Defining DNS Observer jobs

The DNS Observer is installed as part of the core installation procedure. Using the DNS Observer, you can query internal DNS server performance, and use the returned information on response times and service addresses to create topologies within the topology service. The DNS Observer supports forward and reverse lookup calls, with recurse or no recurse options.

Before you begin

Ensure you have the DNS access details to hand, such as domain, DNS server address and port number.

Remember: Swagger documentation for the observer is available at the following default location: https://<your host>/1.0/dns-observer/swagger

About this task

The DNS Observer (nasm-dns-observer) provides DNS query services and topological insight into how a specified DNS server is performing forward (name-to-IP address) or reverse (IP address-to-name) lookups. Query results include a list of addresses, information on how long it takes the DNS server to resolve a lookup, and, optionally (with the maximum number of recursive calls set at 200) how the DNS server is recursively resolving a given name or IP address.

Job data is automatically posted to the topology service, after which the job status expires, after a set amount of time. The Topology Viewer displays the results with color-coded lines representing the relationships between resources, and the lookup time in ms. A tabular view of the relationship details is also available.

Tip: The relationship types can be customized with line color, width and pattern functions. See the Creating custom relationship type styles topic for more information.

dns_observer_common.sh: The configuration file you use to customize DNS Observer settings.; The parameters defined here are then used by the DNS forward and reverse lookup scripts (dns_observer_forward_lookup_start.sh and dns_observer_reverse_lookup_start.sh) to trigger the DNS Observer jobs.; Tip: Alternatively, you can set the appropriate environment variables. If an environment variable is set, it takes precedence over the configuration file settings.

You define and start the following jobs. You must edit the parameters in the configuration file before running these jobs.

Forward lookup job: A transient (one-off) job that loads all requested DNS forward lookup topology data.; This job is started by the dns_observer_forward_lookup_start.sh script.
Reverse lookup job: A transient (one-off) job that loads all requested DNS reverse lookup topology data.; This job is started by the dns_observer_reverse_lookup_start.sh script.

Procedure

Open the dns_observer_common.sh configuration file and edit the required parameters.

type

Values can be either forward for name-to-IP address lookups, or reverse for IP address-to-name lookups.

address_type

IPV4 or IPV6

server

The DNS server IP address

port

The DNS server port number

recurse

Values can be false to run the job without recursion, or true to initiate recursion, with the maximum number of calls set at 200.

domain_name

The domain name for the DNS forward lookup job

ip_address

The IP address for the DNS reverse lookup job

Run the jobs

To start the DNS forward lookup job, use the following command:
```
$ASM_HOME/bin/dns_observer_forward_lookup_start.sh
```
To start the DNS reverse lookup job, use the following command:
```
$ASM_HOME/bin/dns_observer_reverse_lookup_start.sh
```

Results

Data retrieved from the DNS query is displayed in the Agile Service Manager Topology Viewer.

Example

Example of a forward DNS Observer job with no recursive lookup:

{
  "unique_id": "my job",
  "type": "forward",
  "parameters": {
    "address_types": "IPV4",
    "server": "8.8.8.8",
    "port": 53,
    "recurse": false,
    "domain_name": "yourdomain.com"
  }
}

Example of a reverse DNS Observer job with recursive lookup:

{
  "unique_id": "my job",
  "type": "reverse",
  "parameters": {
    "address_types": "IPV4",
    "server": "8.8.8.8",
    "port": 53,
    "recurse": true,
    "ip_address": "8.8.8.8"
  }
}

What to do next

You can also use the following scripts:

dns_observer_lookup_stop.sh: Stops the DNS observer lookup job
dns_observer_job_list.sh: Lists the status of current jobs
dns_observer_log_level.sh: Sets the log level

Remember: In addition to being configurable from the Observer Configuration UI, all on-prem observer jobs also have scripts to start and stop all available jobs, to list the status of a current job, and to set its logging levels. Scripts can be run with -h or --help to display help information, and with -v or --verbose to print out the details of the actions performed by the script, including the full cURL command. For the on-prem version of Agile Service Manager, observer scripts are configured for specific jobs by editing the script configuration files.