The Talend Log Server is based on Elasticsearch. Elasticsearch is an open source search and analytics engine that makes data easy to explore.
The Talend Log Server will be installed outside the Talend Runtime Container and is optional for the Event Logging feature. But when the Talend Log Server is installed, the log data - even large amounts of log data - can be searched much more quickly and easily. And in the combination with the Event Logging Search Web Application, it is easier for users to find related data by different criteria including full text search.
For more information about the Talend Log Server, see the Talend Administration Center User Guide. And for more information about Elasticsearch, go to its web site: http://www.elasticsearch.org/.