#!/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 pvcnoded.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.
        """

        pass

    def run(self):
        """
        run(): Perform the check actions and return a PluginResult object
        """

        # Run any imports first
        from psycopg2 import connect

        conn_metadata = None
        cur_metadata = 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 Metadata database (primary)
        try:
            conn_metadata = connect(
                host='127.0.0.1',
                port=self.config["metadata_postgresql_port"],
                dbname=self.config["metadata_postgresql_dbname"],
                user=self.config["metadata_postgresql_user"],
                password=self.config["metadata_postgresql_password"],
            )
            cur_metadata = conn_metadata.cursor()
            cur_metadata.execute("""SELECT * FROM alembic_version""")
            data = cur_metadata.fetchone()
        except Exception as e:
            health_delta = 50
            err = str(e).split('\n')[0]
            message = f"Failed to connect to PostgreSQL database {self.config['metadata_postgresql_dbname']}: {err}"
        finally:
            if cur_metadata is not None:
                cur_metadata.close()
            if conn_metadata is not None:
                conn_metadata.close()

        if health_delta == 0:
            # Check the PowerDNS database (secondary)
            try:
                conn_pdns = connect(
                    host='127.0.0.1',
                    port=self.config["pdns_postgresql_port"],
                    dbname=self.config["pdns_postgresql_dbname"],
                    user=self.config["pdns_postgresql_user"],
                    password=self.config["pdns_postgresql_password"],
                )
                cur_pdns = conn_pdns.cursor()
                cur_pdns.execute("""SELECT * FROM supermasters""")
                data = cur_pdns.fetchone()
            except Exception as e:
                health_delta = 50
                err = str(e).split('\n')[0]
                message = f"Failed to connect to PostgreSQL database {self.config['pdns_postgresql_dbname']}: {err}"
            finally:
                if cur_pdns is not None:
                    cur_pdns.close()
                if conn_pdns is not None:
                    conn_pdns.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