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## SNMP MIB and Script Extension

This extension is meant to be used with Ambari 2.1 or later and uses the capabilities introduced in AMBARI-9919 to delegate alerts to an external script.

In this case, the external script `snmp_mib_script.sh` is used to invoke the `snmptrap` command from the `net-snmp` Linux packages to issue an SNMP trap to a specific destination.

In order to wire this script up to Ambari the following procedures should be followed as the root user, or with a user with equivalent sudo access:

Install SNMP Utils

    yum install net-snmp net-snmp-utils net-snmp-libs -y

Make SNMP Utils aware of the Apache Ambari MIB

    cp APACHE-AMBARI-MIB.txt /usr/share/snmp/mibs

Startup a simple SNMP trap daemon to log all traps to the `/tmp/traps.log` file for testing purposes.

    nohup snmptrapd -m ALL -A -n -Lf /tmp/traps.log &

Invoke a test trap to ensure that the snmptrapd is logging appropriately to `/tmp/traps.log` and the Apache Ambari MIB is being respected.

    snmptrap -v 2c -c public localhost '' APACHE-AMBARI-MIB::apacheAmbariAlert alertDefinitionName s "definitionName" alertDefinitionHash s "definitionHash" alertName s "name" alertText s "text" alertState i 0 alertHost s "host" alertService s "service" alertComponent s "component"

You should see this in /tmp/traps.log.

    2015-09-03 05:14:30 UDP: [127.0.0.1]:45431->[127.0.0.1] [UDP: [127.0.0.1]:45431->[127.0.0.1]]:
    DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (15638958) 1 day, 19:26:29.58	SNMPv2-MIB::snmpTrapOID.0 = OID: APACHE-AMBARI-MIB::apacheAmbariAlert	APACHE-AMBARI-MIB::alertDefinitionName = STRING: "definitionName"	APACHE-AMBARI-MIB::alertDefinitionHash = STRING: "definitionHash"	APACHE-AMBARI-MIB::alertName = STRING: "name"	APACHE-AMBARI-MIB::alertText = STRING: "text"	APACHE-AMBARI-MIB::alertState = INTEGER: ok(0)	APACHE-AMBARI-MIB::alertHost = STRING: "host"	APACHE-AMBARI-MIB::alertService = STRING: "service"	APACHE-AMBARI-MIB::alertComponent = STRING: "component"

Once that output has been validated, it's time to make Ambari aware of the script to begin sending SNMP traps that conform to it.

Create a file that contains the script, named `/tmp/snmp_mib_script.sh`, in this example.  It's recommended to create this file in a more permanent directory for actual use.

Add the following line to the `/etc/ambari-server/conf/ambari.properties` file

    org.apache.ambari.contrib.snmp.script=/tmp/snmp_mib_script.sh

Restart Ambari using `ambari-server restart`

Now, we need to use the API to add an alert target for this script.  The following content needs to be POST'd to /api/v1/alert_targets.

    {
      "AlertTarget": {
        "name": "SNMP_MIB",
        "description": "SNMP MIB Target",
        "notification_type": "ALERT_SCRIPT",
        "global": true,
        "properties": {
            "ambari.dispatch-property.script": "org.apache.ambari.contrib.snmp.script"
         }
      }
    }

You'll notice the link between the alert target and the script is this property reference: `org.apache.ambari.contrib.snmp.script`.

At this point each alert will send an SNMP trap to the local trap daemon and an entry will be recorded in `/tmp/traps.log`.
