[SDKs] Refactor run-command so it can be used as an SDK by scripts in a git tree
- Put the program you need in a docker image. Use run-command from the arvados tree to wrap it as a crunch job.
- Write a native crunch script in your git tree.
The first option forces you to save a new docker image in order to run a new version of your program. Unacceptable!There are several features of run-command that make it convenient and attractive to beginners. However, it forces you to use a totally different approach to developing and running scripts, an approach which prevents you from doing some important things:
- Keeping your code in revision control,
- Using the same code in more than one pipeline template,
- Writing jobs in the programming language of your choice.
There is no migration path from a simple run-command job to a non-trivial program, so the developer is forced to choose: live with run-command's custom JSON-based programming language, or abandon the existing pipelines and all of run-command's advantages, and rewrite everything in a normal language like Python.This can be addressed by refactoring run-command as a set of utilities and features, rather than a programming language that can only be used inside crunch jobs.
- The "run-command language" interpreter should be runnable like other interpreters (
- Convenience features like "store output dir contents in Keep and set success=true at end of task" should be ported to other SDKs too (most obviously bash), so authors can migrate from the JSON language to a normal language.
- It should be possible to provide a crunch script in any language by copying the script itself into the job record. (This makes it possible to run jobs without touching git.)
- The whole point of the run-command language is to already be JSON-encoded, which means it should be provided in a serialized attribute like script_parameters. (Other languages are just text, but that can also fit in a serialized field.)
- The name of the "script" attribute already suggests that you can put a script in it. This could change type (from varchar(255) to text) and become a serialized field capable of containing a string or a hash. This means we can't rely on "script" to be a short name suitable for displaying in UI (a problem we already have with run-command jobs: the program has no name, so we display the name of the language instead).
- We could support passing the name of an interpreter in "script" (e.g., "run-command" or "python") and passing the program itself in
script_parameters[stdin]. We would have to treat string and hash/array cases differently: if stdin is a string, pass the string value, but if stdin is a hash or array, pass its JSON encoding.
- It should be possible to move your run-command program into a git tree and run it from there.
- Currently, this can be done awkwardly by copying some version of run-command into your own git tree.
- With #4027, we can make run-command's features available through the SDK.
- Then we just need
#!whatever-the-language-is-calledto work, or some other way to invoke run-command from the installed SDK, rather than requiring it to be in
#2 Updated by Tom Clegg about 5 years ago
- Subject changed from [Crunch] Support using run-command to wrap a script in a separate git tree. to [SDKs] Refactor run-command so it can be used as an SDK by scripts in a git tree
- Description updated (diff)
- Category changed from Crunch to SDKs
- Target version set to Arvados Future Sprints
- Story points changed from 1.0 to 2.0
#5 Updated by Peter Amstutz about 5 years ago
(comments from IRC)
Now that we have the "deploy SDK into container" feature, moving most of run-command's functionality into the SDK is a good idea. The main reason I didn't do that was because the deployment cycle for the SDK was much less convenient than for a crunch script. In the long term I'd prefer to deprecate run-command in favor of CWL (and send run-command to the scrapyard for spare parts).