fix: don't hang when sharepolicies return immediately #74
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Problem: when using a SharePolicy (rather than doing some asynchronous work) it was possible for the repo to hang. The symptom of this would be that a repo would never respond to sync messages for a document when a SharePolicy returned a positive response for the document. Why was this happening? When the repo first receives a sync message for a (document, peer) combination it checks whether the SharePolicy allows synchronization with the peer in question. To do this the repo creates a new future (correspoinding to SharePolicy::should_sync) and then puts it in a list of share decisions to poll. The share decisions are then polled on the next run through the event loop. If the repo is in a very quiet loop then no new event occurs to trigger the first poll of the future. Solution: at the end of the repo event loop check if there are any share decisions to poll. If there are, then run the loop again.
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Problem: when using a SharePolicy (rather than doing some asynchronous work) it was possible for the repo to hang. The symptom of this would be that a repo would never respond to sync messages for a document when a SharePolicy returned a positive response for the document.
Why was this happening? When the repo first receives a sync message for a (document, peer) combination it checks whether the SharePolicy allows synchronization with the peer in question. To do this the repo creates a new future (correspoinding to SharePolicy::should_sync) and then puts it in a list of share decisions to poll. The share decisions are then polled on the next run through the event loop. If the repo is in a very quiet loop then no new event occurs to trigger the first poll of the future.
Solution: at the end of the repo event loop check if there are any share decisions to poll. If there are, then run the loop again.