4.3 Builds

A build is an execution of a build plan, which is either configured as a sequence of steps in a job, or submitted directly to Concourse as a one-off build via fly execute.

Containers and volumes are created as get steps, put steps, and task steps run. When a build completes successfully, these containers go away.

A failed build's containers and volumes are kept around so that you can debug the build via fly intercept. If the build belongs to a job, the containers will go away when the next build starts. If the build is a one-off, its containers will be removed immediately, so make sure you intercept while it's running if you want to debug.

4.3.1 fly builds

To list the most recent builds, run:

$ fly -t example builds

To list the builds of a job, run:

$ fly -t example builds -j pipeline-name/job-name

This can be useful for periodically monitoring the state of a job. The output also works well with tools like awk and grep.

By default the most recent 50 builds are shown. To see more builds, use the -c flag, like so:

$ fly -t example builds -c 100

4.3.2 fly intercept

Sometimes it's helpful to be on the same machine as your tasks so that you can profile or inspect them as they run or see the state the machine at the end of a run. Due to Concourse running tasks in containers on remote machines this would typically be hard to access.

To this end, there is a fly intercept command that will give you an interactive shell inside the specified container. Containers are identified by a few things, so you may need to specify a few flags to hone down the results. If there are multiple containers that the flags could refer to, an interactive prompt will show up allowing you to disambiguate.

The command fly hijack is an alias of fly intercept. Both can be used interchangably.

For example, running the following will run a task and then enter the finished task's container:

$ fly -t example execute
$ fly -t example intercept --step build

When intercepting a job running on a windows worker, you will need to specifically tell fly to target PowerShell as an additional argument:

$ fly -t example intercept powershell

Containers are around for a short time after a build finishes in order to allow people to intercept them.

You can also intercept builds that were run in your pipeline. By using --job, --build, and --step you can intercept a specific step from a build of a job in your pipeline. These flags also have short forms, like so:

$ fly -t example intercept -j some-pipeline/some-job -b some-build -s some-step

Be warned, if more than one person is using a Concourse server for running one-off builds then you may end up in a build that you did not expect!

Note that --build can be omitted, and will default to the most recent build of the job. One-off builds can be reached by passing in their build ID to --build which can be found on the build list page.

The --step flag can also be omitted; this will let you pick the step interactively if you don't know the exact name.

Resource checking containers can also be intercepted with --check or -c:

$ fly -t example intercept --check some-pipeline/some-resource

A specific command can also be given, e.g. fly intercept ps auxf or fly intercept htop. This allows for patterns such as watch fly intercept ps auxf, which will continuously show the process tree of the current build's task, even as the "current build" changes.

The working directory and any relevant environment variables (e.g. those having come from params) used by the original process will also be used for the process run by intercept.

4.3.3 fly abort-build

To abort a build of a job, run:

$ fly -t example abort-build --job my-pipeline/my-job --build 3

This will cancel build 3 of the my-job job in the my-pipeline pipeline.

4.3.4 fly watch

Concourse emits streaming colored logs on the website but it can be helpful to have the logs availiable to the command line. (e.g. so that they can be processed by other commands).

The watch command can be used to do just this. You can also view builds that are running in your pipeline, or builds that have already finished.

Note that unlike fly execute, killing fly watch via SIGINT or SIGTERM will not abort the build.

To watch the most recent one-off build, just run fly watch with no arguments. To watch a specific build (one-off or no), pass --build with the ID of the build to watch. This ID is available at the start of fly execute's output or by browsing to the builds list in the web UI.

By using the --job and --build flags you can pick out a specific build of a job to watch. For example, the following command will either show the archived logs for an old build if it has finished running or it will stream the current logs if the build is still in progress.

$ fly -t example watch --job my-pipeline/tests --build 52

If the --job flag is specified and --build is omitted, the most recent build of the specified job will be selected.