Tuesday, February 11, 2014

Splunk monitors machine data There are some concepts specific to Splunk. We briefly review these now. Index time processing : Splunk reads data from a source such as a file or a port and classifies that source into a source type. Data is broken into events that consist of single or multiple lines and writes each event into an index on disk, for later retrieval with a search.
When search starts, events are retrieved and classified based on eventtypes and the matching events are transformed to generate reports and displayed on dashboards.
By default, the events go into a main index unless a specified index is created or stored.
Fields are searchable name/value pairings in event data - usually the default fields are host, source and sourcetype. Tags are aliases to field values. Event types are dynamic tags attached to an event. Saved Splunk objects such as savedsearches, eventtypes, reports and tags are not only persisted but also secured with permissions based on users and roles. Thus events are enriched before indexing. When sets of events are grouped into one, they are called transactions.
Apps are a collection of splunk configurations, object and code. They help the user in organization of targeted activities.
Splunk instances can work in three different modes - forwarder, indexer and search head. A forwarder is a version of Splunk that allows you to send data to a central Splunk indexer or a group of indexers. An indexer provides indexing capability for local and remote data. An indexer is usually added for every 50-100 GB per day depending on search load. A Splunk search head is typically added for every 10-20 active users depending on searches.
One of the sources for machine data is message queuing. This is particularly interesting because message queues are increasingly being used as the backbone of logging architectures for applications. Subscribing to these message queues is a good way to debug problems in complex applications. As the Exploring Splunk book mentions, you can see exactly what the next component down the chain received from the prior component. However, the depth of support to subscribe to message queues and on different operating system varies. At the very least, transactional and non-transactional message queues on Windows could be supported directly out of the box. 

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