installers/charm/kafka-exporter/src/charm.py

#!/usr/bin/env python3
# Copyright 2021 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.
#
# For those usages not covered by the Apache License, Version 2.0 please
# contact: legal@canonical.com
#
# To get in touch with the maintainers, please contact:
# osm-charmers@lists.launchpad.net
##

# pylint: disable=E0213

from ipaddress import ip_network
import logging
from pathlib import Path
from typing import NoReturn, Optional
from urllib.parse import urlparse

from ops.main import main
from opslib.osm.charm import CharmedOsmBase, RelationsMissing
from opslib.osm.interfaces.grafana import GrafanaDashboardTarget
from opslib.osm.interfaces.kafka import KafkaClient
from opslib.osm.interfaces.prometheus import PrometheusScrapeTarget
from opslib.osm.pod import (
    ContainerV3Builder,
    IngressResourceV3Builder,
    PodSpecV3Builder,
)
from opslib.osm.validator import ModelValidator, validator


logger = logging.getLogger(__name__)

PORT = 9308


class ConfigModel(ModelValidator):
    site_url: Optional[str]
    cluster_issuer: Optional[str]
    ingress_class: Optional[str]
    ingress_whitelist_source_range: Optional[str]
    tls_secret_name: Optional[str]
    image_pull_policy: Optional[str]

    @validator("site_url")
    def validate_site_url(cls, v):
        if v:
            parsed = urlparse(v)
            if not parsed.scheme.startswith("http"):
                raise ValueError("value must start with http")
        return v

    @validator("ingress_whitelist_source_range")
    def validate_ingress_whitelist_source_range(cls, v):
        if v:
            ip_network(v)
        return v

    @validator("image_pull_policy")
    def validate_image_pull_policy(cls, v):
        values = {
            "always": "Always",
            "ifnotpresent": "IfNotPresent",
            "never": "Never",
        }
        v = v.lower()
        if v not in values.keys():
            raise ValueError("value must be always, ifnotpresent or never")
        return values[v]


class KafkaExporterCharm(CharmedOsmBase):
    def __init__(self, *args) -> NoReturn:
        super().__init__(*args, oci_image="image")

        # Provision Kafka relation to exchange information
        self.kafka_client = KafkaClient(self, "kafka")
        self.framework.observe(self.on["kafka"].relation_changed, self.configure_pod)
        self.framework.observe(self.on["kafka"].relation_broken, self.configure_pod)

        # Register relation to provide a Scraping Target
        self.scrape_target = PrometheusScrapeTarget(self, "prometheus-scrape")
        self.framework.observe(
            self.on["prometheus-scrape"].relation_joined, self._publish_scrape_info
        )

        # Register relation to provide a Dasboard Target
        self.dashboard_target = GrafanaDashboardTarget(self, "grafana-dashboard")
        self.framework.observe(
            self.on["grafana-dashboard"].relation_joined, self._publish_dashboard_info
        )

    def _publish_scrape_info(self, event) -> NoReturn:
        """Publishes scraping information for Prometheus.

        Args:
            event (EventBase): Prometheus relation event.
        """
        if self.unit.is_leader():
            hostname = (
                urlparse(self.model.config["site_url"]).hostname
                if self.model.config["site_url"]
                else self.model.app.name
            )
            port = str(PORT)
            if self.model.config.get("site_url", "").startswith("https://"):
                port = "443"
            elif self.model.config.get("site_url", "").startswith("http://"):
                port = "80"

            self.scrape_target.publish_info(
                hostname=hostname,
                port=port,
                metrics_path="/metrics",
                scrape_interval="30s",
                scrape_timeout="15s",
            )

    def _publish_dashboard_info(self, event) -> NoReturn:
        """Publish dashboards for Grafana.

        Args:
            event (EventBase): Grafana relation event.
        """
        if self.unit.is_leader():
            self.dashboard_target.publish_info(
                name="osm-kafka",
                dashboard=Path("templates/kafka_exporter_dashboard.json").read_text(),
            )

    def _check_missing_dependencies(self, config: ConfigModel):
        """Check if there is any relation missing.

        Args:
            config (ConfigModel): object with configuration information.

        Raises:
            RelationsMissing: if kafka is missing.
        """
        missing_relations = []

        if self.kafka_client.is_missing_data_in_unit():
            missing_relations.append("kafka")

        if missing_relations:
            raise RelationsMissing(missing_relations)

    def build_pod_spec(self, image_info):
        """Build the PodSpec to be used.

        Args:
            image_info (str): container image information.

        Returns:
            Dict: PodSpec information.
        """
        # Validate config
        config = ConfigModel(**dict(self.config))

        # Check relations
        self._check_missing_dependencies(config)

        # Create Builder for the PodSpec
        pod_spec_builder = PodSpecV3Builder()

        # Build container
        container_builder = ContainerV3Builder(
            self.app.name, image_info, config.image_pull_policy
        )
        container_builder.add_port(name=self.app.name, port=PORT)
        container_builder.add_http_readiness_probe(
            path="/api/health",
            port=PORT,
            initial_delay_seconds=10,
            period_seconds=10,
            timeout_seconds=5,
            success_threshold=1,
            failure_threshold=3,
        )
        container_builder.add_http_liveness_probe(
            path="/api/health",
            port=PORT,
            initial_delay_seconds=60,
            timeout_seconds=30,
            failure_threshold=10,
        )
        container_builder.add_command(
            [
                "kafka_exporter",
                f"--kafka.server={self.kafka_client.host}:{self.kafka_client.port}",
            ]
        )
        container = container_builder.build()

        # Add container to PodSpec
        pod_spec_builder.add_container(container)

        # Add ingress resources to PodSpec if site url exists
        if config.site_url:
            parsed = urlparse(config.site_url)
            annotations = {}
            if config.ingress_class:
                annotations["kubernetes.io/ingress.class"] = config.ingress_class
            ingress_resource_builder = IngressResourceV3Builder(
                f"{self.app.name}-ingress", annotations
            )

            if config.ingress_whitelist_source_range:
                annotations[
                    "nginx.ingress.kubernetes.io/whitelist-source-range"
                ] = config.ingress_whitelist_source_range

            if config.cluster_issuer:
                annotations["cert-manager.io/cluster-issuer"] = config.cluster_issuer

            if parsed.scheme == "https":
                ingress_resource_builder.add_tls(
                    [parsed.hostname], config.tls_secret_name
                )
            else:
                annotations["nginx.ingress.kubernetes.io/ssl-redirect"] = "false"

            ingress_resource_builder.add_rule(parsed.hostname, self.app.name, PORT)
            ingress_resource = ingress_resource_builder.build()
            pod_spec_builder.add_ingress_resource(ingress_resource)

        logger.debug(pod_spec_builder.build())

        return pod_spec_builder.build()


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