pvc/health-daemon/plugins/psql

149 lines
6.1 KiB
Python

#!/usr/bin/env python3
# psql.py - PVC Monitoring example plugin for Postgres/Patroni
# Part of the Parallel Virtual Cluster (PVC) system
#
# Copyright (C) 2018-2022 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 Patroni PostgreSQL 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 = "psql"
# 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.
"""
# Prepare the last coordinator state
self.last_coordinator_state = None
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 psycopg2 import connect
from json import loads as jloads
from daemon_lib.common import run_os_command
conn_api = None
cur_api = None
conn_dns = None
cur_dns = 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 PostgreSQL databases on localhost"
# Check the API database
try:
conn_api = connect(
host=self.this_node.name,
port=self.config["api_postgresql_port"],
dbname=self.config["api_postgresql_dbname"],
user=self.config["api_postgresql_user"],
password=self.config["api_postgresql_password"],
)
cur_api = conn_api.cursor()
cur_api.execute("""SELECT * FROM alembic_version""")
data = cur_api.fetchone()
except Exception as e:
health_delta = 50
err = str(e).split('\n')[0]
message = f"Failed to connect to PostgreSQL database {self.config['api_postgresql_dbname']}: {err}"
finally:
if cur_api is not None:
cur_api.close()
if conn_api is not None:
conn_api.close()
# Check for Patroni status
_, stdout, _ = run_os_command("patronictl --config-file /etc/patroni/config.yml list --format json")
patronictl_status = jloads(stdout)
this_node_patronictl_status = [p for p in patronictl_status if p["Member"] == self.this_node.name][0]
self.logger.out(f"{this_node_patronictl_status}, last node state: {self.last_coordinator_state}, current node state: {coordinator_state}", state="d")
# Invalid state, nothing returned; this is a fault
if health_delta == 0 and not this_node_patronictl_status:
health_delta = 10
message = "Unable to determine Patroni PostgreSQL node state"
# We want to check for a non-running Patroni, but not during or immediately after a coordinator
# transition. So we wait until 2 runs with the same coordinator state have been completed.
elif health_delta == 0 and self.last_coordinator_state == coordinator_state and this_node_patronictl_status["State"] != "running":
health_delta = 10
message = "Patroni PostgreSQL state is not running"
# Handle some exceptional cases
if health_delta > 0:
if coordinator_state in ["takeover", "relinquish"]:
# This scenario occurrs if this plugin run catches a node transitioning from primary to
# secondary coordinator. We can ignore it.
health_delta = 0
message = "Patroni PostgreSQL error reported but currently transitioning coordinator state; ignoring."
# 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)
# Update the last coordinator state
self.last_coordinator_state = coordinator_state
# 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