Fast Parallel Async HTTP client as a Service to monitor and manage 10,000 web servers. (Java+Akka)
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Yuanteng (Jeff) Pei
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REST Commander: Parallel Async HTTP Client as a Service Travis status

Formerly known as REST Superman. Fire thousands of HTTP requests and aggregate responses in a couple of clicks in seconds. Please check detail instructions, screenshots, documentations, sample code, REST APIs, and demos at and its demo video. What's new? Check related work review on efficient HTTP clients and concurrency and throttling model in Akka at eBay tech blog.

REST Commander is a fast parallel async HTTP/REST/SOAP client as a service to monitor and manage 10,000s of web servers. Sends requests to 1000 servers with response aggregation in 10 seconds. or 10,000 servers in 50 seconds.

Need standalone library alternative? Try (released 2015.11). With the feedbacks, lessons, and improvements from the past year of internal usage and open source of REST Commander, we now made its core as an easy to use standalone library. We added 15+ new features, rewritten 70%+ of the code, with 90%+ test coverage for confident usage and contribution. The key benefits of Parallec are flexible response aggregation and ease to send the results anywhere.

REST Commander serves as the agent master of cronus-agent (open sourced) for scalable software deployment, script execution, config push, and monitoring.

Version 2.0.0 : faster than faster, by restructuring via AKKA remoting and clustering, we are able to make REST Commander distributed and horizontally scalable. Distributed REST Commander can send request to 100K+ machines in eBay's cloud and gather result back in just 100s using 5 VM.

Version 2.0.0 | What and Why | Highlights | Performance | Run Instructions

REST Commander has been in top 10 trending out of 10 millions+ projects in Github in all languages on 01/21/2014 and 01/22/2014. It has been recommended and listed in top 20 trending out of 28K+ software in oschina, the largest open source community in China. It has also been featured and front-paged at InfoQ.

Structure Overview

Version 2.0.0 : distributed REST Commander

We restructure REST Commander via AKKA remoting and clustering. Detailed information and API document at here. Workflow and architecture design details at here. See git branch distributed_commander.

New Features

  • Speed : By restructuring REST Commander to make it distributed and horizontally scalable, it can send request to 100K+ machines in eBay's cloud and gather result back in just 100s using 5 VM.
  • Reliability : Automatically failover in case of failure on slave node, and adjust sending speed to avoid network congestion.
  • Scheduling : Provide task scheduling to handle multitasks.
  • Visibility : Show workload and available capacity of each slave node, track task progress.

Workflow & Architecture

The main workflow of distributed REST Commander is shown as below.

Work Flow

Distributed REST Commander is based on AKKA. Each functionality component in the pictrue above is implemented as an AKKA actor (except Job Manager). The whole system is based on message passing model.

What is REST Commander and Why I need it?

Commander is Postman at scale: a fast parallel async http client as a service with aggregated response and regular expression based string extraction. It is in Java (with Akka and Play Framework).

So what can Commander do? It speaks HTTP at scale, thus is powerful with many use cases. Here are some basic ones for automation on managing and monitoring tens of thousands web servers (See Sample Code). Commander itself is also "as a service": with its powerful REST API, you can define ad-hoc target servers, an HTTP request template, variable replacement, and a regular expression all in a single call.

Whenever comes to sending multiple HTTP requests in parallel, federated data aggregation or scalable task executions on HTTP, Think Commander First.

  • Monitor HTTP web servers: are you a company who have 50-5,000 web servers (e.g. tomcat, nginx, etc... ) running; and want to check every minute which servers are slow or misconfigured? Commander can get this done for you in an hour.
  • Config push to HTTP web servers: If your servers use REST/SOAP APIs to update its config and you want to enforce server-specific or uniform config on demand or with auto-remediation. Commander is your perfect choice.
  • HTTP web server management work flows combining the above 2: e.g., discover unhealthy webservers and then conduct operations (restart, config push) to them.


  • Scalable and Fast: Utilizes Akka and Async HTTP Client to maximize concurrency; Sends and aggregates responses from 10,000+ Servers within 1 minute.
  • Powerful: Sends uniform or node-specific requests with near real-time response analysis or config pushes. Request level concurrency control.
  • Generic: Generic HTTP request. Generic response aggregation with user-defined regular expression matching. Generic variable replacement in request templates for node specific requests.
  • Ready to Use: Agility. Zero installation required. Changing requests and target servers with breeze. No database setup. Run locally in a single click.
  • User Friendly: Build in Java with Play Framework, Bootstrap and its Application Wizard, Commander enables sending requests in both easy-to-use web UI wizards and powerful REST APIs. Define ad hoc requests, target servers and the regex aggregation rule in a single REST call.
  • Agent-less Monitoring: Quickly check any HTTP results from an ad hoc list of servers with generic response aggregation by regular expression matching. FAST: No dependency or setup required.
  • Config Pushes: Push uniform config or node-specific configs to HTTP end points, as long as there are HTTP (REST/SOAP) APIs to perform.
  • N Requests to 1 Target: Concurrently fire a large number of different requests to a single target server. E.g. look up thousands of jobs status in a server. Concurrency control to accommodate server capacity.
  • IT Orchestration: Scalable multi-step HTTP work flows to thousands of HTTP endpoints.
  • Discover Outliers: Discover misconfigured servers from thousands of servers with http APIs in no time.
  • Remediation Automation: If your config change requests are idempotent, Commander can easily ensure correct config by scheduled config pushes.

Commander is powerful to send (1) the same request to different servers; (2) different requests to different servers; (3) different requests to the same server. Why we need them? Check out these live examples on (1) monitor websites; (2) poll job status (3) call the same weather WSDL web service with different zip codes.

Performance (SLA)

  • Measured from Commander running on a single off-the-shelf server.
  • 1000 servers requests and all responses aggregated in 7 seconds
  • 10,000 servers requests and all responses aggregated in 48 seconds
  • 20,000 servers requests and all responses aggregated in 70 seconds
  • 20,000 is far less than the maximum scale we tested and it is stable for months. We have not been able to find the scalability limit. :-)

Run Instructions

Directly Under Windows/Linux With Zero Installation:

  • Assuming have Java (JDK or most time just JRE) pre-installed.
  • double click: start_application_win.bat . Just close the window to shutdown the server.
  • Then open browser: localhost:9000
  • After shutdown the application: double click: clean_application_pid_after_run_win.bat
  • Note that for Linux/Mac user: need to chmod +x for play-1.2.4/play
  • sh /home/user/RestCommander/ start

Run/Debug With Eclipse:

  • Clone project in Git from:
  • Extract to a folder, e.g., S:\GitSources\AgentMaster\AgentMaster. In command line run: S:\GitSources\AgentMaster\AgentMaster>play-1.2.4\play eclipsify AgentMaster
    • Note that for Linux/Mac user: need to chmod +x for play-1.2.4/play
  • Import existing project in Eclipse: import the AgentMaster folder.
  • Compile errors? Try rebuild and clean: (menu: Project->Clean->Clean all projects
  • Run application: under "eclipse" folder: AgentMaster.launch : run as AgentMaster
  • Then open browser: localhost:9000


Key files are under conf folder

  • agentcommand.conf : defines commands
  • nodegroup.conf : defines the node list: ad hoc; from ODB; from Statehub.
  • aggregation.conf : defines aggregation: using the default one to parse number out.
  • application.conf : play settings
  • actorconfig.conf : Akka settings
  • routes : MVC settings as dispatcher


  • Under windows: shutdown in the middle of sending requests or many requests: No buffer space available (maximum connections reached ?)

About REST Commander


REST and SOAP API (HTTP GET/POST/PUT/DELETE) has become the dominant approach in current platform and services. However, efficient REST / SOAP calls to multiple servers in parallel with server-specific requests and aggregated response analysis are still challenging.

Problem Statement:

Design and implement a user friendly and generic HTTP client able to conduct efficient HTTP calls to a large amount of servers in parallel with uniform or server-specific requests and aggregated response analysis.


  • Improve HTTP/SOAP/REST call efficiency by 100%-5000% with 3-15000 target nodes in parallel, compared to single server POSTMAN or sequential executed none-generic shell scripts.
  • Enable any uniform or server-specific REST (GET/POST/PUT/DELETE) calls to servers for periodical monitoring and configuration pushes in a simple UI with fast and reliable with responses aggregation. Automate tens of thousands of server's management and software pool management.
  • Innovation: After thoroughly reviewing related work of Postman, JMeter, Gatling, Apache Bench, Typhoeus and many other publication or tools, we are not aware of any existing ones are able to achieve the same speed, scale and functionality of generic response aggregation.

REST API Example

REST Commander supports both intuitive step-by-step wizards and REST APIs. Here is an simple example of uniform request to 3 target servers. In this example, the command and aggregation rule have been pre-defined. More complex API examples using none pre-defined command or aggregation rules can be found here.

Request: (assuming Commander runs on localhost:9000)

HTTP POST to: http://localhost:9000/commands/genUpdateSendCommandWithReplaceVarMapAdhocJson POST Body:



	"aggregationMap": {
		"23.54": "1",
		"27.08": "1",
		"7.08": "1"
	"aggregationValueToNodesList": [
			"value": "23.54",
			"nodeList": [
			"isError": false
			"value": "27.08",
			"nodeList": [
			"isError": false
			"value": "7.08",
			"nodeList": [
			"isError": false