Physical Cluster Replication Monitoring

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You can monitor a physical cluster replication (PCR) stream using:

• SHOW VIRTUAL CLUSTER ... WITH REPLICATION STATUS in the SQL shell.
• The Physical Cluster Replication dashboard on the DB Console.
• Prometheus and Alertmanager to track and alert on replication metrics.

When you complete a failover, there will be a gap in the primary cluster's metrics whether you are monitoring via the DB Console or Prometheus.

The standby cluster will also require separate monitoring to ensure observability during the failover period. You can use the DB console to track the relevant metrics, or you can use a tool like Grafana to create two separate dashboards, one for each cluster, or a single dashboard with data from both clusters.

SQL Shell

In the standby cluster's SQL shell, you can query SHOW VIRTUAL CLUSTER ... WITH REPLICATION STATUS for detail on status and timestamps for planning failover:

SHOW VIRTUAL CLUSTER main WITH REPLICATION STATUS;

Refer to Responses for a description of each field.

id | name | source_tenant_name |              source_cluster_uri                 |         retained_time         |    replicated_time           | replication_lag | failover_time                   |   status
---+------+--------------------+-------------------------------------------------+-------------------------------+------------------------------+-----------------+--------------------------------+--------------
3  | main | main               | postgresql://user@hostname or IP:26257?redacted | 2023-09-28 16:09:04.327473+00 | 2023-09-28 17:41:18.03092+00 | 00:00:19.602682 | 1695922878030920020.0000000000 | replicating
(1 row)

Responses

Data state

DB Console

You can use the Physical Cluster Replication dashboard of the standby cluster's DB Console to monitor:

• Logical bytes
• SST bytes
• Replication Lag

Prometheus

You can use Prometheus and Alertmanager to track and alert on PCR metrics. Refer to the Monitor CockroachDB with Prometheus tutorial for steps to set up Prometheus.

We recommend tracking the following metrics:

• physical_replication.logical_bytes: The logical bytes (the sum of all keys and values) ingested by all PCR jobs.
• physical_replication.sst_bytes: The SST bytes (compressed) sent to the KV layer by all PCR jobs.
• physical_replication.replicated_time_seconds: The replicated time of the physical replication stream in seconds since the Unix epoch.

Data verification

To verify that the data at a certain point in time is correct on the standby cluster, you can use the current replicated time from the replication job information to run a point-in-time fingerprint on both the primary and standby clusters. This will verify that the transmission and ingestion of the data on the standby cluster, at that point in time, is correct.

1. Retrieve the current replicated time of the replication job on the standby cluster with SHOW VIRTUAL CLUSTER:

   SELECT replicated_time FROM [SHOW VIRTUAL CLUSTER standbymain WITH REPLICATION STATUS];
   

        replicated_time
   ----------------------------
   2024-01-09 16:15:45.291575+00
   (1 row)
   

   For detail on connecting to the standby cluster, refer to Set Up Physical Cluster Replication.

2. From the primary cluster's system virtual cluster, specify a timestamp at or earlier than the current replicated_time to retrieve the fingerprint. This example uses the current replicated_time:

   SELECT * FROM [SHOW EXPERIMENTAL_FINGERPRINTS FROM VIRTUAL CLUSTER main] AS OF SYSTEM TIME '2024-01-09 16:15:45.291575+00';
   

   tenant_name |             end_ts             |     fingerprint
   ------------+--------------------------------+----------------------
   main        | 1704816945291575000.0000000000 | 2646132238164576487
   (1 row)
   

   For detail on connecting to the primary cluster, refer to Set Up Physical Cluster Replication.

3. From the standby cluster's system virtual cluster, specify the same timestamp used on the primary cluster to retrieve the standby cluster's fingerprint:

   SELECT * FROM [SHOW EXPERIMENTAL_FINGERPRINTS FROM VIRTUAL CLUSTER standbymain] AS OF SYSTEM TIME '2024-01-09 16:15:45.291575+00';
   

       tenant_name     |             end_ts             |     fingerprint
   --------------------+--------------------------------+----------------------
   standbymain         | 1704816945291575000.0000000000 | 2646132238164576487
   (1 row)
   

4. Compare the fingerprints of the primary and standby clusters to verify the data. The same value for the fingerprints indicates the data is correct.

See also

• DB Console Overview
• Monitoring and Alerting
• Physical Cluster Replication Overview
• Cluster Virtualization Overview

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