Today I have added the capability to specify asynchronous replication support and timeout settings to omelasticsearch. Code-wise it's a small change - it just passed the required parameters to ElasticSearch via the proper REST URL parameters. By default, both parameters are not set, that means default timeout and synchronous replication.
To set parameters, use
... other params ...
If you leave "asyncrepl" out or set it to "off", synchronous replication is used. For greatest flexiblity, the value of the "timeout" parameter is not checked. While this enables you to use anything ElasticSearch supports, invalid values can not be detected by omelasticsearch and thus will cause all inserts to fail (or misbehave). Note that some basic integrity checking is done, but we do not go great length here. So use with care.