Monitoring the MySQL Service

Warning: MySQL for PCF v1.10 is no longer supported because it has reached the End of General Support (EOGS) phase as defined by the Support Lifecycle Policy. To stay up to date with the latest software and security updates, upgrade to a supported version.

This document describes the metrics that are produced by MySQL for PCF, and everything you need to know about the Replication Canary. For information about the Interruptor, see Using the Interruptor.

Metrics

MySQL emits metrics that can be used to monitor the health and performance of the MySQL deployment. The Loggregator Firehose exposes these metrics.

The metrics polling interval defaults to 30 seconds. You can change this interval by navigating to the Advanced Options configuration pane and entering a new value in Metrics polling interval (min: 10).

Third-party monitoring tools can consume MySQL for PCF’s metrics using an nozzle to monitor MySQL performance and health. For more information, see this section on nozzles. For an example Datadog configuration that displays some of the significant metrics outlined below, see the CF Redis and MySQL example dashboards. Pivotal does not endorse or provide support for any third party solution.

Key Performance Indicators

Key Performance Indicators (KPIs) for MySQL for PCF are metrics that operators find most useful for monitoring their MySQL service to ensure smooth operation. KPIs are high-signal-value metrics that can indicate emerging issues. KPIs can be raw component metrics or derived metrics generated by applying formulas to raw metrics.

Pivotal provides the following KPIs as general alerting and response guidance for typical MySQL for PCF installations. Pivotal recommends that operators continue to fine-tune the alert measures to their installation by observing historical trends. Pivotal also recommends that operators expand beyond this guidance and create new, installation-specific monitoring metrics, thresholds, and alerts based on learning from their own installations.

MySQL for PCF KPIs

This section lists the KPIs that are specific for MySQL for PCF.

For a list of general KPIs that apply to all instances, and not specifically to MySQL for PCF, see BOSH Health Metrics.

For a list of all MySQL for PCF component metrics, see All MySQL Metrics.

Server Availability

Galera WSREP Ready

Galera WSREP Cluster Size

Galera WSREP Cluster Status

Persistent and Ephemeral Disk Used

Service Plans Allocated

Connections

Questions

BOSH Health Metrics

All BOSH-deployed components generate the following component metrics; these component metrics also serve as KPIs for the MySQL for PCF service.

RAM

CPU

Persistent Disk

MySQL-Specific Metrics

Galera-Specific Metrics

For more information on monitoring PCF, see Monitoring Pivotal Cloud Foundry.

Replication Canary

MySQL for Pivotal Cloud Foundry (PCF) is a clustered solution that uses replication to provide benefits such as quick failover and rolling upgrades. This is more complex than a single node system with no replication. MySQL for PCF includes a Replication Canary to help with the increased complexity. The Replication Canary is a long-running monitor that validates that replication is working within the MySQL cluster.

How it Works

The Replication Canary writes to a private dataset in the cluster, and attempts to read that data from each node. It pauses between writing and reading to ensure that the writesets have been committed across each node of the cluster. The private dataset does not use a significant amount of disk capacity.

When replication fails to work properly, the Canary detects that it cannot read the data from all nodes, and immediately takes two actions:

• Emails a pre-configured address with a message that replication has failed. See the sample below.
• Disables client access to the cluster.

Note: Malfunctioning replication exposes the cluster to the possibility of data loss. Because of this, both behaviors are enabled by default. It is critical that you contact Pivotal support immediately in the case of replication failure. Support will work with you to determine the nature of the cluster failure and provide guidance regarding a solution.

Sample Notification Email

If the Canary detects a replication failure, it immediately sends an email through the Pivotal Application Service (PAS) or Elastic Runtime notification service. See the following example:

Subject: CF Notification: p-mysql Replication Canary, alert 417

This message was sent directly to your email address.

{alert-code 417}
This is an email to notify you that the MySQL service's replication canary has detected an unsafe cluster condition in which replication is not performing as expected across all nodes.

Cluster Access

Each time the Canary detects cluster replication failure, it instructs all proxies to disable connections to the database cluster. If the replication issue resolves, the Canary detects this and automatically restores client access to the cluster.

If you must restore access to the cluster regardless of the Replication Canary, contact Support.

Determine Proxy State

You can determine if the Canary disabled cluster access by using the Proxy API. See the following example:

ubuntu@ip-10-0-0-38:~$ curl -ku admin:PASSWORD_FROM_OPSMGR -X GET https://proxy-api-p-mysql.SYSTEM-DOMAIN/v0/cluster ; echo
{"currentBackendIndex":0,"trafficEnabled":false,"message":"Disabling cluster traffic","lastUpdated":"2016-07-27T05:16:29.197754077Z"}

Enable the Replication Canary

To enable the Replication Canary, follow the instructions below to configure both the PAS or Elastic Runtime tile and the MySQL for PCF tile.

Configure the PAS or Elastic Runtime Tile

Note: In a typical PCF deployment, these settings are already configured.

1. In the SMTP Config section, enter a From Email that the Replication Canary can use to send notifications, along with the SMTP server configuration.
2. In the Errands section, select the Notifications errand.

Configure the MySQL for PCF Tile

1. In the Advanced Options section, select Enable replication canary.
2. If you want to the Replication Canary to send email but not disable access at the proxy, select Notify only.

   Note: Pivotal recommends leaving this checkbox unselected due to the possibility of data loss from replication failure.

3. You can override the Replication canary time period. The Replication canary time period sets how frequently the canary checks for replication failure, in seconds. This adds a small amount of load to the databases, but the canary reacts more quickly to replication failure. The default is 30 seconds.

   

4. You can override the Replication canary read delay. The Replication canary read delay sets how long the canary waits to verify data is replicating across each MySQL node, in seconds. Clusters under heavy load experience some small replication lag as writesets are committed across the nodes. The Default is 20 seconds.

5. Enter an Email address to receive monitoring notifications. Use a closely monitored email address account. The purpose of the Canary is to escalate replication failure as quickly as possible.

6. In the Resource Config section, ensure the Monitoring job has one instance.

Disable the Replication Canary

If you do not need the Replication Canary, for instance if you use a single MySQL node, follow this procedure to disable both the job and the resource configuration.

1. In the Advanced Options section of the MySQL for PCF tile, select Disable Replication Canary.

2. In the Resource Config pane, set the Monitoring job to zero instances.