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A HTTP debugging proxy that helps you with your continuous deployments
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Latest commit 018e7b2 Jun 16, 2013 @kelvl kelvl Fixing merge issue on README

Shadow Proxy


Shadow is a HTTP debugging proxy that sits in front of an existing service and a service with new code changes. It copies and directs incoming requests to both downstream services and compares the responses from those services.

Shadowing deployments allows users to assert expected behaviors on the new codebase and detect unexpected behavioral changes before pushing new code into production.

Shadow comes with a UI that allows users to monitor the stream of requests live.


  1. Java 1.6+
  2. SBT 0.12.1+


  1. Clone the repository: git clone
  2. Build the JAR: sbt assembly

This generates an assembled Jar with all dependencies in /target/shadow-assembly-<VERSION>.jar


No escalated privledges needed unless you are using privileged ports. Just copy the Jar built in the previous step on to your existing server.


Make a copy of the example configuration application.conf.example and change the settings to fit your environment.

Shadow specific configuration

akka {
  loglevel = INFO

shadow {
    version = "0.1-SNAPSHOT"

    proxy-host = localhost
    proxy-port = 8000

    ui-host = localhost
    ui-port = 8081

    results-log = "logs/results.log"

    trueServer {

        host = ""
        port = 80

        query-param-overrides {

        form-param-overrides {


    shadowServer {

        host = ""
        port = 80

        query-param-overrides {
            test = ["hello"]

        form-param-overrides {
            test2 = ["world"]


spray.can.server {
  server-header = shadow-server/${shadow.version}
  request-timeout = 15s
  stats-support = true

spray.can.client {
    user-agent-header = shadow/${shadow.version}


Running java -jar -Dconfig.file=application.conf shadow-assembly-<VERSION>.jar will start the server in the foreground.

We recommend using a supervisor such as jsvc or runit to manage running shadow

Be default, the UI can be accessed at http://localhost:8081


Tests are found under src/main/test/scala/

To run them, use: sbt test

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