Evergreen Aware Git Bisect

TLDR

bisect will print the last known passing version and first known failing version of mongo for a --branch, --variant and --lookback period, with respect to a user provided shell --script.

Usage

bisect can be invoked from within the mongo repo like so:

buildscripts/resmoke.py bisect
  --branch   ["master", "v5.1", "v5.0", etc.]
  --variant  ["enterprise-rhel-80-64-bit-dynamic-required", "ubuntu1804-debug-asan", etc.]
  --lookback [30, 90, 180, etc]
  --script    [shell script to indicate presence of bug]
  --python-installation [(optional) path to python3.7+]

To use this command, all that is needed is to write the shell --script which runs against a mongo version and returns 0 upon successful execution. The --script will be run from within the build/resmoke-bisect directory described below.

Bisect

All versions for the given --branch, --variant and --lookback period are fetched from Evergreen.

The repo, binaries, artifacts and virtual environment are downloaded to the build/resmoke-bisect directory for the middle version. This is what the build/resmoke-bisect directory may look like — where mongo_repo is the github repo and bisect_venv is the virtual environment:

bisect_venv		mongo_repo		mongobridge		mongod			mongokerberos		
mongoqd			mongotmock		wt                      mongo			mongoauditdecrypt	
mongocryptd		mongodecrypt		mongoldap		mongos			mqlrun

The --script is run from within this build/resmoke-bisect directory. If it completes successfully, bisect continues on newer versions. Else, if it fails, bisect continues on older versions. This is repeated until the algorithm completes.

The last known passing version and first known failing version print to stdout

Notes

1. This bisect command assumes a perfect partition between passing & failing versions. ie: [Pass, Pass, Pass, Fail, Fail, Fail]. If there is not a perfect partition, this command will not work as expected. If there is not a perfect partition, try modifying the --lookback period or shell --script.

2. Bisecting to beyond a year may not be supported since Evergreen artifacts are only stored for a year.

3. Older versions will have different syntax, so you may need to run resmoke.py instead of resmoke.py run if the latter fails in the shell script.

Help

buildscripts/resmoke.py bisect --help