installers/charm/pla/src/charm.py

#!/usr/bin/env python3
#   Copyright 2020 Canonical Ltd.
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

from glob import glob
import logging
from pathlib import Path
from string import Template
import sys

from ops.charm import CharmBase
from ops.framework import StoredState, Object
from ops.main import main
from ops.model import (
    ActiveStatus,
    MaintenanceStatus,
    WaitingStatus,
)


sys.path.append("lib")


logger = logging.getLogger(__name__)


class PLACharm(CharmBase):
    state = StoredState()

    def __init__(self, framework, key):
        super().__init__(framework, key)
        self.state.set_default(spec=None)
        self.state.set_default(kafka_host=None)
        self.state.set_default(kafka_port=None)
        self.state.set_default(mongodb_uri=None)

        # Observe Charm related events
        self.framework.observe(self.on.config_changed, self.on_config_changed)
        self.framework.observe(self.on.start, self.on_start)
        self.framework.observe(self.on.upgrade_charm, self.on_upgrade_charm)

        # Relations
        self.framework.observe(
            self.on.kafka_relation_changed, self.on_kafka_relation_changed
        )
        self.framework.observe(
            self.on.mongo_relation_changed, self.on_mongo_relation_changed
        )

    def _apply_spec(self):
        # Only apply the spec if this unit is a leader.
        unit = self.model.unit
        if not unit.is_leader():
            unit.status = ActiveStatus("ready")
            return
        if not self.state.kafka_host or not self.state.kafka_port:
            unit.status = WaitingStatus("Waiting for Kafka")
            return
        if not self.state.mongodb_uri:
            unit.status = WaitingStatus("Waiting for MongoDB")
            return

        unit.status = MaintenanceStatus("Applying new pod spec")

        new_spec = self.make_pod_spec()
        if new_spec == self.state.spec:
            unit.status = ActiveStatus("ready")
            return
        self.framework.model.pod.set_spec(new_spec)
        self.state.spec = new_spec
        unit.status = ActiveStatus("ready")

    def make_pod_spec(self):
        config = self.framework.model.config

        ports = [
            {"name": "port", "containerPort": config["port"], "protocol": "TCP", },
        ]

        config_spec = {
            "OSMPLA_MESSAGE_DRIVER": "kafka",
            "OSMPLA_MESSAGE_HOST": self.state.kafka_host,
            "OSMPLA_MESSAGE_PORT": self.state.kafka_port,
            "OSMPLA_DATABASE_DRIVER": "mongo",
            "OSMPLA_DATABASE_URI": self.state.mongodb_uri,
            "OSMPLA_GLOBAL_LOG_LEVEL": config["log_level"],
            "OSMPLA_DATABASE_COMMONKEY": config["database_common_key"],
        }

        spec = {
            "version": 2,
            "containers": [
                {
                    "name": self.framework.model.app.name,
                    "image": config["image"],
                    "ports": ports,
                    "config": config_spec,
                }
            ],
        }

        return spec

    def on_config_changed(self, event):
        """Handle changes in configuration"""
        self._apply_spec()

    def on_start(self, event):
        """Called when the charm is being installed"""
        self._apply_spec()

    def on_upgrade_charm(self, event):
        """Upgrade the charm."""
        unit = self.model.unit
        unit.status = MaintenanceStatus("Upgrading charm")
        self._apply_spec()

    def on_kafka_relation_changed(self, event):
        kafka_host = event.relation.data[event.unit].get("host")
        kafka_port = event.relation.data[event.unit].get("port")
        if kafka_host and self.state.kafka_host != kafka_host:
            self.state.kafka_host = kafka_host
        if kafka_port and self.state.kafka_port != kafka_port:
            self.state.kafka_port = kafka_port
        self._apply_spec()

    def on_mongo_relation_changed(self, event):
        mongodb_uri = event.relation.data[event.unit].get(
            "connection_string"
        )
        if mongodb_uri and self.state.mongodb_uri != mongodb_uri:
            self.state.mongodb_uri = mongodb_uri
        self._apply_spec()


if __name__ == "__main__":
    main(PLACharm)