docs(ds): Move Raft-related parts to emqx_ds_builtin_raft README

apps/emqx_ds_builtin_raft/README.md

@@ -1,3 +1,36 @@
 # `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

apps/emqx_durable_storage/README.md

@@ -13,11 +13,10 @@ This makes the storage disk requirements very predictable: only the number of _p
 
 DS _backend_ is a callback module that implements `emqx_ds` behavior.
 
-EMQX repository contains the "builtin" backend, implemented in `emqx_ds_replication_layer` module, that uses Raft algorithm for data replication, and RocksDB as the main storage.
+EMQX repository contains two builtin backends based on RocksDB:
 
-Note that builtin backend introduces the concept of **site** to alleviate the problem of changing node names.
+- `emqx_ds_builtin_local`
-Site IDs are persistent, and they are randomly generated at the first startup of the node.
+- `emqx_ds_builtin_raft`
-Each node in the cluster has a unique site ID, that is independent from the Erlang node name (`emqx@...`).
 
 ### Layout
 
@@ -113,8 +112,8 @@ In the future it can serve as a storage for retained messages or as a generic me
 
 # Configurations
 
-Global options for `emqx_durable_storage` application are configured via OTP application environment.
+Common global options for builtin backends are configured via OTP application environment.
-Database-specific settings are stored in the schema table.
+Database-specific settings are stored in EMQX config.
 
 The following application environment variables are available:
 
@@ -124,26 +123,9 @@ The following application environment variables are available:
 
 - `emqx_durable_storage.egress_flush_interval`: period at which the batches of messages are committed to the durable storage.
 
-- `emqx_durable_storage.reads`: `leader_preferred` | `local_preferred`.
-
-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:
+None
-
-- `/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
 
 # Other