Common Deployment Errors

Unknown Technology

When pushing your app to Scalingo, you might get the following error:

<-- Start deployment of [my-app] -->
 !     We didn't find the type of technology your are using...
       We're sorry this build is failing!

       Refer to the documentation to find out why:

       If you can't find the issue in your application,
       please send us an email at

 !   Error deploying the application
 !   → Invalid return code from buildpack

There are two main solutions to this problem.

Project in a Subdirectory

It may happen that your project is in a subfolder of your Git repository. It’s completely OK but remind that Scalingo’s deployment system looks at the root of the Git repository by default.

You need to setup the PROJECT_DIR environment variable for your application, and our build system will automatically look at it. The variable has to target a valid directory, otherwise the deployment process will fail.


If your project has the following architecture:


You want to deploy what is in the /server directory, so you have to define PROJECT_DIR=server. That’s it! It will be taken into account at your next deployment.

Technology Detection

To detect the technology used by your application, we iterate over the technologies alphabetically. It means that if your project contains multiple technologies, we will pick the first one detected.

If you want to skip the detection phase and force the use of a specific buildpack, add the environment variable BUILDPACK_NAME to your project.

If you need to use multiple technologies, you can use the multi-buildpacks.

You can also develop your own buildpack and add the environment variable BUILDPACK_URL to have complete control on the detection and build phases.

More information is available on buildpacks or multi-buildpacks.

Here is how we detect your technology:


A Gemfile should be present at the root of your repository.


The file package.json should be present at the root of the project.


The directory .meteor should be present at the root of your project.


You need to have either an index.php file or both composer.json and composer.lock files at the root of your project.


The file Pipfile, requirements.txt or must be present at the root of your project.


The file pom.xml should be present at the root of your project.


You need to have at least an *.sbt file or a project/*.scala/.sbt/*.scala file or a project/ file.


The file grails-app must be at the root of your project.


The file project.clj must be at the root of your project.


You need to have at least one *.go file at the root of your project. Then, we detect the Go language and install any dependency with your Godeps directory (see more about Godeps).

Git Submodule

If your project repository uses Git submodules, please be aware that Scalingo will not pull them. This Git feature is not supported on the platform for different reasons. The main reason being that we currently have no way to authenticate the git pull operation to a private Git repository when doing the deployment. Actually Git submodules are often considered as a broken feature of Git, that is why we do not encourage its usage or support it today.

We recommend you to vendor a specific release of the code of the sub-git repository in your main repository before pushing.

Build Errors

When your application is deployed, the dependencies are gathered and are packaged into an application image

Invalid Return Code From Buildpack

Your application image is built using a buildpack (List of buildpacks). If the buildpack exits with an error, it is probably linked to your project. You should be able to see the content of the error in your console. Then adapt your code according to it.

If you think the error comes from our buildpacks, feel free to contact us and we will fix it as soon as we can.

Image Too Large

The maximal size of an application image is 1.5 GiB. If your assets, your dependencies and the code of your application weigh more than this limit, different solutions are available to lighten the image of your application:

  • Try to remove unused external dependencies or assets.
  • Define a .slugignore file to exclude files from the image.

If you absolutely need all these data, please contact us at

Start Errors

After creating the container image of your application, it is deployed in our infrastructure. The following errors may happen if your application is not configured correctly.

If something wrong happens, you should first look at the logs of your app. In most cases, all the information you need is displayed here.

Boot Timeout

When started on our servers, your application has 60 seconds to bind the port defined by the environment variable PORT. After this delay, we consider that your application is not able to boot and this error happens.

Common causes

  • The server is not listening on the port defined by the environment variable PORT. Then your application is running correctly but it is not reachable. The application must also listen on and not

Crash of the Application

When your application starts, it may stop unexpectedly for various reasons related to your project.

Common causes

  • Syntax error and import error in your code. Make sure that your project is working correctly locally before deploying it on our platform. If it doesn’t, it won’t be better here.
  • The database link is badly configured. If you are using our built-in database addons, we create an environment variable with a name following this scheme: SCALINGO_{DB_TYPE}_URL. Your application must use this value or you can rename it to fit your needs.
  • The way your application is starting is incorrect and it results in a crash. To define or change how your application is started by the platform, use the Procfile file.

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Common Deployment Errors

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