emqx4.3/apps/emqx_ds_builtin_raft

emqx_ds_builtin_raft

Replication layer for the builtin EMQX durable storage backend that uses Raft algorithm.

Raft backend introduces the concept of site to alleviate the problem of changing node names. Site IDs are persistent, and they are randomly generated at the first startup of the node. Each node in the cluster has a unique site ID, that is independent from the Erlang node name (emqx@...).

Configurations

OTP application environment variables:

• emqx_durable_storage.reads: leader_preferred | local_preferred.

CLI

Runtime settings for the durable storages can be modified via CLI as well as the REST API. The following CLI commands are available:

• emqx ctl ds info — get a quick overview of the durable storage state
• emqx ctl ds set_replicas <DS> <Site1> <Site2> ... — update the list of replicas for a durable storage.
• emqx ctl ds join <DS> <Site> — add a replica of durable storage on the site
• emqx ctl ds leave <DS> <Site> — remove a replica of a durable storage from the site

HTTP APIs

The following REST APIs are available for managing the builtin durable storages:

• /ds/sites — list known sites.
• /ds/sites/:site — get information about the site (its status, current EMQX node name managing the site, etc.)
• /ds/storages — list durable storages
• /ds/storages/:ds — get information about the durable storage and its shards
• /ds/storages/:ds/replicas — list or update sites that contain replicas of a durable storage
• /ds/storages/:ds/replicas/:site — add or remove replica of the durable storage on the site