How to configure the use of the serial recursor and BOSH DNS settings using runtime config overrides

Products

• Operations Manager

Issue/Introduction

This article covers how to configure the use of the serial recursor selection strategy instead of the smart default setting. This setting is applied to all BOSH deployed VMs.

The Ops Manager UI exposes a few of the BOSH DNS configuration settings. Some unexposed settings can be modified via the Ops Manager API.

In DNS release 1.12, the recursor_selection property was added to allow operators to dictate how recursors are chosen. There are two strategies: smart and serial. Smart is the default strategy, which picks recursors randomly when doing a failover (pre-1.12 behavior). Serial is the strategy where recursors are picked in the order they are given, from /etc/resolv.conf or from the recursors property.

For more information, refer to Native DNS Support.

 

Environment

Product Version: 2.10

Resolution

1. Enable advance mode on Ops Manager. For more information, refer to How to Enable Advanced Mode in the Ops Manager - Curl.

2. Target the UAA on Ops Manager. For more information, refer to How to Enable Advanced Mode in the Ops Manager - UAAC.

3. Create an override configuration in vim.

For example, the following is an example named dns-runtime-config.json.
 

{
  "overrides": [
    {
      "runtime_config_name": "ops_manager_dns_runtime",
      "addon_name": "bosh-dns",
      "data": {
        "recursor_selection": "serial"
      }
    }
   ]
}

4. Run this command to issue the override:

uaac curl -X PUT https://<ops_man_url>/api/v0/staged/director/runtime_configs/overrides -d "$(cat dns-runtime-config.json)" -k

Verify the acceptance of the override by hitting this endpoint on the Ops Manager UI.

https://<ops_man_url>/api/v0/staged/director/runtime_configs/overrides

 

5. Apply Changes to the BOSH Director.

To verify the changes are successful, BOSH SSH to a BOSH deployed VM.

Examine the file, cat var/vcap/jobs/bosh-dns/config/config.json | jq. You should see "recursor_selection": "serial" for this VM.

For more information, refer to Provide a new list of runtime config overrides for the BOSH Director.