Name Resolving

This topic describes the name resolving capabilities of a9s LogMe for PCF.

Name Resolving

There are two ways to obtain the IP address for service instance DNS name:

  • Use the Consul cluster which comes with the installation of a9s Elasticsearch
  • Use the a9s BOSH DNS which can be installed on each Diego cell

Name Resolving with Consul

a9s Elasticsearch for PCF comes with its own highly available Consul cluster for service discovery and service failover procedures.

Consul is an HA service discovery and configuration tool, which includes features such as failure detection, an HA key/value store, and an HA DNS service that you can control through an HTTP-based REST interface.

To make use of this feature, talk to your company’s nameserver administrator to set up a delegation of a9s Elasticsearch hostnames. The hostnames of these queries end with a9s-elasticsearch-consul by default and must be delegated to the IP addresses of the Consul server within the a9s Elasticsearch tile. To figure out the IP addresses check the status tab of the tile and look for a9s Consul Cluster.

Status tab

For general information about Consul, see Consul by HashiCorp.

Name Resolving With a9s BOSH DNS Handler

The BOSH Director comes with a native DNS support. The DNS release provides a way to delegate certain domains via the handlers property to different DNS servers.

a9s Elasticsearch comes with the a9s BOSH DNS Handler. The release creates a file which is used by BOSH DNS to add an additional BOSH handler to the BOSH DNS configuration. See Additional Handlers. The file is stored here: /var/vcap/jobs/a9s-elasticsearch-bosh-dns-handler/dns/handlers.json. It follows the handlers_files_glob. The DNS Handler is only applied to the Diego cells where it is needed. It is applied through a runtime configuration. The tile must be deployed before the feature can be enabled, because it refers to an already installed a9s Elasticsearch for PCF tile.

  1. Import and stage a9s Elasticsearch for PCF as described above. Confirm that Enable BOSH DNS Handler is disabled.
  2. Apply the changes only for the a9s Elasticsearch for PCF tile.
  3. After the tile is deployed and the smoke-tests have run successfully, set Enable BOSH DNS Handler in the Management Cluster page to enabled.
  4. Redeploy only the (PAS)[] tile and the a9s Elasticsearch for PCF tile again.

If the installation was successful, an app deployed on PCF can resolve all a9s Elasticsearch instances with its DNS name.

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