Lack of Output

A command will be killed if a certain period of time has passed with no output. By default, this is 10 minutes. This is designed to prevent errors in builds from hanging using a large number of credits unintentionally.

Disable Output Buffering

Some test runners and tools make use of what is known as output buffering. This is where the program will wait to output text in batches as opposed to line by line. Sometimes, all output will be buffered until the process exits. If a test or task requires more than 10 minutes and is buffering its output, this can cause CircleCI to kill the step as there has been no output during that time

In Python, this can be sometimes be disabled via the PYTHONUNBUFFERED environment variable. This can be set in a job step via export:

steps:
  - run:
      name: Run Tests
      command: |
        export PYTHONUNBUFFERED=1
        python -m unittest

Increase Context Deadline (Timeout)

If the task does not have a way to generate any output, the default context deadline can be increased:

steps:
 - run:
     name: Run Tests
     no_output_timeout: 30m
     command: python -m unittest

The job step can also timeout because there is an issue with the tests or task is actually hanging. Some examples of causes of this would be where a process is waiting for user input or a loop is polling a network resource that never comes available.

Additional Resources:

• Debug Ruby RSpec Test Timeout With No Output (exceeded 10m0s): context deadline exceeded
• MacOS Build Times Out With "Too long with no output"
• Rails DB Timeout Error: Too long with no output (exceeded 10m0s) when using set_config.