I'm not sure if this should be a ruby or docs ticket but as it relates to the release notes, I am raising it in the RUBY project.

The default op_timeout has changed from nil to 20 seconds.The specific change I am referring to is the following on lib/mongo/mongo_client.rb#L45:

    DEFAULT_OP_TIMEOUT   = 20

This change can cause unexpected applications failures when upgrading from a version of 1.11.1 or lower. As a result, it needs to be flagged more prominently in the release notes.

There is a simple code change to revert back to the previous behaviour:

connection  = MongoClient.new(host, port,{op_timeout:nil})