Temporal Worker K8s Operator

This is the Kubernetes Python Operator for the Temporal Worker.

Description

Temporal is a developer-first, open source platform that ensures the successful execution of services and applications (using workflows).

Use Workflow as Code (TM) to build and operate resilient applications. Leverage developer friendly primitives and avoid fighting your infrastructure

This operator provides a Temporal Worker, and consists of Python scripts which connect to a deployed Temporal server.

Usage

Deploying

To deploy the Charmed Temporal Worker, you can start by creating a Temporal workflow, or use the one provided in resource_sample_py. Once done, the project can be built as a ROCK and pushed to the local registry by running the following command inside the resource_sample_py directory:

make -C resource_sample_py build_rock

The Charmed Temporal Worker can then be deployed and connected to a deployed Temporal server using the Juju command line as follows:

juju deploy temporal-worker-k8s --resource temporal-worker-image=localhost:32000/temporal-worker-rock
juju config temporal-worker-k8s --file=path/to/config.yaml

config.yaml

temporal-worker-k8s:
  host: "localhost:7233" # Replace with Temporal server hostname
  queue: "test-queue"
  namespace: "test"

Once done, the charm should enter an active state, indicating that the worker is running successfully. To verify this, you can check the logs of the juju unit to ensure there are no errors with the workload container:

juju ssh --container temporal-worker temporal-worker-k8s/0 /charm/bin/pebble logs temporal-worker -f

Note: The only requirement for the ROCK is to have a scripts/start-worker.sh file, which will be used as the entry point for the charm to start the workload container.

Adding Secrets & Environment Variables

The Charmed Temporal Worker allows the user to configure multiple sources of environment variables and secrets to be injected into the workload container and consumed by the user's workflow definitions. These sources can be configured through the environment config parameter of the charm. Below are the three sources of environment variables and secrets currently supported. A user may choose to use one, all or none of them. Once the environment.yaml file is ready, it can be configured into the charm as follows:

juju config temporal-worker-k8s environment=@/path/to/environment.yaml

These environment variables can then be retrieved by the workflows by using the os package as follows:

import os
value1 = os.getenv("key1")

Direct Environment Variables

These are usually values that are not secret and can be stored as plaintext. An example is setting the application environment to staging or production. They can be set as follows:

environment.yaml

env:
  - name: key1
    value: value1
  - name: key2
    value: value2

Juju User Secrets (Requires Juju 3.3+)

Juju secrets are values which can be stored in the model and accessed by the charm. To do so, you must first add the secret and grant the charm access to it:

juju add-secret my-secret key1=value1 key2=value2

# Output: secret:<secret_id>

juju grant-secret my-secret temporal-worker-k8s

The environment variables can then be configured into the charm as follows:

environment.yaml

juju:
  - secret-id: <secret_id>
    name: env_var1
    key: key1
  - secret-id: <secret_id>
    name: env_var2
    key: key2

Vault

The Vault section below outlines how the Charmed Temporal Worker can be related to the Vault operator charm for storing secrets securely. Once done, the charm can be configured to fetch secrets from Vault and inject them as environment variables into the workload container. The secrets can be configured into the charm as follows:

environment.yaml

vault:
  - path: my-secrets
    name: env_var1
    key: key1
  - path: my-secrets
    name: env_var2
    key: key2

These secrets can then be added to Vault by running the following charm action:

juju run temporal-worker-k8s/leader add-vault-secret path="my-secrets" key="key1" value="value1"

Verifying

To verify that the setup is running correctly, run juju status --watch 2s and ensure the pod is active.

To run a basic workflow, you may use a simple client (e.g. sdk-python sample) and connect to the same Temporal server. If run on the same namespace and task queue as the Temporal Worker, it should be executed successfully.

Enable Proxy

To enable the Temporal worker charm to use an HTTP proxy, the following Juju model configurations can be set. The charm will read these values and set the HTTP_PROXY, HTTPS_PROXY and NO_PROXY environment in the workload container respectively.

juju model-config juju-http-proxy="<http_proxy>"
juju model-config juju-https-proxy="<https_proxy>"
juju model-config juju-no-proxy="<no_proxy>"

A config change may be needed if your charm is already deployed to force the charm to re-initialize.

Scaling

To add more replicas you can use the juju scale-application functionality i.e.

juju scale-application temporal-worker-k8s <num_of_replicas_required_replicas>

Error Monitoring

The Charmed Temporal Worker has a built-in Sentry interceptor which can be used to intercept and capture errors from the Temporal SDK. To enable it, run the following commands:

juju config temporal-worker-k8s sentry-dsn=<YOUR_SENTRY_DSN>
juju config temporal-worker-k8s sentry-release="1.0.0"
juju config temporal-worker-k8s sentry-environment="staging"

Observability

The Charmed Temporal Worker can be related to the Canonical Observability Stack in order to collect logs and telemetry. To deploy cos-lite and expose its endpoints as offers, follow these steps:

# Deploy the cos-lite bundle:
juju add-model cos
juju deploy cos-lite --trust

# Expose the cos integration endpoints:
juju offer prometheus:metrics-endpoint
juju offer loki:logging
juju offer grafana:grafana-dashboard

# Relate Temporal to the cos-lite apps:
juju relate temporal-worker-k8s admin/cos.grafana
juju relate temporal-worker-k8s admin/cos.loki
juju relate temporal-worker-k8s admin/cos.prometheus

# Access grafana with username "admin" and password:
juju run grafana/0 -m cos get-admin-password --wait 1m
# Grafana is listening on port 3000 of the app ip address.
# Dashboard can be accessed under "Temporal Worker SDK Metrics", make sure to select the juju model which contains your Charmed Temporal Worker.

Vault

The Charmed Temporal Worker can be related to the Vault operator charm to securely store credentials that can be accessed by workflows. This is the recommended way of storing workflow-related credentials in production environments. To enable this, run the following commands:

juju deploy vault-k8s --channel 1.16/edge

# After following Vault doc instructions to unseal Vault
juju relate temporal-worker-k8s vault-k8s

Note: The vault charm currently needs to be manually unsealed using the instructions found here.

For a reference on how to access credentials from Vault through the workflow code, activity2.py under the resource_sample directory shows a sample for writing and reading secrets in Vault.

Note: At the time of writing, the Vault operator charm currently has compatibility issues with some versions of Juju (e.g. Juju v3.2.4). It has been tested successfully with Juju v3.3.5.

PostgreSQL

The Charmed Temporal Worker can be related to the PostgreSQL operator charm to enable the creation of a database to be used by your workflows. To enable this, run the following commands:

juju deploy postgresql-k8s --channel 14/stable --trust
juju relate temporal-worker-k8s postgresql-k8s

Once this is done and all units are settled and active, you can refer to the database credentials within your workflow code using the following environment variables:

• TEMPORAL_DB_NAME
• TEMPORAL_DB_HOST
• TEMPORAL_DB_PORT
• TEMPORAL_DB_USER
• TEMPORAL_DB_PASSWORD
• TEMPORAL_DB_TLS

An example of this can be found in the db_activity.

Contributing

This charm is still in active development. Please see the Juju SDK docs for guidelines on enhancements to this charm following best practice guidelines, and CONTRIBUTING.md for developer guidance.