The Develocity Test Distribution agent executes tests triggered from Gradle or Maven builds on remote machines. Please consult the Develocity Test Distribution User Manual for information on build configuration.

Use of the Develocity Test Distribution agent software is subject to the Develocity Software Agreement.

Agents need to be connected to a Develocity server.

The Develocity Test Distribution agent is distributed as a Docker image via Docker Hub, and as an executable JAR. Both distributions offer the same functionality.


CPU & memory

The agent itself needs about 128 MiB of memory and does not require significant CPU resources. However, you need to determine the total memory and CPU resources depending on the types of tests you intend to run on the agent. Two CPU cores and 2 GiB of memory are a good starting point for tests that are not particularly resource-intensive. If your tests start additional external processes, you’ll likely need more. Thus, you should monitor CPU and memory consumption of an agent while it’s executing a typical test workload.

Maximum heap size

The maximum heap size (and other memory options) of the forked Java VM that executes the tests can be configured by developers.

For Gradle builds, the maximum heap size can be configured via the maxHeapSize property and is limited to 512 MiB by default.

For Maven builds, Surefire/Failsafe lets the forked JVM determine the maximum heap size based on the machine’s physical memory by default. The outcome depends on the used JVM version and implementation and may not take into account memory restrictions when the agent runs in a Docker container on older versions of Java (see JDK-8146115). Therefore, it’s usually a good idea to configure -Xmx explicitly via the argLine configuration parameter.

Disk usage

The agent uses a local file cache to store JAR files and other artifacts that are required to execute tests. The cache directory is cleaned up periodically, so it does not grow indefinitely. How much space you’ll need depends on your tests and how often you’ve configured the cache directory to be cleaned up. Usually, a few hundred MiB should be sufficient. We recommend monitoring the directory size over the course of the cache’s retention period.


The agent requires a reasonably fast and stable connection to the Develocity server in order to operate efficiently. While running, the agent maintains a persistent WebSocket connection over default HTTP/HTTPS ports to the Develocity server.

In case your agents cannot connect to the Develocity server, please ensure all load balancers and proxies that are used between both ends support WebSocket connections.

If the connection is lost, e.g. when the server is restarted, the agent will periodically attempt to reconnect. Since all communication goes through the Develocity server, the agent does not need a direct connection to the machine that initiated test execution, e.g. the developer workstation or build server running the Gradle build, or vice versa. Moreover, since the connection to the Develocity server is initiated by the agent, it can be deployed to an internal network and does not need to be addressable from machines running builds.


Test Distribution allows remote code execution inside your infrastructure for authorized Develocity users. This is comparable to CI jobs which also execute tests that could theoretically run any command on the remote host. In addition, test code will be able to access the local file system including the local file cache which might include artifacts of other projects that have previously had their tests executed on the same agent. Thus, you should treat the infrastructure you run Test Distribution agents on similarly to those of regular CI agents.



You can download version 3.0.1 of the JAR here. Older versions of the JAR can be found in the appendix below.

The agent requires at least Java 21 to run and supports Linux, macOS, and Windows. Moreover, you need to specify the server, registration key, and pool parameters that are required to connect and register with the Develocity server.

java -Xms64m -Xmx64m -XX:MaxMetaspaceSize=64m \
    -jar develocity-test-distribution-agent-3.0.1.jar \
    --server https://«develocity-hostname» \
    --registration-key «registration-key» (1)
    --pool «pool-id» (2)
1 Registration key generated via Develocity administration
2 Agent pool configured via Develocity administration

You will see output similar to the following:

[…] Skipping cleanup of local file cache (next due on […])
[…] Successfully registered with https://«develocity-hostname» (will be refreshed in 1h)
[…] Agent (v3.0.1) started and connected to https://«develocity-hostname»


With Docker installed, you can start an agent using the following command:

docker run --detach \
    gradle/develocity-test-distribution-agent:3.0.1 \
    --server https://«develocity-hostname» \
    --registration-key «registration-key» (1)
    --pool «pool-id» (2)
1 Registration key generated via Develocity administration
2 Agent pool configured via Develocity administration

Alternatively, you can use environment variables to configure the agent:

docker run --detach \
    --env TEST_DISTRIBUTION_AGENT_SERVER=https://«develocity-hostname» \

The default Docker image has JDK 21 installed. You can extend the image should you wish to install additional JDKs or other software.

By default, the Docker image’s entrypoint passes -Xms64m -Xmx64m -XX:MaxMetaspaceSize=64m as JVM arguments to the agent JVM. You can override these JVM arguments by passing the TEST_DISTRIBUTION_AGENT_OPTS environment variable to the Docker container.

Airgapped hosts

In order to install the agent Docker image on a host that is not connected to the Internet (i.e. airgapped), you will need to first obtain the image on an Internet connected host, then transfer it to the airgapped destination.

  1. On the non-airgapped system, pull down the latest docker image for the node and export it to a file

    docker pull gradle/develocity-test-distribution-agent:3.0.1
    docker save gradle/develocity-test-distribution-agent:3.0.1 \
        --output develocity-test-distribution-agent.tar
  2. Copy this file across to the airgapped host, and then import the image into docker

    docker load --input develocity-test-distribution-agent.tar

The agent can then be started and configured on the airgapped host in the same manner as a non-airgapped install.


Below is a sample manifest for deploying agents to a Kubernetes cluster using the official agent Docker image. You may need to adjust its configuration, e.g. the configured CPU and memory requirements, based on the needs of your tests.

apiVersion: v1
kind: Secret
  name: develocity-test-distribution-api-key-secret
  namespace: default
  apiKey: «api-key» (1)
apiVersion: apps/v1
kind: Deployment
  name: develocity-test-distribution-agent
  labels: test-distribution-agent-«pool-id» (2) gradle-enterprise test-distribution-agent
    matchLabels: test-distribution-agent-«pool-id» (2) gradle-enterprise test-distribution-agent
      labels: test-distribution-agent-«pool-id» (2) gradle-enterprise test-distribution-agent
        runAsUser: 999
        runAsGroup: 0
        fsGroup: 0
      terminationGracePeriodSeconds: 600 (3)
      - name: develocity-test-distribution-agent
        image: gradle/develocity-test-distribution-agent:3.0.1 (4)
            memory: 1Gi
            cpu: 2
            memory: 4Gi
            cpu: 2
          value: https://«develocity-hostname»
              name: develocity-test-distribution-api-key-secret
              key: apiKey
          value: «pool-id» (2)
1 Registration key generated via Develocity administration
2 Agent pool configured via Develocity administration
3 The amount of time Kubernetes should wait for the agent to gracefully terminate.
4 The official or extended agent Docker image
Prior to Kubernetes v1.9, the deployment apiVersion: apps/v1 should be apiVersion: apps/v1beta1.


All configuration options can be specified via command-line arguments or environment variables whereby the former take precedence over the latter.


There are three mandatory parameters (environment variables) that are used to register with the Develocity server on startup:

-s/--server https://«develocity-hostname» (env: TEST_DISTRIBUTION_AGENT_SERVER)

The URL of the Develocity server the agent should connect to

-p/--pool «pool-id» (env: TEST_DISTRIBUTION_AGENT_POOL)

The identifier of a previously configured agent pool to which the agent should be assigned

-k/--registration-key «registration-key» (env: TEST_DISTRIBUTION_AGENT_REGISTRATION_KEY)

The pool-specific registration key to use for authenticating with the Develocity server

The agent sends the API key to the Develocity server when starting up and once every hour to renew its registration. If the API key is invalid or has been revoked by a Develocity administrator, the agent will print an error message and exit with a non-zero status code.

By default, the agent will not allow connections to Develocity if the server presents an untrusted certificate (e.g. self-signed). In order to allow such connections, you’ll have to use the following parameter (environment variable):

--allow-untrusted true/false (env: TEST_DISTRIBUTION_AGENT_ALLOW_UNTRUSTED)

Allow/forbid connecting to servers with untrusted (e.g. self-signed) SSL certificates (defaults to false)

Enabling this option is a security risk as it makes it easier for a third party to intercept communication between the agent and Develocity. It should only be used as a short term workaround until the server can be configured with a trusted certificate.

Finally, you may specify the agent name that will be shown on the Develocity Administration pages:

-n/--name «agent-name» (env: TEST_DISTRIBUTION_AGENT_NAME)

Descriptive agent name (defaults to hostname)


When registering with Develocity upon startup, the agents report a set of capabilities that will be matched against the requirements of test tasks. Please refer to the Test Distribution user manual for details on how to configure requirements for Gradle or Maven builds.

The agent auto-detects the operating system it is running on (currently supported are Linux, macOS, and Windows) and adds os=linux, os=macos, or os=windows to the set of capabilities.

Moreover, the agent infers installed JDKs from environment variables that match the JDK\d\d? regex and adds a capability for each of them. For example, if JDK8 and JDK11 are set to the paths of their corresponding Java home directories, the agent will automatically add jdk=8 and jdk=11 to the set of capabilities.

If you want to install additional software on a subset of your agents and use that as a criterion when selecting agents for test execution, you can use the following parameter (environment variable):

-c/--capabilities «capability»(,«capability»)* (env: TEST_DISTRIBUTION_AGENT_CAPABILITIES)

Comma-separated list of agent capabilities to match against build requirements

Capabilities may only contain alphanumeric characters, dashes, underscores, periods, and a single equals sign.

For example, the following invocation would make the agent register with the additional docker and postgres=12 capabilities:

java -jar develocity-test-distribution-agent-3.0.1.jar […] \
     --capabilities docker,postgres=12

While the exact semantics are up to you, this might indicate that the tests on that agent can use Docker and PostgreSQL in version 12.

Local file cache

The following parameters (environment variables) can be used to configure the local file cache:

--cache-dir «dir» (env: TEST_DISTRIBUTION_AGENT_CACHE_DIR)

Directory to use for the local file cache (defaults to «user-home»/.develocity-test-distribution-agent/file-cache)

--cache-cleanup true/false (env: TEST_DISTRIBUTION_AGENT_CACHE_CLEANUP)

Enable/disable cleanup of the local file cache (defaults to true)

--cache-cleanup-interval «duration» (env: TEST_DISTRIBUTION_AGENT_CACHE_CLEANUP_INTERVAL)

Interval in which the local file cache should be cleaned up (defaults to PT24H, i.e. 24 hours)

--cache-retention-period «duration» (env: TEST_DISTRIBUTION_AGENT_CACHE_RETENTION_PERIOD)

Period for which entries in the local file cache should be retained (defaults to PT168H, i.e. 7 days)

Sharing the local file cache among several agents running on the same host is currently not supported. If you are running more than one agent on the same host make sure to configure individual cache directories for each agent or use the Docker image.

Auto scaling

General setup

In order to scale the number of agents based on demand, i.e. how many tests need to be executed at any given moment, Develocity uses the concept of an agent pool. In general, the steps to set up an auto scaling pool of agents are as follows:

  1. Create and configure an agent pool on the administration pages of Develocity.

  2. Configure your agents to register with the ID of the pool via the --pool option.

  3. Configure your compute platform to query the pool’s status at regular intervals.

  4. Start/stop agents in accordance with the value of the desiredAgents property in the JSON response.

Stopping agents gracefully

When scaling down, compute platforms may stop an agent that is running tests. Care should be taken in how the agents are stopped to allow agents to finish any in-flight tests.

To do this, first send the TERM signal to an agent you wish to stop and wait for a certain grace period before sending it the KILL signal. When receiving a TERM signal, the agent notifies the build that it needs to stop and terminates gracefully after finishing the current set of tests. The duration of the grace period depends on the nature of your tests — it should allow your slowest test classes to finish.

The docker stop command provides a --time option with this behaviour. The TERM signal will be sent immediately, with a KILL signal being sent if the agent has not stopped within the given --time setting. Kubernetes provides a terminationGracePeriodSeconds parameter that provides the same behaviour.

If an agent is killed before it is allowed to stop gracefully, the set of tests that it was assigned will be rescheduled for execution by another agent. This may cause some tests that had already been executed by the stopped agent to be executed again.


In order to configure your agents to register with the ID of a previously configured agent pool, the simplest option is to pass the TEST_DISTRIBUTION_AGENT_POOL environment variable as demonstrated in the deployment manifest in the installation section.

For scaling the number of replicas in the deployment based on demand, using the lightweight and open source KEDA (minimum version 2.5) component is recommended.

First, deploy KEDA to your Kubernetes cluster (e.g. using the provided Helm chart). Then, create a KEDA ScaledObject in your cluster. Behind the scenes, KEDA sets up a standard Horizontal Pod Autoscaler (HPA), queries the pool’s status in Develocity according to the configured pollingInterval, and configures the HPA to scale according to the value of the desiredAgents property in the JSON response.

The following manifest is all you need to set up auto scaling of agents in an agent pool in your Kubernetes cluster:

apiVersion: v1
kind: Secret
  name: develocity-test-distribution-access-key-secret
  namespace: default
  accessKey: «access-key» (1)
kind: TriggerAuthentication
  name: develocity-test-distribution-agent-credentials
  - parameter: token
    name: develocity-test-distribution-access-key-secret
    key: accessKey
kind: ScaledObject
  name: develocity-test-distribution-agent-scaler
    name: develocity-test-distribution-agent
  minReplicaCount: 1 (2)
  maxReplicaCount: 100 (2)
  pollingInterval: 15 (3)
  - type: metrics-api
      url: https://«develocity-hostname»/api/test-distribution/agent-pools/«pool-id»/status (4)
      authMode: "bearer"
      valueLocation: desiredAgents
      targetValue: '1'
      name: develocity-test-distribution-agent-credentials
          stabilizationWindowSeconds: 60 (5)
1 Access key of a user with the “Test Distribution“ access control permission
2 The minimum/maximum number of replicas should match the configuration of the agent pool in Develocity
3 How frequently KEDA should query the agent pool’s status
4 The URL of the agent pool status endpoint in Develocity
5 How long agents should stay connected after a drop in demand before being stopped. You may want to customize this setting depending on how long it takes to spin up nodes in your cluster.


The “Usage” tab in Develocity visualizes the historical usage of agent pools, including the number of utilized (i.e. actually in use), connected (i.e. available to be utilized) and desired (i.e. that could be utilized if available) agents.

agent pool usage

Appendix A: Release history


14th May 2024
  • [NEW] Update JDK in Docker image to 21.0.3-10

  • [FIX] WebSocket exceptions are treated as non-recoverable errors and lead to build failures

Compatible with Develocity 2024.1 or later.


2nd April 2024
  • [NEW] Test Distribution Agent Image provides JDK 21

  • [NEW] Rename Test Distribution agent from Gradle Enterprise to Develocity

  • [NEW] Develocity Test Distribution agent requires a Java 21 runtime environment

  • [NEW] Update the base Docker image to ubuntu:jammy-20240125

Compatible with Develocity 2024.1 or later.


5th December 2023
  • [NEW] The official Docker image is now based on ubuntu:jammy to include the latest security updates

Compatible with Develocity 2023.4 or later.


14th September 2023
  • [FIX] Update to Java 17.0.8-7 for security updates and bug fixes

Compatible with Develocity 2023.1 or later.


22nd June 2023
  • [FIX] Upgrade libssl to address CVE-2023-2650

Compatible with Develocity 2023.1 or later.


3rd May 2023
  • [FIX] Update JDK in Docker image to 17.0.7

  • [FIX] Update Ubuntu packages in Docker image

Compatible with Develocity 2023.1 or later.


11th April 2023
  • [NEW] Test Distribution agent JAR is compiled for and requires Java 17

  • [NEW] Official Docker image includes JDK 17 instead of JDK 11

  • [NEW] Reconnect to Develocity on 404 responses after prior successful connection

Compatible with Develocity 2023.1 or later.


8th December 2022
  • [NEW] Improve error messages in case JDK auto-detection fails

  • [FIX] Update JDK Docker base image to JDK 11.0.17

Compatible with Develocity 2021.3 or later.


12th October 2022
  • [NEW] Use test-distribution-agent/<version> as User-Agent for HTTP requests

  • [FIX] Avoid writing to temporary workspaces after worker was asked to stop

  • [FIX] NullPointerExceptions on shutdown caused by prematurely stopped workers

Compatible with Develocity 2021.3 or later.


2nd September 2022
  • [NEW] Update JDK Docker base image to JDK

Compatible with Develocity 2021.3 or later.


10th August 2022
  • [NEW] Update JDK Docker base image to JDK 11.0.16

Compatible with Develocity 2021.3 or later.


11th July 2022
  • [FIX] Improve observability of sporadic file download failures

Compatible with Develocity 2021.3 or later.


2nd May 2022
  • [NEW] The official Docker image is now based on ubuntu:focal and bellsoft/liberica-openjdk-debian:11.0.15 to include the latest security updates

Compatible with Develocity 2021.3 or later.


19th April 2022
  • [NEW] Update JDK base images to 11.0.14 to apply latest security fixes

Compatible with Develocity 2021.3 or later.


31st March 2022
  • [NEW] Make WebSocket ping interval configurable via internal system property

Compatible with Develocity 2021.3 or later.


17th March 2022
  • [NEW] The official Docker image is now based on eclipse-temurin:11-focal instead of adoptopenjdk/openjdk11

Compatible with Develocity 2021.3 or later.


12th January 2022

Compatible with Develocity 2021.3 or later.


22nd December 2021

Compatible with Develocity 2021.3 or later.


15th December 2021

Compatible with Develocity 2021.3 or later.


13th December 2021

Compatible with Develocity 2021.3 or later.


29th September 2021
  • Fix race when agent is asked to stop working while starting to work is still in progress

Compatible with Develocity 2021.3 or later.


15th September 2021
  • Change communication protocol to avoid illegal reflective access

Compatible with Develocity 2021.3 or later.


1st June 2021
  • Update base Docker image to adoptopenjdk/openjdk11:jdk-11.0.10_9-ubuntu

  • Time out and retry when upgrading a connection to WebSockets hangs

  • Add --version option

  • Add --pool option

  • Perform version compatibility checks during registration with Develocity

  • Handle SIGTERM by signalling the current job and waiting for it to finish

Compatible with Develocity 2021.2 or later.


7th April 2021
  • Added basic self-healing functionality to local file cache by quarantining corrupt cache entries and re-downloading them when they are next requested

  • Fixed race between re-connection and registration to Develocity that could cause the agent to exit due to an authorization error

  • Reduced logging severity of connection errors

Compatible with Develocity 2021.1 or later.


15th March 2021
  • Fix race condition when agent is released shortly after being assigned

Compatible with Develocity 2021.1 or later.


3rd February 2021
  • Agent keeps reconnecting to Develocity for one hour in case the server url cannot be resolved

  • Input file archives are now sanity checked before unpacking to ensure only regular files and directories are created inside the target directory (CVE-2021-26719)

Compatible with Develocity 2020.5 or later.


17th December 2020
  • Deliberately cancelled downloads are no longer logged as errors

  • Illegal reflective access warnings no longer pollute the agent log

  • Memory options are applied by default when using the Docker image

  • Regression in local file cache cleanup is fixed

  • Agent keeps reconnecting to Develocity in case of a temporary DNS lookup failure

  • Fix sporadic ArithmeticException when reconnecting to the Develocity server

Compatible with Develocity 2020.5 or later.


8th December 2020
  • Retry file transfer on more intermittent failure types

Compatible with Develocity 2020.5 or later.


27th October 2020
  • Unresponsive network connections are now detected and closed proactively

Compatible with Develocity 2020.4 or later.


31st July 2020
  • Downloads that fail due to unexpectedly closed connections are now retried

  • Download failures are reported to the build in all cases

Compatible with Develocity 2020.3 or later.


29th July 2020
  • Downloaded files are now always closed before storing them in the local file cache

Compatible with Develocity 2020.3 or later.


27th July 2020
  • Input files are now downloaded in parallel from the file cache on the Develocity server instead of being requested from connected builds directly

  • Agent jar is published alongside its signature

  • Improved retry handling in case of connection errors

  • Docker image no longer uses the JAVA_OPTS environment variable to avoid inheriting it to test VMs and their child processes

Compatible with Develocity 2020.3 or later.


5th May 2020
  • Initial release

Compatible with Develocity 2020.2 or later.

Appendix B: Develocity Test Distribution Agent JAR downloads

Appendix C: (Legacy) Gradle Enterprise Test Distribution Agent JAR downloads

Appendix D: Compatibility with Develocity

Compatibility between versions of Develocity and the Develocity Test Distribution agent can be found here.

Appendix E: Extending the Docker image

The Docker image is based on the official Ubuntu Linux image (ubuntu:jammy) so installing additional dependencies is easy. It includes a BellSoft Liberica distribution of OpenJDK 21.

A common use case is to install additional JDKs or other software packages. In the example below, OpenJDK 11 is added using a multistage build along with the zip and unzip Ubuntu packages.

FROM --platform=linux/amd64 bellsoft/liberica-openjdk-debian:11 AS openjdk11

FROM gradle/develocity-test-distribution-agent:3.0.1

ENV JDK11=/opt/java/openjdk-11
COPY --from=openjdk11 /usr/lib/jvm/jdk ${JDK11}

# Switch to root user for installing packages
USER root

# Install additional packages
ENV DEBIAN_FRONTEND noninteractive
RUN apt update \
 && apt install --assume-yes --no-install-recommends zip unzip

# Switch back to application user
USER gradle

Appendix F: Dealing with tests that start Docker containers

Developers nowadays rely on Docker containers being started from inside their tests in order to test integration with external services. Frameworks like Testcontainers provide Java APIs that make this even easier. Depending on the deployment model you chose, you need to take different steps in order to support executing Docker-based tests on Test Distribution agents.

In case you decided to deploy the JAR directly you need to make sure that:

  • Docker is installed on the host executing the agent application.

  • The user executing the agent application has sufficient permissions to use Docker.

In case you decided for a Docker-based deployment you need to make Docker available inside the Test Distribution agent Docker container. The Testcontainers documentation provides more information about patterns that can be used to do this.

Appendix G: Verifying the signature of the agent jar

(agent 1.0.1+)

The agent jar is published to alongside its signature. The public key is published to You can verify the signature as follows:

$ curl -OL && \
  curl -OL && \
  gpg --keyserver --recv-key 7B79ADD11F8A779FE90FD3D0893A028475557671  && \
  gpg --verify develocity-test-distribution-agent-3.0.1.jar.asc develocity-test-distribution-agent-3.0.1.jar

The output of the last command should look similar to the following:

gpg: Signature made Thu Sep 28 16:17:46 2023 CEST
gpg:                using RSA key 893A028475557671
gpg: Good signature from "Gradle Inc. <>" [unknown]
gpg:                 aka "Gradle Inc. <>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 7B79 ADD1 1F8A 779F E90F  D3D0 893A 0284 7555 7671

This verifies that the artifact was signed with the private key that corresponds to the imported public key. The warning is emitted because you haven’t explicitly trusted the imported key (hence [unknown]). One way of establishing trust is to verify the fingerprint over a secure channel. Please contact technical support should you wish to do so.