May 2017
Intermediate to advanced
436 pages
9h 44m
English
Content preview from The DevOps 2.1 Toolkit: Docker Swarm
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Scaling services
We should always run at least two instances of any given service. That way they can share the load and, if one of them fails, there will be no downtime. We'll explore Swarm's failover capability soon and leave load balancing for the next chapter.
We can, for example, tell Swarm that we want to run five replicas of then go-demo service:
docker service scale go-demo=5
With the service scale command, we scheduled five replicas. Swarm will make sure that five instances of go-demo are running somewhere inside the cluster.
We can confirm that, indeed, five replicas are running through the, already familiar, service ls command:
docker service ls
The output is as follows (IDs are removed for brevity):
NAME MODE REPLICAS IMAGE ...
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