SwarmKit is a toolkit for embedding orchestration and cluster management capabilities in your application.
Its main benefits are:
- Distributed: SwarmKit implements the Raft Consensus Algorithm in order to coordinate and does not rely on a single point of failure to perform decisions.
- Secure: Node communication and membership within a Swarm are secure out of the box. SwarmKit uses mutual TLS for node authentication, role authorization and transport encryption, automating both certificate issuance and rotation.
- Simple: SwarmKit is operationally simple and minimizes infrastructure dependendecies. It does not need an external database to operate.
Machines running SwarmKit can be grouped together in other to form a Swarm, coordinating tasks with each other. Once a machine joins, it becomes a Swarm Node. Nodes can either be Worker Nodes or Manager Nodes.
- Worker Nodes are responsible for running Tasks using an Executor. SwarmKit comes with a default Docker Container Executor that can be easily swapped out.
- Manager Nodes on the other hand accept specifications from the user and are responsible for reconciling the desired state with the actual cluster state.
An operator can dynamically update a Node's role by promoting a Worker to Manager or demoting a Manager to Worker.
Tasks are organized in Services. A service is a higher level abstraction that allows the user to declare the desired state of a group of tasks. Services define what type of task should be created as well as how to execute them (e.g. run this many instances at all times) and how to update them (e.g. rolling updates).
Requirements:
- go 1.6 or higher
- A working golang environment
From the project root directory, run:
make binaries
Before running tests for the first time, setup the tooling:
$ make setupThen run:
$ make allThese instructions assume that swarmd and swarmctl are in your PATH.
(Before starting, make sure /tmp/node-N don't exist)
Initialize the first node:
$ swarmd -d /tmp/node-1 --listen-control-api /tmp/node-1/control.sock --hostname node-1In two additional terminals, join two nodes (note: replace 127.0.0.1:4242 with the address of the first node)
$ swarmd -d /tmp/node-2 --hostname node-2 --join-addr 127.0.0.1:4242
$ swarmd -d /tmp/node-3 --hostname node-3 --join-addr 127.0.0.1:4242In a fourth terminal, use swarmctl to explore and control the cluster. Before
running swarmctl, set the SWARM_SOCKET environment variable to the path to the
manager socket that was specified to --listen-control-api when starting the
manager.
To list nodes:
$ export SWARM_SOCKET=/tmp/manager1/swarm.sock
$ swarmctl node ls
ID Name Status Availability
87pn3pug404xs4x86b5nwlwbr node-1 READY ACTIVE
by2ihzjyg9m674j3cjdit3reo node-2 READY ACTIVE
87pn3pug404xs4x86b5nwlwbr node-3 READY ACTIVE
Create and manage a service
Start a 'redis' service:
$ swarmctl service create --name redis --image redis
List the running services:
ID Name Image Instances
-- ---- ----- ---------
enf3gkwlnmasgurdyebp555ja redis redis 1
Inspect the service:
$ swarmctl service inspect ping
ID : enf3gkwlnmasgurdyebp555ja
Name : redis
Instances : 1
Template
Container
Image : redis
Task ID Service Instance Image Desired State Last State Node
------- ------- -------- ----- ------------- ---------- ----
8oobrcr5u9lofmcbg7goaluyw redis 1 redis RUNNING RUNNING 1 minute ago node-1
Now change the instance count:
$ swarmctl service update redis --instances 4
enf3gkwlnmasgurdyebp555ja
$
$ swarmctl service inspect ping
ID : enf3gkwlnmasgurdyebp555ja
Name : redis
Instances : 4
Template
Container
Image : redis
Task ID Service Instance Image Desired State Last State Node
------- ------- -------- ----- ------------- ---------- ----
8oobrcr5u9lofmcbg7goaluyw redis 1 redis RUNNING RUNNING 2 minutes ago node-1
cdv2oca2zc5upft24494orn1v redis 2 redis RUNNING RUNNING 6 seconds ago node-2
0x7e6a1d74nrwgcbbk9c12cqo redis 3 redis RUNNING RUNNING 6 seconds ago node-2
1c8zxfj0eifhbdxrgforqz4dp redis 4 redis RUNNING RUNNING 6 seconds ago node-1