GitHub user agoodm opened a pull request: https://github.com/apache/zeppelin/pull/1439
[ZEPPELIN-1423] Allow users to specify pre/post-execute callbacks for interpreters ### What is this PR for? One feature built-in to Jupyter's ipykernel that is currently missing in Zeppelin are pre/post-execute "callbacks". This PR allows for the possibility of entering code that is set to be executed by the interpreter before the code entered into the paragraph (pre-execute) and after (post-execute). In addition to saving some users the effort of writing code that they want executed in every paragraph, this will help pave the way for more advanced features coming soon, like automatically displaying matplotlib figures without an explicit call to a `show()` function. See the JIRA issue for more details on this. The core implementation for this is primarily contained in a new class called `InterpreterCallbackRegistry` which heavily mimics the Angular Display system (eg, `AngularObjectRegistry`). While this interface alone should suffice for Interpreter maintainers on the Java/JVM side, I also thought it might be useful to expose the system directly to the users in their notebooks. Hence, an implementation that works with the spark and pyspark interpreters (via the `ZeppelinContext` class) is also included here. ### What type of PR is it? New Feature ### Todos * [ ] - Add unit tests * [ ] - Add new documentation * [ ] - Find a better way to check for errors in pre-execute as this can brick the REPL (see more info below) ### What is the Jira issue? [ZEPPELIN-1423](https://issues.apache.org/jira/browse/ZEPPELIN-1423) ### How should this be tested? In a new note, add the following lines of code to a paragraph: ```python %pyspark z.registerCallback("post_exec", "print 'This code should be executed before the parapgraph code!'") z.registerCallback("pre_exec", "print 'This code should be executed after the paragraph code!'") ``` Then run any other paragraph in the note containing some other code, eg ```python %pyspark print "This code should be entered into the paragraph by the user!" ``` The output should be: ``` This code should be executed after the paragraph code! This code should be entered into the paragraph by the user! This code should be executed before the parapgraph code! ``` You should also test out the other two methods (`getCallback()` and `unregisterCallback()`) specified in `ZeppelinContext.java`. One final caveat that should be mentioned: If there are errors in the code you specify for a pre-execute event, it will render the interpreter useless since the current implementation prepends the the code specified in `pre_exec` directly to the paragraph entered code before calling `interpret()`. The current workaround for this would be to either restart the interpreter group or call `unregisterCallback()` via a different REPL within the interpreter group (eg, `z.unregisterCallback("pyspark", "pre_exec")` from the spark interpreter). I would appreciate if anyone here would be willing to share any better approaches here. ### Questions: * Does the licenses files need update? No * Is there breaking changes for older versions? No * Does this needs documentation? Yes You can merge this pull request into a Git repository by running: $ git pull https://github.com/agoodm/zeppelin ZEPPELIN-1423 Alternatively you can review and apply these changes as the patch at: https://github.com/apache/zeppelin/pull/1439.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #1439 ---- commit 2c4756d4d6861ba6192e52f0ca1c4c23b21a8070 Author: Alex Goodman <ago...@users.noreply.github.com> Date: 2016-09-13T20:32:36Z First attempt at adding pre/post-execute callbacks Added support for pre/post-execute callback hooks to interpreters commit e4e4ef3d8b4e3da1937d43892e88f030a7bd42b7 Author: Alex Goodman <ago...@users.noreply.github.com> Date: 2016-09-19T22:48:34Z Added support for user defined callbacks in spark/pyspark interpreters ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. ---