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feat: Coordinator request forwarding #1535

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15 changes: 7 additions & 8 deletions pages/clustering/high-availability/ha-commands-reference.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -14,12 +14,16 @@ Memgraph High Availability (HA) cluster.
## Cluster registration commands

<Callout type="warning">
**Important:** **All registration commands (adding coordinators and registering
data instances) must be executed on the *same* coordinator.** You may choose any
**Important:** You may choose any
coordinator for the initial setup; it automatically becomes the leader. After
setup, the choice no longer matters.
</Callout>

<Callout type="info">
All queries can be run on any coordinator. If currently the coordinator is not a leader, the query will be automatically forwarded to the current leader and executed there.
This is because Raft protocol specifies that only leader should accept changes in the cluster.
</Callout>

### `ADD COORDINATOR`

Adds a coordinator to the cluster.
Expand Down Expand Up @@ -78,7 +82,6 @@ REMOVE COORDINATOR coordinatorId;

{<h4 className="custom-header"> Behavior & implications </h4>}

- Must be executed on the **leader** coordinator.
- Leader coordinator **cannot** remove itself. To remove the leader, first
trigger a leadership change.

Expand Down Expand Up @@ -106,7 +109,6 @@ of each instance.

{<h4 className="custom-header"> Behavior & implications </h4>}

- Must be executed on the **leader** coordinator.
- Only bolt server can be updated.

{<h4 className="custom-header"> Example </h4>}
Expand Down Expand Up @@ -294,8 +296,7 @@ SHOW INSTANCE;

### `SHOW REPLICATION LAG`

Shows replication lag (in committed transactions) for all instances. Must be run
on the **leader**.
Shows replication lag (in committed transactions) for all instances.

```cypher
SHOW REPLICATION LAG;
Expand Down Expand Up @@ -326,7 +327,5 @@ FORCE RESET CLUSTER STATE;

{<h4 className="custom-header"> Implications </h4>}

- Must be executed on the **leader** coordinator.


<CommunityLinks/>
17 changes: 14 additions & 3 deletions pages/clustering/high-availability/how-high-availability-works.mdx
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Expand Up @@ -133,9 +133,20 @@ Below is a cleaned-up categorization.

#### Coordinator → Coordinator RPCs

| RPC | Purpose | Description |
| -------------------- | ------------------------------------------- | -------------------------------------------------------------------------------------------------------------------- |
| `ShowInstancesRpc` | Follower requests cluster state from leader | Sent by a follower coordinator to the leader coordinator when a user executes `SHOW INSTANCES` through the follower. |
| RPC | Purpose | Description |
| ------------------------ | -------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------- |
| `ShowInstancesRpc` | Follower requests cluster state from leader. | Sent by a follower coordinator to the leader coordinator when a user executes `SHOW INSTANCES` through the follower. |
| `AddCoordinatorRpc` | Follower requests adding coordinator. | Sent by a follower coordinator to the leader coordinator when a user executes `ADD COORDINATOR` through the follower. |
| `RemoveCoordinatorRpc` | Follower requests removing coordinator. | Sent by a follower coordinator to the leader coordinator when a user executes `REMOVE COORDINATOR` through the follower. |
| `RegisterInstanceRpc` | Follower requests registering an instance. | Sent by a follower coordinator to the leader coordinator when a user executes `REGISTER INSTANCE` through the follower. |
| `UnregisterInstanceRpc` | Follower requests unregistering an instance. | Sent by a follower coordinator to the leader coordinator when a user executes `UNREGISTER INSTANCE` through the follower. |
| `SetInstanceToMainRpc` | Follower requests updating main instance. | Sent by a follower coordinator to the leader coordinator when a user executes `SET INSTANCE TO MAIN` through the follower. |
| `DemoteInstanceRpc` | Follower requests demoting and instance. | Sent by a follower coordinator to the leader coordinator when a user executes `DEMOTE INSTANCE` through the follower. |
| `UpdateConfigRpc` | Follower requests updating config. | Sent by a follower coordinator to the leader coordinator when a user executes `UPDATE CONFIG` through the follower. |
| `ForceResetRpc` | Follower requests resetting cluster state. | Sent by a follower coordinator to the leader coordinator when a user executes `FORCE RESET` through the follower. |
| `ShowInstancesRpc` | Follower requests showing cluster state. | Sent by a follower coordinator to the leader coordinator when a user executes `SHOW INSTANCES` through the follower. |
| `GetRoutingTableRpc` | Follower requests a routing table. | Sent by a follower coordinator to the leader coordinator when a user connect using `bolt+routing` through the follower. |
| `CoordReplicationLagRpc` | Follower requests replication lag info. | Sent by a follower coordinator to the leader coordinator when a user executes `SHOW REPLICATION LAG` through the follower. |


#### Coordinator → Data Instance RPCs
Expand Down