org.opennms.netmgt.poller.monitors
Class DnsMonitor

java.lang.Object
  org.opennms.netmgt.poller.monitors.AbstractServiceMonitor
      org.opennms.netmgt.poller.monitors.DnsMonitor

All Implemented Interfaces:

ServiceMonitor

@Distributable
public final class DnsMonitor
extends AbstractServiceMonitor

This class is designed to be used by the service poller framework to test the availability of the DNS service on remote interfaces. The class implements the ServiceMonitor interface that allows it to be used along with other plug-ins by the service poller framework.

Author:

Tarus Balog , OpenNMS

Constructor Summary

DnsMonitor()

Method Summary

PollStatus

poll(MonitoredService svc, Map<String,Object> parameters) This method is the heart of the plug-in monitor.

Methods inherited from class org.opennms.netmgt.poller.monitors.AbstractServiceMonitor

initialize, initialize, log, logDown, logDown, logUp, release, release

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DnsMonitor

public DnsMonitor()

Method Detail

poll

public PollStatus poll(MonitoredService svc,
                       Map<String,Object> parameters)

This method is the heart of the plug-in monitor. Each time an interface requires a check to be performed as defined by the scheduler the poll method is invoked. The poll is passed the interface to check

By default when the status transition from up to down or vice versa the framework will generate an event. Additionally, if the polling interval changes due to an extended unavailability, the framework will generate an additional down event. The plug-in can suppress the generation of the default events by setting the suppress event bit in the returned integer.

Poll the specified address for DNS service availability.

During the poll an DNS address request query packet is generated for hostname 'localhost'. The query is sent via UDP socket to the interface at the specified port (by default UDP port 53). If a response is received, it is parsed and validated. If the DNS lookup was successful the service status is set to SERVICE_AVAILABLE and the method returns.

Specified by:

poll in interface ServiceMonitor

Specified by:

poll in class AbstractServiceMonitor

Parameters:

svc - TODO

parameters - The package parameters (timeout, retry, etc...) to be used for this poll.

Returns:

The availability of the interface and if a transition event should be suppressed.

See Also:

PollStatus.SERVICE_AVAILABLE, PollStatus.SERVICE_UNAVAILABLE, PollStatus.SERVICE_AVAILABLE, PollStatus.SERVICE_UNAVAILABLE