Consul Querying Nodes - Consul

What is Consul Querying Nodes?

In this section, we will study how to query nodes with the resulting functions −

  • Using dig
  • Using the Monitor command
  • Using the Watch command
  • By Registering External Services

Let us appreciate each of these functions in detail.

Using Dig

Consul takes note on 127.0.0.1:8600 for DNS queries in the consul. The way it controls which nodes are obtainable to deliver a service is using checks that can be either −

  • A Script that is executed and it returns a nagios compliant code.
  • An HTTP check that returns an HTTP response code.
  • A TCP check that is checking if a port is open.

The overall command for trying out dig is −

Currently, let us try out a example dig command –

The output would be as shown in the resulting screenshot.

dig

Using the Monitor Command

It is used to link and show the logs of a running Consul agent. This command will display the recent logs. It also lets you to log the agent at a comparatively high log level. It contains of many log levels, which you can track, such as – Trace, Debug, Info, Warn and Err.
Let us try out the resulting command −

The output would be as shown in the resulting screenshot.

monitor_command

You can also set the monitor command by means of the sub-commands such as -log-level and -rpc-address. By default, the address of the RPC is 127.0.0.1:8400. For more info, click here.

Using the Watch Command

This command offers us with a mechanism to watch for deviations in the list of nodes, service members, key value, etc. It also appeals a procedure with the newest values of the view. If no procedure is specified, the current values are treated to STDOUT, which can be a beneficial way to inspect data in Consul. The Consul Watch Command help has a selection of different choices as shown in the resulting screenshot –

watch_command

Let us try out a demo with -type = service as shown in the following command.

watch_type

For more data on this topic, you can click here.

By Registering External Services

Once recorded, the DNS interface will be able to return the suitable ‘A Records’ or CNAME Records for the service. Let us register an exterior service, such as Amazon as shown in the resulting code block and the screenshot as well.

registering_external_services

The above command states a service named as shop. This Node is called as amazon with its URL obtainable at www.amazon.com on Port 80. Let us check the output on consul to make sure we have properly installed this service. For this, please open the browser window at localhost:8500.

registering_external_services1

To remove the service, we can simply use the following command.

remove_service

Let us check the UI for it as shown in the resulting screenshot.

remove_service1

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