ยปGeneral Upgrade Process
Introduction
This document describes some best practices that you should follow when upgrading Consul. Some versions also have steps that are specific to that version, so make sure you also review the upgrade instructions for the version you are on.
Download the New Version
First, download the binary for the new version you want.
All current and past versions of the OSS and Enterprise releases are available here:
Prepare for the Upgrade
1. Take a snapshot:
You can inspect the snapshot to ensure if was successful with:
Example output:
This will ensure you have a safe fallback option in case something goes wrong. Store this snapshot somewhere safe. More documentation on snapshot usage is available here:
2. Temporarily modify your Consul configuration so that its log_level
is set to debug
. After doing this, issue the following command on your servers to
reload the configuration:
This change will give you more information to work with in the event something goes wrong.
Perform the Upgrade
1. Issue the following command to discover which server is currently the leader:
You should receive output similar to this (exact formatting and content may differ based on version):
Take note of which agent is the leader.
2. Copy the new consul
binary onto your servers and replace the existing
binary with the new one.
3. The following steps must be done in order on the server agents, leaving the leader agent for last. First force the server agent to leave the cluster with the following command:
Then, use a service management system (e.g., systemd, upstart, etc.) to restart the Consul service. If you are not using a service management system, you must restart the agent manually.
To validate that the agent has rejoined the cluster and is in sync with the leader, issue the following command:
Check whether the commit_index
and last_log_index
fields have the same value. If done properly,
this should avoid an unexpected leadership election due to loss of quorum.
4. Double-check that all servers are showing up in the cluster as expected and are on the correct version by issuing:
You should receive output similar to this:
Also double-check the raft state to make sure there is a leader and sufficient voters:
You should receive output similar to this:
5. Set your log_level
back to its original value and issue the following command
on your servers to reload the configuration:
Troubleshooting
Most problems with upgrading occur due to either failing to upgrade the leader agent last, or failing to wait for a follower agent to fully rejoin a cluster before moving on to another server. This can cause a loss of quorum and occasionally can result in all of your servers attempting to kick off leadership elections endlessly without ever reaching a quorum and electing a leader.
Most of these problems can be solved by following the steps outlined in our Outage Recovery document. If you are still having trouble after trying the recovery steps outlined there, then the following options for further assistance are available:
- OSS users without paid support plans can request help in our Community Forum
- Enterprise and OSS users with paid support plans can contact HashiCorp Support
When contacting Hashicorp Support, please include the following information in your ticket:
- Consul version you were upgrading FROM and TO.
- Debug level logs from all servers in the cluster that you are having trouble with. These should include logs from prior to the upgrade attempt up through the current time. If your logs were not set at debug level prior to the upgrade, please include those logs as well. Also, update your config to use debug logs, and include logs from after that was done.
- Your Consul config files (please redact any secrets).
- Output from
consul members -detailed
andconsul operator raft list-peers
from each server in your cluster.