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https://github.com/expediadotcom/haystack-dropwizard


https://github.com/expediadotcom/haystack-dropwizard

distributed-tracing dropwizard java opentracing

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README 

        
[![Build Status](https://travis-ci.org/ExpediaDotCom/haystack-dropwizard.svg?branch=master)](https://travis-ci.org/ExpediaDotCom/haystack-dropwizard)

[![License](https://img.shields.io/badge/license-Apache%20License%202.0-blue.svg)](https://github.com/ExpediaDotCom/haystack/blob/master/LICENSE)



## Table of Contents



- [Instrumenting dropwizard applications](#Instrumenting-dropwizard-applications)

- [Quick start](#quick-start)

  * [Haystack dropwizard dependency](#haystack-dropwizard-dependency)

  * [Usage](#Usage)

- [See Also](#See-also)



## Instrumenting dropwizard applications

One can use haystack-dropwizard to instrument dropwizard applications and send tracing information to open tracing compliant [Haystack](https://expediadotcom.github.io/haystack) server distributed tracing platform.



This library in turn use [haystack-client-java](https://github.com/ExpediaDotCom/haystack-client-java) which provides an implementation of `io.opentracing.Tracer` and helps create an instance of it.



## Quick Start

This section provides steps required to quickly configure your dropwizard application, to be wired using [OpenTracing JAX-RS Instumentation](https://github.com/opentracing-contrib/java-jaxrs)'s dropwizard integration to haystack.

If you need additional information, please read the subsequent sections in this document.



# Haystack dropwizard dependency

Add the following dependency to your application.



```

   

        com.expedia.www

        haystack-dropwizard

        ${haystack-dropwizard.version}

   

```



# Usage

To make use of the depency to create and manage traces one needs to do the following.



Instantiate a `HaystackTracerBundle` to be passed to your dropwizard application while bootstrapping. 

Also in case we need to trace the client requests emanating from this app we need to register the clienttracing feature with the client to be used. 

Here is a short example:



```

public class FrontendApplication extends Application {

    

    // This bundle needs to be always initialised and passed to the app while bootstrapping.

    // bundle that initializes an instance of io.opentracing.Tracer

    private final HaystackTracerBundle haystackTracerBundle = new HaystackTracerBundle<>();



    // Here we are adding the bundle

    @Override

    public void initialize(Bootstrap bootstrap) {

        // the following line initializes server tracing and entertains @Traced

        // annotations on Resource methods

        bootstrap.addBundle(this.haystackTracerBundle);

    }



    // If we need to trace client requests emanating from the app,

    // We need to register the clienttracingfeature with the client and then use this client to make the requests.

    @Override

    public void run(HelloWorldConfiguration helloWorldConfiguration,

                    Environment environment) {

        // the following line registers ClientTracingFeature to trace all

        // outbound service calls

        final Client client = ClientBuilder.newBuilder()

                .register(this.haystackTracerBundle.clientTracingFeature(environment))

                .build();



        environment.jersey().register(new Frontend(client));

    }

}

```



Also in the configuration yaml file for the application usually named config.yml, one needs to add the following snippet

with appropriate configs:



For local dispatch, means the traces will not be sent to the haystack server instead they will only be written to local file

```

tracer:

  serviceName: Backend

  enabled: true

  dispatchers:

    - type: logger

      loggerName: dispatcher

```



For remote dispatch, means the traces will be sent to the haystack server using the haystack client

```

tracer:

  serviceName: Backend

  enabled: true

  dispatchers:

    - type: remote

      client:

        type: agent

        host: localhost

        format:

          type: protobuf

```



To find the full example check this example of a simple application with client and server side tracing enabled,

[Haystack Dropwizard Example](https://github.com/ExpediaDotCom/haystack-dropwizard-example).



To check how blobs feature work with tracing, check this example of a simple application with client and server side

[Haystack Blob Example](https://github.com/ExpediaDotCom/haystack-blob-example).



## See Also 

This library is built on top of [Haystack client java](https://github.com/ExpediaDotCom/haystack-client-java).



Further resources:  

[JAX-RS2]: https://jax-rs.github.io/apidocs/2.1/  

[Jersey]: https://jersey.java.net  

[Dropwizard]: http://www.dropwizard.io  

[Opentracing JAX-RS instrumentation]: https://github.com/opentracing-contrib/java-jaxrs