Skip to main content

Pact server

The pact server is a stand-alone interactions recorder and verifier, aimed at clients that are non-JVM or non-Ruby based.

The pact client for that platform will need to be implemented, but it only be responsible for generating the JSON interactions, running the tests and communicating with the server.

The server implements a JSON REST Admin API with the following endpoints.

/         -> For diagnostics, currently returns a list of ports of the running mock servers.
/create -> For initialising a test server and submitting the JSON interactions. It returns a port
/complete -> For finalising and verifying the interactions with the server. It writes the `JSON` pact file to disk.
/publish -> For publishing contracts. It takes a contract from disk and publishes it to the configured broker

Running the server

Pact server takes the following parameters:

Usage: pact-jvm-server [options] [port]

port to run on (defaults to 29999)
prints this usage text
-h <value> | --host <value>
host to bind to (defaults to localhost)
-l <value> | --mock-port-lower <value>
lower bound to allocate mock ports (defaults to 20000)
-u <value> | --mock-port-upper <value>
upper bound to allocate mock ports (defaults to 40000)
-d | --daemon
run as a daemon process
-v <value> | --pact-version <value>
pact version to generate for (2 or 3)
-k <value> | --keystore-path <value>
Path to keystore
-p <value> | --keystore-password <value>
Keystore password
-s <value> | --ssl-port <value>
Ssl port the mock server should run on. lower and upper bounds are ignored
-b <value> | --broker <value>
The baseUrl of the broker to publish contracts to (for example
-t <value | --token <value>
API token for authentication to the pact broker
run with debug logging

Using trust store

Trust store can be used. However, it is limited to a single port for the time being.

Using a distribution archive

You can download a distribution from maven central. There is both a ZIP and TAR archive. Unpack it to a directory of choice and then run the script in the bin directory.

Building a distribution bundle

You can build an application bundle with gradle by running:

$ ./gradlew :pact-jvm-server:installdist

This will create an app bundle in build/install/pact-jvm-server. You can then execute it with:

$ java -jar pact-jvm-server/build/install/pact-jvm-server/lib/pact-jvm-server-4.0.1.jar

or with the generated bundle script file:

$ pact-jvm-server/build/install/pact-jvm-server/bin/pact-jvm-server

By default will run on port 29999 but a port number can be optionally supplied.

Running it with docker

You can use a docker image to execute the mock server as a docker container.

$ docker run -d -p 8080:8080 -p 20000-20010:20000-20010 uglyog/pact-jvm-server

This will run the main server on port 8080, and each created mock server on ports 20000-20010. You can map the ports to any you require.

Life cycle

The following actions are expected to occur

  • The client calls /create to initialise a server with the expected JSON interactions and state
  • The admin server will start a mock server on a random port and return the port number in the response
  • The client will execute its interaction tests against the mock server with the supplied port
  • Once finished, the client will call `/complete' on the Admin API, posting the port number
  • The pact server will verify the interactions and write the JSON pact file to disk under /target
  • The mock server running on the supplied port will be shutdown.
  • The client will call /publish to publish the created contract to the configured pact broker



The client will need POST to /create the generated JSON interactions, also providing a state as a query parameter and a path.

For example:

POST http://localhost:29999/create?state=NoUsers&path=/sub/ref/path '{ "provider": { "name": "Animal_Service"}, ... }'

This will create a new running mock service provider on a randomly generated port. The port will be returned in the 201 response:

{ "port" : 34423 }

But you can also reference the path from /sub/ref/path using the server port. The service will not strip the prefix path, but instead will use it as a differentiator. If your services do not have differences in the prefix of their path, then you will have to use the port method.


Once the client has finished running its tests against the mock server on the supplied port (in this example port 34423) the client will need to POST to /complete the port number of the mock server that was used.

For example:

POST http://localhost:29999/complete '{ "port" : 34423 }'

This will cause the Pact server to verify the interactions, shutdown the mock server running on that port and writing the pact JSON file to disk under the target directory.


Once all interactions have been tested the /publish endpoint can be called to publish the created pact to the pact broker For this it is required to run the pact-jvm-server with the -b parameter to configure the pact broker to publish the pacts to. Optionaly an authentication token can be used for authentication against the broker.

For example:

POST http://localhost:29999/publish '{ "consumer": "Zoo", "consumerVersion": "0.0.1", "provider": "Animal_Service" }'

This will cause the Pact server to check for the pact Zoo-Animal_Service.json on disk under target and publish it to the configured pact broker. After a successful publish the pact will be removed from disk.


The / endpoint is for diagnostics and to check that the pact server is running. It will return all the currently running mock servers port numbers.

For example:

GET http://localhost:29999/

'{ "ports": [23443,43232] }'