_mysql-diag.html.md.erb

This topic discusses how to use the `mysql-diag` tool in  MySQL for Pivotal Cloud Foundry (PCF).
`mysql-diag` prints the state of your MySQL highly available (HA) cluster and
suggests solutions if your node fails. Pivotal recommends running this tool against
your HA cluster before all deployments.

`mysql-diag` checks the following information about the status of your HA cluster:

- Membership status of all nodes
- Size as it appears to all nodes
- If it needs to be bootstrapped
- If replication is working
- Used disk space and inodes per server


## <a id='bosh-v2'></a>Run mysql-diag Using the BOSH Command Line Interface (CLI)

To use the BOSH CLI to run `mysql-diag`, do the following:

1. Obtain the information needed to use the BOSH CLI by doing the procedure in
[Gather Credential and IP Address Information](https://docs.pivotal.io/pivotalcf/customizing/trouble-advanced.html#gather).

1. SSH into your Ops Manager VM by doing the procedure in
[Log in to the Ops Manager VM with SSH](https://docs.pivotal.io/pivotalcf/customizing/trouble-advanced.html#ssh)
for your IaaS.

1. Log in to your BOSH Director by doing the procedure in
[Log in to the BOSH Director](https://docs.pivotal.io/pivotalcf/customizing/trouble-advanced.html#log-in).

1. Identify the VM to log in to with SSH by running the following command:

    ```
    bosh -e MY-ENV -d MY-DEPLOYMENT vms
    ```

    Where:
    + `MY-ENV` is the name of your environment.
    + `MY-DEPLOYMENT` is the name of your deployment.

1. Record the GUID associated with the `mysql-monitor` VM, also known as the jumpbox VM.

1. SSH into your `mysql-monitor` VM by running the following command:

    ```
    bosh -e MY-ENV -d MY-DEP ssh mysql-monitor/GUID
    ```

    Where:
    + `MY-ENV` is the name of your environment.
    + `MY-DEPLOYMENT` is the name of your deployment.
    + `GUID` is the GUID you recorded in the previous step.

1. View the status of your HA cluster by running the following command:

    ```
    mysql-diag
    ```


## <a id="healthy"></a> Example Healthy Output ##

The `mysql-diag` command returns the following message if your canary status is healthy:

<pre class="terminal">Checking canary status...healthy</pre>

Here is a sample `mysql-diag` output after the tool identified a healthy HA cluster:

<%= image_tag('mysql-diag-healthy-screen-shot.png') %>
<a href="images/mysql-diag-healthy-screen-shot.png" target="_blank">View a larger version of this image.</a>


## <a id="unhealthy"></a> Example Unhealthy Output ##

The `mysql-diag` command returns the following message if your canary status is unhealthy:

<pre class="terminal">Checking canary status...unhealthy</pre>

In the event of a broken HA cluster, running `mysql-diag` outputs actionable steps meant to expedite the recovery of that HA cluster. Below is a sample `mysql-diag` output after the tool identified an unhealthy HA cluster:

<%= image_tag('mysql-diag-unhealthy-screen-shot.png') %>
<a href="images/mysql-diag-unhealthy-screen-shot.png" target="_blank">View a larger version of this image.</a>