(4/6) Implement proper remove-before-add behavior in P2PDataStorage #3638
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Instead of using a subclass that overwrites a value, utilize Guice to inject the real value of 10000 in the app and let the tests overwrite it with their own.
Remove unused imports and clean up some access modifiers now that the final test structure is complete
Previously, this interface was called each time an item was changed. This required listeners to understand performance implications of multiple adds or removes in a short time span. Instead, give each listener the ability to process a list of added or removed entrys which can help them avoid performance issues. This patch is just a refactor. Each listener is called once for each ProtectedStorageEntry. Future patches will change this.
Minor performance overhead for constructing MapEntry and Collections of one element, but keeps the code cleaner and all removes can still use the same logic to remove from map, delete from data store, signal listeners, etc. The MapEntry type is used instead of Pair since it will require less operations when this is eventually used in the removeExpiredEntries path.
…batch All current users still call this one-at-a-time. But, it gives the ability for the expire code path to remove in a batch.
This will cause HashMapChangedListeners to receive just one onRemoved() call for the expire work instead of multiple onRemoved() calls for each item. This required a bit of updating for the remove validation in tests so that it correctly compares onRemoved with multiple items.
…ch removes bisq-network#3143 identified an issue that tempProposals listeners were being signaled once for each item that was removed during the P2PDataStore operation that expired old TempProposal objects. Some of the listeners are very expensive (ProposalListPresentation::updateLists()) which results in large UI performance issues. Now that the infrastructure is in place to receive updates from the P2PDataStore in a batch, the ProposalService can apply all of the removes received from the P2PDataStore at once. This results in only 1 onChanged() callback for each listener. The end result is that updateLists() is only called once and the performance problems are reduced. This removes the need for bisq-network#3148 and those interfaces will be removed in the next patch.
Now that the only user of this interface has been removed, go ahead and delete it. This is a partial revert of f5d75c4 that includes the code that was added into ProposalService that subscribed to the P2PDataStore.
Write a test that shows the incorrect behavior for bisq-network#3629, the hashmap is rebuilt from disk using the 20-byte key instead of the 32-byte key.
julianknutsen
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Addresses the first half of bisq-network#3629 by ensuring that the reconstructed HashMap always has the 32-byte key for each payload. It turns out, the TempProposalStore persists the ProtectedStorageEntrys on-disk as a List and doesn't persist the key at all. Then, on reconstruction, it creates the 20-byte key for its internal map. The fix is to update the TempProposalStore to use the 32-byte key instead. This means that all writes, reads, and reconstrution of the TempProposalStore uses the 32-byte key which matches perfectly with the in-memory map of the P2PDataStorage that expects 32-byte keys. Important to note that until all seednodes receive this update, nodes will continue to have both the 20-byte and 32-byte keys in their HashMap.
Addresses the second half of bisq-network#3629 by using the HashMap, not the protectedDataStore to generate the known keys in the requestData path. This won't have any bandwidth reduction until all seednodes have the update and only have the 32-byte key in their HashMap. fixes bisq-network#3629
The only user has been migrated to getMap(). Delete it so future development doesn't have the same 20-byte vs 32-byte key issue.
In order to implement remove-before-add behavior, we need a way to verify that the SequenceNumberMap was the only item updated.
It is possible to receive a RemoveData or RemoveMailboxData message before the relevant AddData, but the current code does not handle it. This results in internal state updates and signal handler's being called when an Add is received with a lower sequence number than a previously seen Remove. Minor test validation changes to allow tests to specify that only the SequenceNumberMap should be written during an operation.
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@chimp1984 What do you think about that? |
freimair
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Nov 21, 2019
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utAck
ad rebroadcasting even if not applicable: I had that feeling for a long time now. We have stale messages in the network. Thought about resending remove messages e.g. 3 times to spread the news even if a couple of clients missed the first one. Pretty much the same for every remove message. Since the seq number is touched, there is no risk of overloading the network.
my opinion: rebroadcast even if we did not yet receive the respective add. revert if something bad happens.
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I'll just make an additional PR that adds rebroadcasting in the remove-before-add case. It will involve a bit of validation work that will conflict with my patch stack so I won't be able to get it out until tomorrow. A different PR will also allow the approved patches to go in without forcing them back to stale. |
julianknutsen
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New commits are at 526aee5
According to the original design doc, removes-before-adds were expected and should have the behavior that a remove with a larger sequence number will block a future add with a lower sequence number.
The idea is that you don't want out of order remove messages to get lost otherwise you may do more work then necessary by adding a stale
ProtectedStorageEntrywhen you could have ignored it entirely. I'm not sure of any existing cases, but this may have been the cause of 'flapping' or 'undeleted' messages as nodes were starting.I've left the existing behavior w.r.t. broadcasting. Even if this
remove()is the first message we have seen for a payload, we don't rebroadcast it to our peers. I'm not exactly sure what we want here, but rebroadcasting, in this case, could help network propagation and we may want to adopt the invariant that ANY state updates caused by a message are worth of rebroadcasting because the same state updates may be relevant to our peers.