Docker Swarm¶

Table of Contents¶

Getting started
1. Scaling a service
Private registry (no TLS)
1. Pushing an image to a private registry
OpenFaas (no TLS)
1. Viewing usage in Prometheus

Getting started¶

Docker swarm has the notion of managers and workers; nodes in the swarm cluster can be either, or both. The manager is used to delegate tasks and deploy services, whereas the workers will only do the work.

To create a swarm, use the command

docker swarm init

on the machine destined to be a manager. In the output of this command will be the join command, which should be executed on the worker nodes.

You can list the nodes and their status from the manager with

docker node ls

For more information on operating and maintaining swarms, see this section of the documentation.

Scaling a service¶

docker docs

Private registry (no TLS)¶

For more information, see the docker docs.

Deploy a registry as a service on a docker swarm with:

docker service create -p 5000:5000 -d --name registry registry:2

If deploying with OpenFaas, or similar, you may need to provide a network flag. In the case of OpenFaas, this is commonly

--network func_functions

Add the registry to your docker daemon configuration file with:

"insecure-registries":["192.168.1.150:5000"]

The configuration file is located either in

Linux: /etc/docker/daemon.json
OSX: ~/.docker/daemon.json

You may have to create this file. You can also access it through the docker dashboard, under the preferences section. After adding the registry, you must reload docker

Linux

sudo service docker reload

OSX

Use the docker icon in the application try to restart.

Pushing an image to a private registry¶

First, tag the image then push:

docker tag [image:tag] [registry]/[name:tag] && \
  docker push [registry]/[name:tag]

OpenFaas (no TLS)¶

Link to OpenFaas GitHub repositry.

To install and spawn OpenFaas, on a manager node use

git clone https://github.com/openfaas/faas && \
  cd faas && \
  ./deploy_stack.sh

OpenFaas, by default, will spawn a UI on port :8080, and will print out the login details during the above command (keep note, unless you change them).

You can install the OpenFaas CLI with either

curl -sSL https://cli.openfaas.com | sh

or on OSX:

brew install faas-cli

To prevent having to constantly supply the --gateway flag, we can set the environment variable

export OPENFAAS_URL=http://192.168.1.150:8080

The general approach with OpenFaas will be to create a function template using

faas-cli new hello-world --lang=python --prefix=192.168.1.150:5000

wherein you develop your function. Then we build and upload it to the repository:

faas-cli build -f hello-world.yml

and

faas-cli push -f hello-world.yml

Note that you can avoid having to supply -f *.yml by renaming the configuration file to stack.yml.

You can check the image is in the registry with

curl 192.168.1.150:5000/v2/hello-python/tags/list

Now we deploy the function

faas-cli deploy -f hello-world.yml

And invoke it with either

curl -X GET localhost:8080/function/hello-python

or using the invoke command of faas-cli.

Viewing usage in Prometheus¶

For example, to see the invocation total, adapt the link for your OpenFaas URL:

http://192.168.1.150:9090/graph?g0.range_input=2h&g0.stacked=1&g0.expr=rate(gateway_function_invocation_total%5B20s%5D)&g0.tab=0&g1.range_input=12h&g1.expr=gateway_service_count&g1.tab=0

notes

Docker Swarm

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