mirror of https://github.com/hashicorp/consul
117 lines
5.0 KiB
Markdown
117 lines
5.0 KiB
Markdown
---
|
|
layout: docs
|
|
page_title: Upgrading Consul
|
|
sidebar_title: 'Upgrading'
|
|
sidebar_current: docs-upgrading-upgrading
|
|
description: >-
|
|
Consul is meant to be a long-running agent on any nodes participating in a
|
|
Consul cluster. These nodes consistently communicate with each other. As such,
|
|
protocol level compatibility and ease of upgrades is an important thing to
|
|
keep in mind when using Consul.
|
|
---
|
|
|
|
# Upgrading Consul
|
|
|
|
Consul is meant to be a long-running agent on any nodes participating in a
|
|
Consul cluster. These nodes consistently communicate with each other. As such,
|
|
protocol level compatibility and ease of upgrades is an important thing to
|
|
keep in mind when using Consul.
|
|
|
|
This page documents how to upgrade Consul when a new version is released.
|
|
|
|
## Standard Upgrades
|
|
|
|
For upgrades we strive to ensure backwards compatibility. To support this,
|
|
nodes gossip their protocol version and builds. This enables clients and
|
|
servers to intelligently enable new features when available, or to gracefully
|
|
fallback to a backward compatible mode of operation otherwise.
|
|
|
|
For most upgrades, the process is simple. Assuming the current version of
|
|
Consul is A, and version B is released.
|
|
|
|
1. Check the [version's upgrade notes](/docs/upgrade-specific.html) to ensure
|
|
there are no compatibility issues that will affect your workload. If there
|
|
are plan accordingly before continuing.
|
|
|
|
2. On each server, install version B of Consul.
|
|
|
|
3. One server at a time, shut down version A via `consul leave` and restart with version B. Wait until
|
|
the server is healthy and has rejoined the cluster before moving on to the
|
|
next server.
|
|
|
|
4. Once all the servers are upgraded, begin a rollout of clients following
|
|
the same process.
|
|
|
|
5. Done! You are now running the latest Consul agent. You can verify this
|
|
by running `consul members` to make sure all members have the latest
|
|
build and highest protocol version.
|
|
|
|
## Backward Incompatible Upgrades
|
|
|
|
In some cases, a backwards incompatible update may be released. This has not
|
|
been an issue yet, but to support upgrades we support setting an explicit
|
|
protocol version. This disables incompatible features and enables a 2-phase upgrade.
|
|
|
|
For the steps below, assume you're running version A of Consul, and then
|
|
version B comes out.
|
|
|
|
1. On each node, install version B of Consul.
|
|
|
|
2. One server at a time, shut down version A via `consul leave` and start version B with the
|
|
`-protocol=PREVIOUS` flag, where "PREVIOUS" is the protocol version of
|
|
version A (which can be discovered by running `consul -v` or `consul members`). Wait until the server is healthy and has rejoined the cluster
|
|
before moving on to the next server.
|
|
|
|
3. Once all nodes are running version B, go through every node and restart the
|
|
version B agent _without_ the `-protocol` flag, again wait for each server to
|
|
rejoin the cluster before continuing.
|
|
|
|
4. Done! You're now running the latest Consul agent speaking the latest protocol.
|
|
You can verify this is the case by running `consul members` to
|
|
make sure all members are speaking the same, latest protocol version.
|
|
|
|
The key to making this work is the [protocol compatibility](/docs/compatibility.html)
|
|
of Consul. The protocol version system is discussed below.
|
|
|
|
## Protocol Versions
|
|
|
|
By default, Consul agents speak the latest protocol they can. However, each
|
|
new version of Consul is also able to speak the previous protocol, if there
|
|
were any protocol changes.
|
|
|
|
You can see what protocol versions your version of Consul understands by
|
|
running `consul -v`. You'll see output similar to that below:
|
|
|
|
```shell
|
|
$ consul -v
|
|
Consul v0.7.0
|
|
Protocol 2 spoken by default, understands 2 to 3 (agent will automatically use protocol >2 when speaking to compatible agents)
|
|
```
|
|
|
|
This says the version of Consul as well as the protocol versions this
|
|
agent speaks and can understand.
|
|
|
|
Sometimes Consul will default to speak a lower protocol version
|
|
than it understands, in order to ease compatibility with older agents. For
|
|
example, Consul agents that understand version 3 claim to speak version 2,
|
|
and only send version 3 messages to agents that understand version 3. This
|
|
allows features to upshift automatically as agents are upgraded, and is the
|
|
strategy used whenever possible. If this is not possible, then you will need
|
|
to do a backward incompatible upgrade using the instructions above, and such
|
|
a requirement will be clearly outlined in the notes for a given release.
|
|
|
|
By specifying the `-protocol` flag on `consul agent`, you can tell the
|
|
Consul agent to speak any protocol version that it can understand. This
|
|
only specifies the protocol version to _speak_. Every Consul agent can
|
|
always understand the entire range of protocol versions it claims to
|
|
on `consul -v`.
|
|
|
|
~> **By running a previous protocol version**, some features
|
|
of Consul, especially newer features, may not be available. If this is the
|
|
case, Consul will typically warn you. In general, you should always upgrade
|
|
your cluster so that you can run the latest protocol version.
|
|
|
|
## Upgrading on Kubernetes
|
|
|
|
See the dedicated [Upgrading Consul on Kubernetes](/docs/platform/k8s/upgrading.html) page.
|