etcd

etcd resources represent a distributed key-value store, commonly used to hold cluster state and configuration. Plakar Control Plane connects to a node of the cluster and captures a snapshot of the whole key-value store. etcd integration supports multiple protocols.

All etcd protocols are backup only. A snapshot is captured into a Kloset store, but Plakar Control Plane never writes back to a cluster, so etcd resources have no destination app. See Recovering a cluster for how a snapshot is put back into service.

Inventory Management

No managed inventory can discover etcd clusters, so you need to set up a self-managed inventory and add the resource manually.

Adding etcd as a resource

Register the resource with no class or subclass. For the endpoint, use the hostname of a node in the cluster with its port. See resources documentation for more information on how to set up resources on a self-managed inventory.

1. etcd protocol

The etcd protocol connects to the cluster over plain HTTP. It is the default form and behaves the same as etcd+http.

Backup flow

A backup captures a single file, dump, produced by the etcd snapshot API. It holds the entire key-value store as of the moment the snapshot was taken, and is the format etcdutl expects during recovery.

flowchart TD
  subgraph Cluster["etcd Cluster"]
    Node["Cluster node"]
  end

  subgraph Plakar["Plakar Control Plane"]
    Source["etcd
Source app"]
    Backup["Backup process
Encrypt & deduplicate"]
  end

  Store["Kloset Store"]

  Source -->|"snapshot request over HTTP"| Node
  Node -->|"dump"| Backup
  Backup --> Store

Source configuration

The following settings are available when configuring a source app using the etcd protocol.

  • Endpoints: Comma-separated list of node endpoints to connect to. Takes priority over the endpoint registered on the resource, which lets a backup reach several nodes of the same cluster rather than depending on a single one.
  • Password: The password used to authenticate with the cluster.
  • Username: The username used to authenticate with the cluster.

2. etcd+http protocol

The etcd+http protocol connects to the cluster over plain HTTP, stated explicitly rather than relying on the default.

Backup flow

A backup captures a single file, dump, produced by the etcd snapshot API. It holds the entire key-value store as of the moment the snapshot was taken, and is the format etcdutl expects during recovery.

flowchart TD
  subgraph Cluster["etcd Cluster"]
    Node["Cluster node"]
  end

  subgraph Plakar["Plakar Control Plane"]
    Source["etcd
Source app"]
    Backup["Backup process
Encrypt & deduplicate"]
  end

  Store["Kloset Store"]

  Source -->|"snapshot request over HTTP"| Node
  Node -->|"dump"| Backup
  Backup --> Store

Source configuration

The following settings are available when configuring a source app using the etcd+http protocol.

  • Endpoints: Comma-separated list of node endpoints to connect to. Takes priority over the endpoint registered on the resource, which lets a backup reach several nodes of the same cluster rather than depending on a single one.
  • Password: The password used to authenticate with the cluster.
  • Username: The username used to authenticate with the cluster.

3. etcd+https protocol

The etcd+https protocol connects to the cluster over TLS. Use it whenever the cluster is reached over an untrusted network, so credentials and cluster state are not transmitted in clear text.

Backup flow

A backup captures a single file, dump, produced by the etcd snapshot API. It holds the entire key-value store as of the moment the snapshot was taken, and is the format etcdutl expects during recovery.

flowchart TD
  subgraph Cluster["etcd Cluster"]
    Node["Cluster node"]
  end

  subgraph Plakar["Plakar Control Plane"]
    Source["etcd
Source app"]
    Backup["Backup process
Encrypt & deduplicate"]
  end

  Store["Kloset Store"]

  Source -->|"snapshot request over TLS"| Node
  Node -->|"dump"| Backup
  Backup --> Store

Source configuration

The following settings are available when configuring a source app using the etcd+https protocol.

  • Endpoints: Comma-separated list of node endpoints to connect to. Takes priority over the endpoint registered on the resource, which lets a backup reach several nodes of the same cluster rather than depending on a single one.
  • Password: The password used to authenticate with the cluster.
  • Username: The username used to authenticate with the cluster.

Recovering a cluster

etcd does not expose a way to restore a snapshot through its API, so Plakar Control Plane cannot write one back into a running cluster. Recovery is a two-step process: restore the dump file from the snapshot to disk, then use etcdutl to provision a new etcd data directory from it.

See the etcd disaster recovery documentation for the upstream procedure.

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