Core group Discovery Protocol

When a core group member starts, no connections to other core group members exist. The task that runs the Discovery Protocol for this core group member starts as part of the core group members startup procedure. The Discovery Protocol establishes network connectivity with the other members of the core group. This task runs at regularly scheduled intervals as long as the core group member is active.

The Discovery Protocol retrieves the list of core group members and the associated network information from the WAS configuration settings. The Discovery Protocol then attempts to open network connections to all of the other core group members. At periodic intervals, the Discovery Protocol recalculates the set of unconnected members and attempts to open connections to those members.

When a connection is made to another core group member, the Discovery Protocol notifies the View Synchrony Protocol, and logs this event as an informational message, similar to the following message, in the SystemOut.log file

DCSV1032I: DCS Stack DefaultCoreGroup at Member MyCell\anzio\nodeagent: 
Connected a defined member MyCell\anzioCellManager\dmgr.

Connections can fail at any time for a variety of reasons. The Failure Detection Protocol detects connection failures and notifies the Discovery Protocol. The Discovery Protocol then attempts to open a new network connection to that member at the next scheduled interval.

The interval at which the Discovery Protocol runs is configurable. For Versions 6.0 and 6.0.1, the default is 15 seconds. For v6.2 and higher, the default is 30 seconds. Use the IBM_CS_UNICAST_DISCOVERY_INTERVAL_SECS core group custom property to change this setting.

The amount of CPU cycles that the Discovery Protocol task consumes is proportional to the number of core group members that are stopped or unreachable. The CPU cycles that the Discovery Protocol task consumes is negligible at the default settings.



Related concepts
Core groups (high availability domains) Related tasks
Configuring the Discovery Protocol for a core group Related reference
Core group custom properties

 



 

 

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