Eventual Visibility

[bbengfort]

The eventual nodes are not having writes that reach full visibility -- check the anti-entropy implementation, it should eventually converge!

[bbengfort]

Reimplement Push style anti-entropy as follows:

• Keep a cache or recent versions (locally written or received by anti-entropy)
• Send entire cache to receiving device to f other nodes every anti-entropy delay
• Keep version in cache for TTL amount
• Append past versions behind the current latest version.

NOTE: could cause duplication if an anti-entropy message is received from a write already in log but one that has expired via the TTL.

New parameters are:

• Anti-Entropy Delay: The interval/delay between anti-entropy sessions; should be based on the network latency or environment. Our current method use the T parameter: T/4. The delay can also be a uniform random number rather than a constant.
• num_neighbors: The number of neighbors to select in an anti-entropy session.
• Neighbor Selection: Whether or not a uniform random selection of neighbors is used or if selection is weighted by region or by success rate.
• TTL: In push based mechanism what is the TTL of spreading a particular version?

[bbengfort]

Ok, so the current mechanism is as follows:

Wait for anti-entropy delay milliseconds and then:

• Pick n neighbors (n=1 by default) and for every object in the log send the latest version.
• Recipient compares remote versions to local and writes higher version.
• Recipient sends back any locally later versions.