remote job submission: fix race condition

[davidpanderson]

Scenario:

• a submit_batch() creates a batch in INIT state
  and starts creating jobs
• while it's in progress, a query_batches() RPC enumerates batches
• while the query_batches() is in progress,
  the submit_batch() finishes and changes the state to IN_PROGRESS
• the query_batches() finishes and rewrites the batch in INIT state

Solution: query_batches() doesn't update batches in INIT state

Fixes #

Description of the Change

Alternate Designs

Release Notes

[lfield]

Is there any reason why the call is done the first place? The if statement could be changed to:

    if (BATCH_STATE_COMPLETE < $batch->state and  $batch->state < BATCH_STATE_COMPLETE) {

[davidpanderson]

? The function of the RPC is to find the status of batches.

[lfield]

I don’t mean the RPC call but the get_batch_params function.

[davidpanderson]

That function computes the batch's fraction done,
i.e. what fraction of its jobs have finished.

[lfield]

I understand but why call that function at all if the batch is not in the state BATCH_STATE_IN_PROGRESS. Why not do the following instead?

if ($batch->state == BATCH_STATE_IN_PROGRESS) {
$batch = get_batch_params($batch, $wus);
}

[lfield]

Sorry clicked on the wrong button.

[davidpanderson]

You could do it either way. This way is fine.

[lfield]

ok, I was just considering readability of the code by having the if before the function call verses the abstraction of having it contained with the function.