set your LogLevel back to "error"