pvc/health-daemon/plugins/zkpr

#!/usr/bin/env python3

# zkpr.py - PVC Monitoring example plugin for Zookeeper
# Part of the Parallel Virtual Cluster (PVC) system
#
#    Copyright (C) 2018-2024 Joshua M. Boniface <joshua@boniface.me>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, version 3.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <https://www.gnu.org/licenses/>.
#
###############################################################################

# This script provides an example of a PVC monitoring plugin script. It will create
# a simple plugin to check the Zookeeper instance on the node for operation.

# This script can thus be used as an example or reference implementation of a
# PVC monitoring pluginscript and expanded upon as required.

# A monitoring plugin script must implement the class "MonitoringPluginScript" which
# extends "MonitoringPlugin", providing the 3 functions indicated. Detailed explanation
# of the role of each function is provided in context of the example; see the other
# examples for more potential uses.

# WARNING:
#
# This script will run in the context of the node daemon keepalives as root.
# DO NOT install untrusted, unvetted plugins under any circumstances.


# This import is always required here, as MonitoringPlugin is used by the
# MonitoringPluginScript class
from pvchealthd.objects.MonitoringInstance import MonitoringPlugin


# A monitoring plugin script must always expose its nice name, which must be identical to
# the file name
PLUGIN_NAME = "zkpr"


# The MonitoringPluginScript class must be named as such, and extend MonitoringPlugin.
class MonitoringPluginScript(MonitoringPlugin):
    def setup(self):
        """
        setup(): Perform special setup steps during node daemon startup

        This step is optional and should be used sparingly.

        If you wish for the plugin to not zkpr in certain conditions, do any checks here
        and return a non-None failure message to indicate the error.
        """

        pass

    def run(self, coordinator_state=None):
        """
        run(): Perform the check actions and return a PluginResult object

        The {coordinator_state} can be used to check if this is a "primary" coordinator, "secondary" coordinator, or "client" (non-coordinator)
        """

        # Run any imports first
        from kazoo.client import KazooClient, KazooState

        zk_conn = None

        # Set the health delta to 0 (no change)
        health_delta = 0
        # Craft a message that can be used by the clients
        message = "Successfully connected to Zookeeper on localhost"

        # Check the Zookeeper connection
        try:
            zk_conn = KazooClient(hosts=[f"{self.this_node.name}:2181"], timeout=1, read_only=True)
            zk_conn.start(timeout=1)
            data = zk_conn.get('/schema/version')
        except Exception as e:
            health_delta = 50
            message = f"Failed to connect to Zookeeper: {e}"
        finally:
            if zk_conn is not None:
                zk_conn.stop()
                zk_conn.close()

        # Set the health delta in our local PluginResult object
        self.plugin_result.set_health_delta(health_delta)

        # Set the message in our local PluginResult object
        self.plugin_result.set_message(message)

        # Return our local PluginResult object
        return self.plugin_result

    def cleanup(self):
        """
        cleanup(): Perform special cleanup steps during node daemon termination

        This step is optional and should be used sparingly.
        """

        pass