From 01c4876fb447b70106e934ad09cf9b921f33682a Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Fri, 6 May 2022 16:21:01 +0200
Subject: Specify remaining cluster-related endpoints

---
 doc/drafts/admin-api.md  | 79 ++++++++++++++++++++++++++++++++++++++++++++++--
 src/api/admin/cluster.rs |  2 ++
 2 files changed, 78 insertions(+), 3 deletions(-)

diff --git a/doc/drafts/admin-api.md b/doc/drafts/admin-api.md
index 1ba868ef..a518c93f 100644
--- a/doc/drafts/admin-api.md
+++ b/doc/drafts/admin-api.md
@@ -7,11 +7,15 @@ The admin API uses two different tokens for acces control, that are specified in
 
 # Administration API endpoints
 
-## Metrics `GET /metrics`
+## Metrics-related endpoints
+
+### Metrics `GET /metrics`
 
 Returns internal Garage metrics in Prometheus format.
 
-## GetClusterStatus `GET /status`
+## Cluster operations
+
+### GetClusterStatus `GET /status`
 
 Returns the cluster's current status in JSON, including:
 
@@ -50,6 +54,7 @@ Example response body:
     }
   },
   "layout": {
+    "version": 12,
     "roles": {
       "ec79480e0ce52ae26fd00c9da684e4fa56658d9c64cdcecb094e936de0bfe71f": {
         "zone": "dc1",
@@ -86,7 +91,7 @@ Example response body:
 }
 ```
 
-## GetClusterLayout `GET /layout`
+### GetClusterLayout `GET /layout`
 
 Returns the cluster's current layout in JSON, including:
 
@@ -99,6 +104,7 @@ Example response body:
 
 ```json
 {
+  "version": 12,
   "roles": {
     "ec79480e0ce52ae26fd00c9da684e4fa56658d9c64cdcecb094e936de0bfe71f": {
       "zone": "dc1",
@@ -133,3 +139,70 @@ Example response body:
   }
 }
 ```
+
+### UpdateClusterLayout `POST /layout`
+
+Send modifications to the cluster layout. These modifications will
+be included in the staged role changes, visible in subsequent calls
+of `GetClusterLayout`. Once the set of staged changes is satisfactory,
+the user may call `ApplyClusterLayout` to apply the changed changes,
+or `Revert ClusterLayout` to clear all of the staged changes in
+the layout.
+
+Request body format:
+
+```json
+{
+  <node_id>: {
+    "capacity": <new_capacity>,
+    "zone": <new_zone>,
+    "tags": [
+      <new_tag>,
+      ...
+    ]
+  },
+  <node_id_to_remove>: null,
+  ...
+}
+```
+
+Contrary to the CLI that may update only a subset of the fields
+`capacity`, `zone` and `tags`, when calling this API all of these
+values must be specified.
+
+
+### ApplyClusterLayout `POST /layout/apply`
+
+Applies to the cluster the layout changes currently registered as
+staged layout changes.
+
+Request body format:
+
+```json
+{
+  "version": 13
+}
+```
+
+Similarly to the CLI, the body must include the version of the new layout
+that will be created, which MUST be 1 + the value of the currently
+existing layout in the cluster.
+
+### RevertClusterLayout `POST /layout/revert`
+
+Clears all of the staged layout changes.
+
+Request body format:
+
+```json
+{
+  "version": 13
+}
+```
+
+Reverting the staged changes is done by incrementing the version number
+and clearing the contents of the staged change list.
+Similarly to the CLI, the body must include the incremented
+version number, which MUST be 1 + the value of the currently
+existing layout in the cluster.
+
diff --git a/src/api/admin/cluster.rs b/src/api/admin/cluster.rs
index f4835648..0eb754ac 100644
--- a/src/api/admin/cluster.rs
+++ b/src/api/admin/cluster.rs
@@ -52,6 +52,7 @@ fn get_cluster_layout(garage: &Arc<Garage>) -> GetClusterLayoutResponse {
 	let layout = garage.system.get_cluster_layout();
 
 	GetClusterLayoutResponse {
+		version: layout.version,
 		roles: layout
 			.roles
 			.items()
@@ -78,6 +79,7 @@ struct GetClusterStatusResponse {
 
 #[derive(Serialize)]
 struct GetClusterLayoutResponse {
+	version: u64,
 	roles: HashMap<String, Option<NodeRole>>,
 	#[serde(rename = "stagedRoleChanges")]
 	staged_role_changes: HashMap<String, Option<NodeRole>>,
-- 
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