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Docker Building Guidelines

While creating a docker to execute on Polly, the following must be taken into consideration:

  • Docker location: Dockers must be present in either Docker Hub or Amazon ECR.

    • Soon, You will be able to have Dockers directly on Polly.
  • Docker Requirement: Only self contained dockers can be run on Polly. A self contained docker is one which has the code to get input files as well as upload output files back contained in the docker.

  • Public and Private Dockers: Public as well as private dockers are supported. In order to run private dockers, “secret” should be passed as a key in the JSON file. If your private dockers are on Polly itself, you don't require to generate this secret.

  • Secret Key for Private Docker: To get the secret key for the private docker, the following steps need to be followed:

    • For MacOS,

      • You need to remove the key value pair "credsStore": "osxkeychain" from the config.json file present in the directory /Users/< username >/.docker.

      • You need to be logged in to DockerHub or ECR through the terminal. If not, you will need to log in.

      • Run the command sudo polly on the terminal.

      • Select the option miscellaneous followed by create secret for docker.

      • Provide the path to the docker config file (the usual path for docker config is /Users/< username >/.docker/config.json in Mac and /home/< username >/.docker/config.json in Linux). Relative paths are not supported.

      • Select the account in which the docker to be run is present.

      • Copy the long text string (secret key) output to the JSON file in the key “secret”.

  "machineType": "gp",
  "image": "docker/whalesay",
  "tag": "latest",
  "Secret": "ewoAImF1dVnphR0ZzWjNWd2RHRTZSVkJKUXlOcFlXMGsiCgkw==",
  "name": "exampleName",
  "command": [
      "cowsay","hello world"
  • Passing Environment variables: Two types of Environment variables can be passed in the json file.

    • Normal environment variables are saved in a database for future references. These can be passed in the parameter "env” in the json file.

    • Private environment variables are not saved in any database. These can be used for passing credentials in the json file. These can be passed in the parameter “secret_env” in the json file.


  • The value of Environment variables should always be string. For example, the correct way to assign Environment variable is {“parallel_threads” : “2”} and NOT {“parallel_threads” : 2}.
 "machineType": "gp",
 "image": "your_docker",
 "tag": "latest",
 "env": {
   "ENV1": "ENV_VALUE1",
   "ENV2": "ENV_VALUE2"
 "secret_env": {
 "name": "docker running"
  • Here is an example gist showing how input data for a job can be taken from and output stored back to Polly Workspaces.

Polly CLI help

If help is needed for any command, just type --help at the end of the command and execute.

Polly CLI Help

Figure 13. Polly CLI Help