---
layout: post
title:  "Optimizer Plan Visualization Tool"
date:   2014-01-26 9:00:00
categories: news
---

Stratosphere's hybrid approach combines **MapReduce** and **MPP database** techniques. One central part of this approach is to have a **separation between the programming (API) and the way programs are executed** *(execution plans)*. The **compiler/optimizer** decides the details concerning caching or when to partition/broadcast with a holistic view of the program. The same program may actually be executed differently in different scenarios (input data of different sizes, different number of machines).

**If you want to know how exactly the system executes your program, you can find it out in two ways**:

  1. The **browser-based webclient UI**, which takes programs packaged into JARs and draws the execution plan as a visual data flow (check out the [documentation](http://stratosphere.eu/docs/0.4/program_execution/web_interface.html) for details).
 
  2. For **programs using the [Local- ](http://stratosphere.eu/docs/0.4/program_execution/local_executor.html) or [Remote Executor] (http://stratosphere.eu/docs/0.4/program_execution/remote_executor.html)**, you can get the optimizer plan using the method `LocalExecutor.optimizerPlanAsJSON(plan)`. The **resulting JSON** string describes the execution strategies chosen by the optimizer. Naturally, you do not want to parse that yourself, especially for longer programs.

  The builds *0.5-SNAPSHOT* and later come with a **tool that visualizes the JSON** string. It is a standalone version of the webclient's visualization, packed as an html document `tools/planVisualizer.html`.

  If you open it in a browser (for example `chromium-browser tools/planVisualizer.html`) it shows a text area where you can paste the JSON string and it renders that string as a dataflow plan (assuming it was a valid JSON string and plan). The pictures below show how that looks for the [included sample program](https://github.com/stratosphere/stratosphere/blob/release-0.4/stratosphere-examples/stratosphere-java-examples/src/main/java/eu/stratosphere/example/java/record/connectedcomponents/WorksetConnectedComponents.java?source=cc) that uses delta iterations to compute the connected components of a graph.

<img src="{{ site.baseurl }}/img/blog/plan_visualizer1.png" style="width:100%;">

<img src="{{ site.baseurl }}/img/blog/plan_visualizer2.png" style="width:100%;">