SidekiqAlive

SidekiqAlive offers a solution to add liveness probe for a Sidekiq instance deployed in Kubernetes. This library can be used to check sidekiq health outside kubernetes.

How?

A http server is started and on each requests validates that a liveness key is stored in Redis. If it is there means is working.

A Sidekiq worker is the responsible to storing this key. If Sidekiq stops processing workers this key gets expired by Redis an consequently the http server will return a 500 error.

This worker is responsible to requeue itself for the next liveness probe.

Each instance in kubernetes will be checked based on ENV variable HOSTNAME (kubernetes sets this for each replica/pod).

On initialization SidekiqAlive will asign to Sidekiq::Worker a queue with the current host and add this queue to the current instance queues to process.

example:

hostname: foo
  Worker queue: sidekiq_alive-foo
  instance queues:
   - sidekiq_alive-foo
   *- your queues

hostname: bar
  Worker queue: sidekiq_alive-bar
  instance queues:
   - sidekiq_alive-bar
   *- your queues

Installation

Add this line to your application's Gemfile:

gem 'sidekiq_alive'

And then execute:

$ bundle

Or install it yourself as:

$ gem install sidekiq_alive

Usage

SidekiqAlive will start when running sidekiq command.

Run Sidekiq

bundle exec sidekiq

curl localhost:7433
#=> Alive!

how to disable? You can disabled by setting ENV variable DISABLE_SIDEKIQ_ALIVE example:

DISABLE_SIDEKIQ_ALIVE=true bundle exec sidekiq

Kubernetes setup

Set livenessProbe in your Kubernetes deployment

example with recommended setup:

Sidekiq < 6

spec:
  containers:
    - name: my_app
      image: my_app:latest
      env:
        - name: RAILS_ENV
          value: production
      command:
        - bundle
        - exec
        - sidekiq
      ports:
        - containerPort: 7433
      livenessProbe:
        httpGet:
          path: /
          port: 7433
        initialDelaySeconds: 80 # app specific. Time your sidekiq takes to start processing.
        timeoutSeconds: 5 # can be much less
      readinessProbe:
        httpGet:
          path: /
          port: 7433
        initialDelaySeconds: 80 # app specific
        timeoutSeconds: 5 # can be much less
      lifecycle:
        preStop:
          exec:
            # SIGTERM triggers a quick exit; gracefully terminate instead
            command: ['bundle', 'exec', 'sidekiqctl', 'quiet']
  terminationGracePeriodSeconds: 60 # put your longest Job time here plus security time.

Sidekiq >= 6

Create file:

kube/sidekiq_quiet

#!/bin/bash

# Find Pid
SIDEKIQ_PID=$(ps aux | grep sidekiq | grep busy | awk '{ print $2 }')
# Send TSTP signal
kill -SIGTSTP $SIDEKIQ_PID

Make it executable:

$ chmod +x kube/sidekiq_quiet

Execute it in your deployment preStop:

spec:
  containers:
    - name: my_app
      image: my_app:latest
      env:
        - name: RAILS_ENV
          value: production
      command:
        - bundle
        - exec
        - sidekiq
      ports:
        - containerPort: 7433
      livenessProbe:
        httpGet:
          path: /
          port: 7433
        initialDelaySeconds: 80 # app specific. Time your sidekiq takes to start processing.
        timeoutSeconds: 5 # can be much less
      readinessProbe:
        httpGet:
          path: /
          port: 7433
        initialDelaySeconds: 80 # app specific
        timeoutSeconds: 5 # can be much less
      lifecycle:
        preStop:
          exec:
            # SIGTERM triggers a quick exit; gracefully terminate instead
            command: ['kube/sidekiq_quiet']
  terminationGracePeriodSeconds: 60 # put your longest Job time here plus security time.

Outside kubernetes

It's just up to you how you want to use it.

An example in local would be:

bundle exec sidekiq
# let it initialize ...

curl localhost:7433
#=> Alive!

Options

SidekiqAlive.setup do |config|
  # ==> Server host
  # Host to bind the server.
  # Can also be set with the environment variable SIDEKIQ_ALIVE_HOST.
  # default: 0.0.0.0
  #
  #   config.host = 0.0.0.0

  # ==> Server port
  # Port to bind the server.
  # Can also be set with the environment variable SIDEKIQ_ALIVE_PORT.
  # default: 7433
  #
  #   config.port = 7433

  # ==> Server path
  # HTTP path to respond to.
  # Can also be set with the environment variable SIDEKIQ_ALIVE_PATH.
  # default: '/'
  #
  #   config.path = '/'

  # ==> Custom Liveness Probe
  # Extra check to decide if restart the pod or not for example connection to DB.
  # `false`, `nil` or `raise` will not write the liveness probe
  # default: proc { true }
  #
  #     config.custom_liveness_probe = proc { db_running? }

  # ==> Liveness key
  # Key to be stored in Redis as probe of liveness
  # default: "SIDEKIQ::LIVENESS_PROBE_TIMESTAMP"
  #
  #   config.liveness_key = "SIDEKIQ::LIVENESS_PROBE_TIMESTAMP"

  # ==> Time to live
  # Time for the key to be kept by Redis.
  # Here is where you can set de periodicity that the Sidekiq has to probe it is working
  # Time unit: seconds
  # default: 10 * 60 # 10 minutes
  #
  #   config.time_to_live = 10 * 60

  # ==> Callback
  # After the key is stored in redis you can perform anything.
  # For example a webhook or email to notify the team
  # default: proc {}
  #
  #    require 'net/http'
  #    config.callback = proc { Net::HTTP.get("https://status.com/ping") }

  # ==> Queue Prefix
  # SidekiqAlive will run in a independent queue for each instance/replica
  # This queue name will be generated with: "#{queue_prefix}-#{hostname}.
  # You can customize the prefix here.
  # default: :sidekiq_alive
  #
  #    config.queue_prefix = :other

  # ==> Rack server
  # Web server used to serve an HTTP response.
  # Can also be set with the environment variable SIDEKIQ_ALIVE_SERVER.
  # default: 'webrick'
  #
  #    config.server = 'puma'
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.

Here is an example rails app

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/arturictus/sidekiq_alive. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.