I've enabled redis for session, have the latest extension and lib code from github, and I'm noticing some requests take around 30 seconds - and this is happening pretty frequently, and it's always redis which is to blame.
Here are 3 transaction traces from newrelic, they look pretty much the same to me: https://i.stack.imgur.com/7ceh1.png
I am using the following settings in redis:
<redis_session> <host>127.0.0.1</host> <port>6379</port> <password></password> <timeout>2.5</timeout> <persistent></persistent> <db>2</db> <compression_threshold>2048</compression_threshold> <compression_lib>lzf</compression_lib> <log_level>4</log_level> <!-- maximum number of processes that can wait for a lock on one session; for large production clusters, set this to at least 10% of the number of PHP processes --> <max_concurrency>12</max_concurrency> <!-- seconds to wait for a session lock in the frontend; not as critical as admin --> <break_after_frontend>5</break_after_frontend> <break_after_adminhtml>30</break_after_adminhtml> <!-- Bots get shorter session lifetimes. 0 to disable --> <bot_lifetime>7200</bot_lifetime> </redis_session>
At the moment, only one frontend server is being used for magento.