Enabling email notifications using Alertmanager on Kubernetes

Question

Pulumi · Accepted Answer

To enable email notifications using Alertmanager on Kubernetes, you will first need to deploy Alertmanager into your Kubernetes cluster and then configure it to send notifications via email when alerts are triggered. Here are the steps to do that, along with the Pulumi program written in TypeScript, which demonstrates how to set up such a notification system.

### Understanding the Resources and Configuration

1. **Kubernetes Deployment for Alertmanager**: This deploys the Alertmanager on your Kubernetes cluster. It will manage the alerts sent by a Prometheus server and trigger notifications when certain alert conditions are met.

2. **ConfigMap for Alertmanager Configuration**: Alertmanager requires a configuration file, which includes details about how notifications should be sent. For email notifications, you will need to specify the SMTP host, port, sender address, and receivers.

3. **Secret for AlertManager**: If your SMTP server requires authentication, you'll create a Kubernetes `Secret` with your SMTP credentials. This is a more secure way of storing sensitive information than putting it directly in the ConfigMap.

4. **Service to Expose Alertmanager**: If you want to access the Alertmanager UI, you can expose it via a Kubernetes `Service`.

Here is a basic Pulumi program that creates these resources for a typical Alertmanager setup that sends emails.

### The Pulumi Program

```typescript
import * as pulumi from "@pulumi/pulumi";
import * as k8s from "@pulumi/kubernetes";

const namespace = "monitoring"; // The namespace where Alertmanager will be deployed

// Configuration for the email notifier
const emailConfig = {
    smtpHost: "smtp.example.com",
    smtpPort: 587,
    smtpFrom: "alertmanager@example.com",
    smtpAuthUsername: "your-username",
    smtpAuthPassword: "your-password", // It's better to use Pulumi's config secrets for this
};

// Create a Kubernetes Secret for the Alertmanager email configuration
const alertmanagerSecret = new k8s.core.v1.Secret("alertmanager-smtp-secret", {
    metadata: {
        namespace: namespace,
    },
    stringData: {
        "smtp-auth-password": emailConfig.smtpAuthPassword,
    },
}, { provider: yourK8sProvider }); // Replace with your Kubernetes provider

// Create a ConfigMap for the Alertmanager configuration
const alertmanagerConfigMap = new k8s.core.v1.ConfigMap("alertmanager-config", {
    metadata: {
        namespace: namespace,
    },
    data: {
        "config.yml": `
global:
  resolve_timeout: 5m
  smtp_smarthost: '${emailConfig.smtpHost}:${emailConfig.smtpPort}'
  smtp_from: '${emailConfig.smtpFrom}'
  smtp_auth_username: '${emailConfig.smtpAuthUsername}'
  smtp_auth_password: '${alertmanagerSecret.metadata.apply(m => m.name)}'

route:
  receiver: 'email-notifications'
receivers:
- name: 'email-notifications'
  email_configs:
  - to: 'recipient@example.com'
`,
    },
}, { provider: yourK8sProvider }); // Replace with your Kubernetes provider

// Kubernetes Deployment for the Alertmanager
const alertmanagerDeployment = new k8s.apps.v1.Deployment("alertmanager", {
    metadata: {
        namespace: namespace,
    },
    spec: {
        replicas: 1,
        selector: {
            matchLabels: {
                app: "alertmanager",
            },
        },
        template: {
            metadata: {
                labels: {
                    app: "alertmanager",
                },
            },
            spec: {
                containers: [{
                    name: "alertmanager",
                    image: "quay.io/prometheus/alertmanager:v0.21.0",
                    args: [
                        "--config.file=/etc/alertmanager/config.yml",
                        "--storage.path=/alertmanager",
                    ],
                    ports: [{
                        name: "web",
                        containerPort: 9093,
                    }],
                    volumeMounts: [{
                        name: "config-volume",
                        mountPath: "/etc/alertmanager",
                    }],
                }],
                volumes: [{
                    name: "config-volume",
                    configMap: {
                        name: alertmanagerConfigMap.metadata.apply(m => m.name),
                    },
                }],
            },
        },
    },
}, { provider: yourK8sProvider }); // Replace with your Kubernetes provider

// Kubernetes Service to expose the Alertmanager UI and API
const alertmanagerService = new k8s.core.v1.Service("alertmanager", {
    metadata: {
        namespace: namespace,
    },
    spec: {
        type: "ClusterIP",
        ports: [{
            name: "web",
            port: 9093,
            targetPort: "web",
            protocol: "TCP",
        }],
        selector: {
            app: "alertmanager",
        },
    },
}, { provider: yourK8sProvider }); // Replace with your Kubernetes provider

export const alertmanagerServiceIP = alertmanagerService.spec.apply(s => s.clusterIP);
```

Replace `yourK8sProvider` with your Kubernetes provider configuration, and ensure that your SMTP credentials are secure, preferably using Pulumi's configuration secrets management for the `smtpAuthPassword` property.

### Exporting the Service IP Address

Notice that at the end of the program, we export `alertmanagerServiceIP`. This IP address can be used within your cluster to access the Alertmanager UI and API.

### Final Notes on Configuration

Remember, this is a basic setup and in a real-world scenario, you'd likely want more customization and potentially better credential management using Pulumi secrets. This program assumes you have a running Kubernetes cluster and have already set up a Pulumi provider for interacting with it.

To learn more about Pulumi and how to use it, please visit [Pulumi's documentation](https://www.pulumi.com/docs/). For details on Alertmanager and its configuration options, you might want to review [Alertmanager's documentation](https://prometheus.io/docs/alerting/latest/configuration/).