Dropwizard-Nagios

Extends Dropwizard's Task component to return Nagios-formatted healthchecks.

So, why not just repurpose Dropwizard's HealthCheck?

The Dropwizard (Yammer/Codahale) HealthCheck facility does not provide the granularity we desire. We really like (nay prefer) the Nagios reporting standard which not only includes four valid service states (OK, WARN, CRITICAL, UNKNOWN), but also allows the output of Perf Data (performance data), which are arbitrary metrics specific to a health check. While we get some of the same capabilities in different ways with Dropwizard's Metrics, we really want the ability to have this all integrated into one solution.

Release Notes

1.1.0 Refactored the Nagios check script to be more idiomatic. Fixed a couple of warts in the model that was representative of the old JSendNSCA project.

1.0.1 Fixed a dependency issue that was causing the build to fail.

Installation

Access via Maven:

<repositories>
  <repository>
    <id>nexus.bericotechnologies.com</id>
    <name>Berico Technologies Nexus</name>
    <url>http://nexus.bericotechnologies.com/content/groups/public</url>
    <releases><enabled>true</enabled></releases>
  </repository>
</repositories>

<dependencies>
  <dependency>
    <groupId>com.bericotech</groupId>
    <artifactId>dropwizard-nagios</artifactId>
    <version>1.1.0</version>
  </dependency>
</dependencies>

Installing the Nagios Check Plugin:

1. Install the Python dependencies: pynag and requests:

sudo pip install requests
sudo pip install pynag

Usage

Writing a Nagios HealthCheck in Java

To write a Nagios HealthCheck in Java, simply extend the com.bericotech.dropwizard.nagios.NagiosCheckTask class:

public class ExampleNagiosCheckTask extends NagiosCheckTask {

    public DemoCheckTask() {

        super("demo-check");
    }

    @Override
    public MessagePayload performCheck(ImmutableMultimap<String, String> requestParameters) throws Throwable {

        return MessagePayload
                .builder()
                .withLevel(Level.OK)
                .withMessage("Everything is OK!")
                .withPerfData(
                    PerfDatum.builder("sproketCount", 42).build()
                )
                .build();
    }
}

There is a more detailed example here: src/test/java/com/bericotech/dropwizard/nagios/ExampleNagiosCheckTask.java.

Adding Nagios HealthChecks to Dropwizard.

NagiosCheckTasks are Dropwizard Tasks. Therefore, they are added the same way. Simply all environment.addTask(nagiosCheckTask); to add it to the Dropwizard runtime.

For example, if we created a custom bundle:

public class ExampleNagiosBundle implements Bundle {

    @Override
    public void initialize(Bootstrap<?> bootstrap) {}

    @Override
    public void run(Environment environment) {

        environment.addTask(new ExampleNagiosCheckTask());
    }
}

This example can be found here: src/test/java/com/bericotech/dropwizard/nagios/ExampleNagiosBundle.java.

Creating the Check Task in Nagios.

Add the check_url.py to the Nagios/Icinga plugin directory.

To get all of the options to check_url.py, execute: python check_url.py --help.

A simple example is found in the integration tests: PassingTask:

python check_url.py -u admin -p admin -H localhost -P 11112 -U tasks/passing-task?param1=value

Which returns:

OK - success

Parameters should be added to the relative path parameter -U. These parameters will be made available to the task in as entries in the ImmutableMultimap<String, String> passed to all NagiosCheckTask instances.

For example, in the integration tests, there is a task called ParameterizedTask. This can be executed against a locally launched Dropwizard instance like so:

python check_url.py -u admin -p admin -H localhost -P 11112 -U 'tasks/parameterized-task?p1=value1&p2=value2'

Which returns:

OK - success w/ p1=value1 and p2=value2

Please take note of the use of quotes for the parameters. If you do not, the text after the ampersand (&) will be interpreted by BASH as a separate command.

Contributions and Legal Information

Credits

Some of the code is borrowed from the JSENDNSCA project written by Raj.Patel (https://code.google.com/p/jsendnsca/).

License

This project is licensed under the Apache Software Foundation's License 2.0.

The MessagePayload, MessagePayloadBuilder, Level have been partially rewritten from the JSendNSCA library, which is also licensed Apache 2.0.