Changelog for Nagios Core 4.0

Nagios  Nagios Core 4.0 released last Friday, 22th de September. From the release note, this release is much like for performance optimization. In this major release, nagios has a lot of architecture changes. Here are my highlighted ones:

  • Core Workers – Core workers are lightweight processes whose only job is to perform checks. Because they are smaller they spawn much more quickly than the the old process which forked the full Nagios Core. In addition, they communicate with the main Nagios Core process using in-memory techniques, eliminating the disk I/O latencies that could previously slow things down, especially in large installations.
  • Configuration Verification – Configuration verification has been improved so that each configuration item is verified only once. Previously configuration verification was an O(n2) operation.
  • Event Queue – The event queue now uses a data structure that has O(log n) insertion times versus the O(n) insertion time previously. This means that inserting events into the queue uses much less CPU than in Nagios Core 3.

This release enables service dependency check. Services now support a parents attribute. A service parent performs a function similar to host parents and can be used in place of service dependencies in simple circumstances.

Query Handler is new in v4.0 as well. Query handler is a general purpose communication mechanism that allows external entities to communicate with Nagios Core in a well-defined manner. As of this writing, all communication with the query handler takes place through a Unix-domain socket whose location is defined by the query_socket configuration variable.

There are currently 5 built-in query handlers.

  • core – provides Nagios Core management and information
  • wproc – provides worker process registration, management and information
  • nerd – provides a subscription service to the Nagios Event Radio Dispatcher (NERD)
  • help – provides help for the query handler
  • echo – implements a basic query handler that simply echoes back the queries sent to it

A full-version release note is available here:

Basically, Nagios 4.0 learns from Zabbix, which will make it more powerful.

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