public static bool HappensAfter(VectorClock first, VectorClock second)
{
// Create immutable other to protect from concurrent accesses
ImmutableVectorClock immutableFirst = first.ToImmutable();
ImmutableVectorClock immutableSecond = second.ToImmutable();
// Get all possible ids
ImmutableHashSet <string> firstIds = immutableFirst.Ids;
ImmutableHashSet <string> secondIds = immutableSecond.Ids;
HashSet <string> allIds = new HashSet <string>(firstIds);
allIds.UnionWith(secondIds);
// For all ids, at least one has to be greater than
// other and none can be less
bool oneGreater = false;
foreach (string id in allIds)
{
int firstClock = immutableFirst[id];
int secondClock = immutableSecond[id];
if (firstClock > secondClock)
{
oneGreater = true;
}
else if (firstClock < secondClock)
{
return(false);
}
}
return(oneGreater);
}
public void Merge(VectorClock other)
{
// Create immutable other to protect from concurrent accesses
ImmutableVectorClock immutableOther = other.ToImmutable();
ImmutableHashSet <string> secondIds = immutableOther.Ids;
// Dont let concurrent updates while merging
lock (this) {
// Get all possible ids
HashSet <string> allIds = new HashSet <string>(vc.Keys);
allIds.UnionWith(secondIds);
foreach (string id in allIds)
{
int otherClock = immutableOther[id];
// Add other value if not there or
// update with max between both values
vc.AddOrUpdate(id, otherClock, (key, prev) => Math.Max(prev, otherClock));
}
// Invalidate immutable this
immutableThis = null;
}
}
public void Increment(string serverId)
{
lock (this) {
vc.AddOrUpdate(serverId, 1, (key, prev) => prev + 1);
// Invalidate immutable this
immutableThis = null;
}
}
private VectorClock BuildGrpcClock(CausalConsistency.ImmutableVectorClock vectorClock)
{
(IList <string> serverIds, IList <int> clocks) =
CausalConsistency.VectorClocks.ToIdsAndClocksList(vectorClock);
return(new VectorClock {
ServerIds = { serverIds },
ServerClocks = { clocks }
});
}
public override async Task <WriteResponse> Write(WriteRequest request, ServerCallContext context)
{
CausalConsistency.ImmutableVectorClock timestamp =
await dispatcher.OnWrite(ParseWriteRequest(request));
return(new WriteResponse {
Timestamp = BuildGrpcClock(timestamp)
});
}
public override ImmutableVectorClock ToImmutable()
{
lock (this) {
if (immutableThis == null)
{
immutableThis = ImmutableVectorClock.CopyOf(this);
}
}
return(immutableThis);
}
public static (IList <string>, IList <int>) ToIdsAndClocksList(
ImmutableVectorClock vectorClock)
{
IList <string> serverIds = new List <string>();
IList <int> clocks = new List <int>();
foreach ((string serverId, int serverClock) in vectorClock.Clocks)
{
serverIds.Add(serverId);
clocks.Add(serverClock);
}
return(serverIds, clocks);
}
public static ImmutableVectorClock FromIdsAndClocksList(
IList <string> serverIds,
IList <int> serverClocks)
{
IList <KeyValuePair <string, int> > clocks = new List <KeyValuePair <string, int> >();
for (int i = 0; i < serverIds.Count; i++)
{
clocks.Add(new KeyValuePair <string, int>(
serverIds[i],
serverClocks[i]
));
}
return(ImmutableVectorClock.FromClocks(clocks));
}
public CausalConsistency.ImmutableVectorClock Write(
string partitionId,
string objectId,
string value,
CausalConsistency.ImmutableVectorClock timestamp)
{
WriteRequest request = new WriteRequest {
PartitionId = partitionId,
ObjectId = objectId,
ObjectValue = value,
Timestamp = BuildGrpcClock(timestamp)
};
WriteResponse response = client.Write(
request,
deadline: DateTime.UtcNow.AddSeconds(60));
return(BuildVectorClock(response.Timestamp));
}
public CausalConsistency.ImmutableVectorClock Read(
string partitionId,
string objectId,
out string value,
CausalConsistency.ImmutableVectorClock timestamp)
{
ReadRequest request = new ReadRequest {
PartitionId = partitionId,
ObjectId = objectId,
Timestamp = BuildGrpcClock(timestamp)
};
ReadResponse response = client.Read(
request,
deadline: DateTime.UtcNow.AddSeconds(60));
value = !response.Missing ? response.ObjectValue : null;
return(BuildVectorClock(response.Timestamp));
}
public async Task BroadcastWrite(
string partitionId,
Broadcast.MessageId messageId,
string key,
string value,
CausalConsistency.ImmutableVectorClock replicaTimestamp,
string writeServerId,
long timeout)
{
await client.BroadcastWriteAsync(
new BroadcastWriteRequest {
PartitionId = partitionId,
MessageId = BuildMessageId(messageId),
Key = key,
Value = value,
ReplicaTimestamp = BuildClock(replicaTimestamp),
WriteServerId = writeServerId
},
deadline : DateTime.UtcNow.AddMilliseconds(timeout));
}
public static bool Equal(VectorClock first, VectorClock second)
{
// Create immutable other to protect from concurrent accesses
ImmutableVectorClock immutableFirst = first.ToImmutable();
ImmutableVectorClock immutableSecond = second.ToImmutable();
// Get all possible ids
ImmutableHashSet <string> firstIds = immutableFirst.Ids;
ImmutableHashSet <string> secondIds = immutableSecond.Ids;
if (firstIds.Count != secondIds.Count)
{
return(false);
}
foreach (string id in firstIds)
{
if (immutableFirst[id] != immutableSecond[id])
{
return(false);
}
}
return(true);
}
