Continuing a Cylc 7 Workflow with Cylc 8
Does This Change Affect Me?
Read this if you have a partially complete Cylc 7 workflow that you want to continue, rather than start from scratch, with Cylc 8. Some cycling workflows, for example, may need to run expensive “cold start” tasks and incur a multi-cycle spin-up if started from scratch.
Cylc 8 cannot restart a Cylc 7 workflow in-place, and continuing in a new run directory involves some careful set up (below). So, if possible you should complete the run with Cylc 7.
To continue a Cylc 7 workflow with Cylc 8:
Stop the Cylc 7 workflow at an convenient place
Typically the end of a cycle point, to simplify the continuation
Install a new instance of the workflow from source, with Cylc 8
Adapt file paths to the new run directory structure, in workflow and task configurations
Note Cylc 8 does remote file installation when a job is first submitted to a platform
Copy runtime files needed by upcoming tasks from the old to the new run directory
This could include external files installed by initial tasks at runtime
Note different files could be present on different job platforms
Start the new Cylc 8 run at the appropriate cycle point or task(s) in the graph
Don’t reset the initial cycle point (in the
flow.cylcor on the command line) to the start point of the Cylc 8 run. That would result in the “cold start” that this continuation procedure is designed to avoid. Instead use the
cylc play, to start at the right place within the graph.