Implementation specifics

The clinfo daemon is an SNMP-based monitor. SNMP is a industry-wide set of standards for monitoring and managing TCP/IP-based networks. SNMP includes a protocol, a database specification, and sets of data objects.

The sets of data objects form a Management Information Base (MIB). SNMP provides a standard MIB that includes information such as IP addresses and the number of active TCP connections. The actual MIB definitions are encoded into the agents running on a system. The standard SNMP agent in AIX® is the SNMP daemon, snmpd.

Programmers use SNMP operations to implement programs that will monitor and manage networks. These programs can receive information about the state of a network from snmpd, and pass the information on to clients and applications.

SNMP can be extended using the SNMP Multiplexing (SMUX) protocol to include enterprise-specific MIBs that contain information relating to a discrete environment or application. A management agent (a SMUX peer daemon) retrieves and maintains information about the objects defined in its MIB, and makes this information available to a specialized network monitor or network management station.

The PowerHA® SystemMirror® software provides this SMUX peer function through the Cluster manager daemon. The clinfo daemon retrieves this information from the PowerHA SystemMirror MIB (and indirectly) through the Cluster Manager.

The Clinfo API library (in all its variations) interacts with the clinfo daemon to provide access to the cluster information. Although the same information is available directly through SNMP, the Clinfo library provides a greatly simplified programming model allowing client programs to avoid the complexities of the SNMP API. The Clinfo API provides routines to retrieve all information related to cluster entities like nodes or resource groups (SNMP requires you to fetch these items one at a time) and routines to register for specific cluster events (SNMP requires traps to implement similar function). Variations of the library—C, C++, thread safe, and so forth—provide a consistent model for a variety of runtime environments.

The clinfo daemon and library can run on PowerHA SystemMirror cluster nodes or on a non-cluster node, provided the daemon can access SNMP on a cluster node through TCP/IP.