Page Comparison

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SBOI lock = "/SBOI/" + runnable.getComponentName();

example: /SBOI/SampleComponent

batch lock = "/"+runnable.getComponentName() + "/B" + batch.getBatchID() + "-RT" + batch.getRoundTripNumber();

example: /SampleComponent/B400022028241-RT1

Why?

An autonomous components will be able to "poll" the Summa Newspaper Batch Object IndexEvent Framework for events that have happened. The component will know which events should have occurred for a batch before I can start processing the batch. Also which events should have occurred and failed, and which events should not have occurred. The component also needs to know which batches it is currently working on itself. This is what the zookeeper tracks the locks for.

Autonomous component locking

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procedure 

Each of the autonomous components will exist as cron jobs. Periodically, often every minute or thereabouts, the cron job will activate. It will then follow the procedure below. Each autonomous component will have a field called "simultaneousProcesses", which indicate how many children it can spawn.

1. Lock "SBOI+component name"
2. query SBOI for batches
3. For each returned batchLock "
   1. Attempt to lock the "batch+component name"
   2. if successful, break loop
4. unlock "SBOI+component name"
5. Do work on locked batch (if any)
6. store results in DOMS
7. unlock "batch+component name"

Autonomous component locking procedure 2

Each of the autonomous components will exist as cron jobs. Periodically, often every minute or thereabouts, the cron job will activate. It will then follow the procedure below.

1. 1. Create child until number of children == "simultaneousProcesses"
2. unlock "SBOI+component name"
3. query SBOI for batches
4. For each returned batch
5. Attempt to lock the "batch+component name"
6. Do work on locked batch (if any). Possibly spawn sub process
7. store results in DOMS
Start each child
8. Wait for all children to complete their work
9. unlock "batch+component name"
10. unlock "SBOI+component name"

Which one will we use?

Method 1 is simpler to implement (and already done). Method 1 will only maintain a very shortlived lock on SBOI. To run method 1 on three batches, just start it three times.

Method 2 is conceptually simpler to understand. It allows for developer controlled degree of parallelism, but will also force us to code this ourselves.  This is the method described on the Autonomous Components page. Well actually the description is this:

If the robot finds that a batch is ready to work on, it starts working on this batch. The robot will not poll for more work while working.

Some of the robots will be able to multitask, and others will not. Multitasking is done in a slightly different way for robots than for humans. The multitasking robot will build a new little non-multitasking robot child, give him the batch to work on, and then go back to sleep. Next time it polls for work, it will have to remember not the start work on batches that already have been assigned to any of the robots children. This also means that there must only ever be one instance of each type of multitasking robot running.

When a robot have finished work on a batch, it must record this, so the assembly line can move forward. It records the event Batch Object, stored in the Digital Object Management System, DOMS, system, in the form of an event somewhat like "I, <ROBOT>, did this <THIS WORK> on batch <ID> with <THIS RESULT>". The SBOI will then periodically (often) query DOMS for updates to the Batch objects. When the SBOI discover a batch object update, it updates the index, so that robots further along the assembly line can work on the batch.

 Each child will do the work described and store the result back into DOMS.

The autonomous component will, as described above, NOT finish before all spawned children have finished. It is the responsibility of the cron system to not start the autonomous component before the previous invocation have finished