2022-02-07 10:51:12 +00:00
|
|
|
+++
|
|
|
|
|
title = "Cluster layout management"
|
|
|
|
|
weight = 10
|
|
|
|
|
+++
|
2021-11-09 11:24:04 +00:00
|
|
|
|
|
|
|
|
The cluster layout in Garage is a table that assigns to each node a role in
|
|
|
|
|
the cluster. The role of a node in Garage can either be a storage node with
|
|
|
|
|
a certain capacity, or a gateway node that does not store data and is only
|
|
|
|
|
used as an API entry point for faster cluster access.
|
2022-02-07 10:51:12 +00:00
|
|
|
An introduction to building cluster layouts can be found in the [production deployment](@/documentation/cookbook/real-world.md) page.
|
2021-11-09 11:24:04 +00:00
|
|
|
|
|
|
|
|
## How cluster layouts work in Garage
|
|
|
|
|
|
|
|
|
|
In Garage, a cluster layout is composed of the following components:
|
|
|
|
|
|
|
|
|
|
- a table of roles assigned to nodes
|
|
|
|
|
- a version number
|
|
|
|
|
|
|
|
|
|
Garage nodes will always use the cluster layout with the highest version number.
|
|
|
|
|
|
|
|
|
|
Garage nodes also maintain and synchronize between them a set of proposed role
|
|
|
|
|
changes that haven't yet been applied. These changes will be applied (or
|
|
|
|
|
canceled) in the next version of the layout
|
|
|
|
|
|
|
|
|
|
The following commands insert modifications to the set of proposed role changes
|
|
|
|
|
for the next layout version (but they do not create the new layout immediately):
|
|
|
|
|
|
|
|
|
|
```bash
|
|
|
|
|
garage layout assign [...]
|
|
|
|
|
garage layout remove [...]
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
The following command can be used to inspect the layout that is currently set in the cluster
|
|
|
|
|
and the changes proposed for the next layout version, if any:
|
|
|
|
|
|
|
|
|
|
```bash
|
|
|
|
|
garage layout show
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
The following commands create a new layout with the specified version number,
|
|
|
|
|
that either takes into account the proposed changes or cancels them:
|
|
|
|
|
|
|
|
|
|
```bash
|
|
|
|
|
garage layout apply --version <new_version_number>
|
|
|
|
|
garage layout revert --version <new_version_number>
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
The version number of the new layout to create must be 1 + the version number
|
|
|
|
|
of the previous layout that existed in the cluster. The `apply` and `revert`
|
|
|
|
|
commands will fail otherwise.
|
|
|
|
|
|
|
|
|
|
## Warnings about Garage cluster layout management
|
|
|
|
|
|
|
|
|
|
**Warning: never make several calls to `garage layout apply` or `garage layout
|
|
|
|
|
revert` with the same value of the `--version` flag. Doing so can lead to the
|
|
|
|
|
creation of several different layouts with the same version number, in which
|
|
|
|
|
case your Garage cluster will become inconsistent until fixed.** If a call to
|
|
|
|
|
`garage layout apply` or `garage layout revert` has failed and `garage layout
|
|
|
|
|
show` indicates that a new layout with the given version number has not been
|
|
|
|
|
set in the cluster, then it is fine to call the command again with the same
|
|
|
|
|
version number.
|
|
|
|
|
|
|
|
|
|
If you are using the `garage` CLI by typing individual commands in your
|
|
|
|
|
shell, you shouldn't have much issues as long as you run commands one after
|
|
|
|
|
the other and take care of checking the output of `garage layout show`
|
|
|
|
|
before applying any changes.
|
|
|
|
|
|
|
|
|
|
If you are using the `garage` CLI to script layout changes, follow the following recommendations:
|
|
|
|
|
|
|
|
|
|
- Make all of your `garage` CLI calls to the same RPC host. Do not use the
|
|
|
|
|
`garage` CLI to connect to individual nodes to send them each a piece of the
|
|
|
|
|
layout changes you are making, as the changes propagate asynchronously
|
|
|
|
|
between nodes and might not all be taken into account at the time when the
|
|
|
|
|
new layout is applied.
|
|
|
|
|
|
|
|
|
|
- **Only call `garage layout apply` once**, and call it **strictly after** all
|
|
|
|
|
of the `layout assign` and `layout remove` commands have returned.
|
