Hologres:Multi-cluster and auto scaling (beta)

Verify auto scaling behavior

After enabling auto scaling, use pgbench (the native PostgreSQL performance testing tool) to confirm that scaling triggers correctly. This example uses a configuration of 32 CU per cluster, 1 reserved cluster, and a maximum of 4 clusters.

1. Create test tables and load data:

   CREATE TABLE tbl_1 (col1 INT, col2 INT, col3 TEXT);
   CREATE TABLE tbl_2 (col1 INT, col2 INT, col3 TEXT);
   INSERT INTO tbl_1 SELECT i, i+1, md5(random()::TEXT) FROM generate_series(0, 500000) AS i;
   INSERT INTO tbl_2 SELECT i, i+1, md5(random()::TEXT) FROM generate_series(0, 500000) AS i;

2. On the stress testing server, create a file named select.sql with the following query:

   EXPLAIN ANALYZE SELECT * FROM tbl_1 LEFT JOIN tbl_2 ON tbl_1.col3 = tbl_2.col3 ORDER BY 1;

3. Set the password as an environment variable:

   export PGPASSWORD='<AccessKey_Secret>'

4. Run the stress test. Replace the placeholders with your actual values. For connection parameter details, see Connect to Hologres.

   Placeholder	Description
   <AccessKey_Secret>	AccessKey secret for your account
   <Database>	Target Hologres database name
   <AccessKey_ID>	AccessKey ID for your account
   <Endpoint>	Hologres instance endpoint
   <Port>	Connection port

   pgbench \
     -c 30 \
     -j 30 \
     -f select.sql \
     -d <Database> \
     -U <AccessKey_ID> \
     -h <Endpoint> \
     -p <Port> \
     -T 1800

Expected results:

• Cluster CPU utilization:

  • When cluster 1 sustains high load, auto scaling adds a cluster (position 1 in the chart).

  • After the stress test ends, both clusters show low load and auto scaling removes the elastic cluster (position 2).

• Virtual warehouse CPU utilization:

  • A new cluster is added when the virtual warehouse CPU utilization continuously exceeds 85%.

  • After the new cluster is added, overall CPU utilization drops to approximately 70%.

Metrics

In the Hologres Console, monitor the following metrics for your virtual warehouse. For configuration instructions, see Metrics.

• Cluster CPU utilization

• Cluster memory usage

• Number of vCPUs launched by virtual warehouse auto scaling

Elastic event logs

1. On the Virtual Warehouse Management page, click the Elastic Event Execution Logs tab.

2. Select a time range to view past scaling events. Each event record includes the running time, virtual warehouse, execution status, event type, number of reserved clusters, and target number of clusters.

Cloud Monitor events

Auto scaling scale-out and scale-in events are recorded in CloudMonitor.

1. Go to the Cloud Monitor Event Center. On the System Event page, select Hologres as the product in the Event Monitoring area. The following auto scaling events are available:

   Event name	Description
   Instance:Warehouse:AutoElastic:Start	Auto scaling has started for a virtual warehouse
   Instance:Warehouse:AutoElastic:Finish	Auto scaling completed successfully
   Instance:Warehouse:AutoElastic:Failed	Auto scaling failed (for example, a Cluster could not be launched)

2. Based on these events, configure notifications or alert rules. For setup instructions, see Use alerts for system events.

The following shows an example Cloud Monitor event payload for a failed scale-out event:

{
    "status": "Failed",
    "instanceName": "<instance_id>",
    "resourceId": "<instance_resource_id>",
    "content": {
        "AutoElasticCPU": <cpu_num>,
        "ScaleType": "ScaleOut",
        "ScheduleId": "xxxxxx",
        "WarehouseId": "<warehouse_id>",
        "WarehouseName": "<warehouse_name>"
    },
    "product": "hologres",
    "time": 1722852008000,
    "level": "WARN",
    "regionId": "<region>",
    "id": "<event_id>",
    "groupId": "0",
    "name": "Instance:Warehouse:TimedElastic:Failed"
}

ActionTrail

All operations performed in the Hologres Console — including editing auto scaling configurations — and actual cluster scaling operations triggered by auto scaling are recorded in ActionTrail. For details, see Audit event logs.