Today Recipe cooking is a client side logic. Recipe also supports extensions i.e. user can cook his/her own custom recipes.
Decision to make it client side logic was for the following reasons
- Keep it isolated from falcon server
- As custom recipe cooking is supported, user recipes can introduce security vulnerabilities and also can bring down the falcon server
Today, falcon provides HDFS DR recipe out of the box. There is a plan to add UI support for DR in Falcon.
Rest API support cannot be added for recipe as it is client side processing.
If the UI is pure java script[JS] then all the recipe cooking logic has to be repeated in JS. This is not a feasible solution - if more recipes are added say DR for hive, hbase and others, UI won't be extensible.
For the above mentioned reasons Recipe should me made a server side logic.
Provided/Trusted recipes [recipes provided out of the box] can run as Falcon process. Recipe cooking will be done in a new process if its custom recipe [user code].
For cooking of custom recipes, design proposed should consider handling security implications, handling the issues where the custom user code can bring down the Falcon server (trapping System.exit), handling class path isolation.
Also it shouldn't in anyway destabilize the Falcon system.
There are couple of approaches which was discussed
Custom Recipe cooking can be carried out separately in another Oozie WF, this will ensure isolation. Oozie already has the ability to schedule jobs as a user and handles all the security aspects of it.
- Provides isolation
- Piggyback on Oozie as it already provides the required functionality
- As recipe processing is done in different WF, from operations point of view user cannot figure out recipe processing status and thus adds to the operational pain. Operational issue with this approach is said to be the overall
apparatus needed to monitor and manage the recipe-cooking workflows.
Oozie scheduling can bring arbitrary delays Granted we can design around the limitations and make use of the strengths of the approach but it seems something we can avoid if we can.
- There has been few discussions to move away from Oozie as scheduling engine for Falcon. If this is the plan going forward its good not to add new functionality using oozie.
Custom recipe cooking is done on the server side in a separate independent process than Falcon process I.e. It runs in a different JVM. Throttling should be added for how many recipe cooking processes can be launched keeping in mind the machine configuration.
- Provides isolation as recipe cooking is done in a independent process
- Performance overhead as new process is launched for custom recipe cooking
- Adds more complexity to the system
This bug will be used to move recipe processing for trusted recipes to server side.