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Cluster Keyspace Notification Support #813

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Cluster Keyspace Notification Support #813

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2 changes: 2 additions & 0 deletions StackExchange.Redis/StackExchange/Redis/RedisChannel.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ public struct RedisChannel : IEquatable<RedisChannel>

internal readonly byte[] Value;
internal readonly bool IsPatternBased;
internal readonly bool IsKeyspaceChannel;

/// <summary>
/// Indicates whether the channel-name is either null or a zero-length value
Expand All @@ -38,6 +39,7 @@ private RedisChannel(byte[] value, bool isPatternBased)
{
Value = value;
IsPatternBased = isPatternBased;
IsKeyspaceChannel = value != null && Encoding.UTF8.GetString(value).ToLower().StartsWith("__key");
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Instead of creating a byte[] for each comparison - it'd be far cheaper to pre-compute the byte array of "__key" once in a static and compare them instead :)

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Here is the fixed version.
https://pastebin.com/Q9T0Q99K

}

private static bool DeterminePatternBased(byte[] value, PatternMode mode)
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72 changes: 60 additions & 12 deletions StackExchange.Redis/StackExchange/Redis/RedisSubscriber.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
Expand Down Expand Up @@ -144,7 +145,7 @@ internal long ValidateSubscriptions()
private sealed class Subscription
{
private Action<RedisChannel, RedisValue> handler;
private ServerEndPoint owner;
private List<ServerEndPoint> owners = new List<ServerEndPoint>();

public Subscription(Action<RedisChannel, RedisValue> value) => handler = value;

Expand All @@ -170,33 +171,81 @@ public bool Remove(Action<RedisChannel, RedisValue> value)
}

public Task SubscribeToServer(ConnectionMultiplexer multiplexer, RedisChannel channel, CommandFlags flags, object asyncState, bool internalCall)
{
// subscribe to all masters in cluster for keyspace/keyevent notifications
if (channel.IsKeyspaceChannel) {
return SubscribeToMasters(multiplexer, channel, flags, asyncState, internalCall);
}
return SubscribeToSingleServer(multiplexer, channel, flags, asyncState, internalCall);
}

private Task SubscribeToSingleServer(ConnectionMultiplexer multiplexer, RedisChannel channel, CommandFlags flags, object asyncState, bool internalCall)
{
var cmd = channel.IsPatternBased ? RedisCommand.PSUBSCRIBE : RedisCommand.SUBSCRIBE;
var selected = multiplexer.SelectServer(-1, cmd, flags, default(RedisKey));

if (selected == null || Interlocked.CompareExchange(ref owner, selected, null) != null) return null;
lock (owners)
{
if (selected == null || owners.Contains(selected)) return null;
owners.Add(selected);
}

var msg = Message.Create(-1, flags, cmd, channel);

if (internalCall) msg.SetInternalCall();
return selected.QueueDirectAsync(msg, ResultProcessor.TrackSubscriptions, asyncState);
}

private Task SubscribeToMasters(ConnectionMultiplexer multiplexer, RedisChannel channel, CommandFlags flags, object asyncState, bool internalCall)
{
List<Task> subscribeTasks = new List<Task>();
var cmd = channel.IsPatternBased ? RedisCommand.PSUBSCRIBE : RedisCommand.SUBSCRIBE;
var masters = multiplexer.GetServerSnapshot().Where(s => !s.IsSlave && s.EndPoint.Equals(s.ClusterConfiguration.Origin));

lock (owners)
{
foreach (var master in masters)
{
if (owners.Contains(master)) continue;
owners.Add(master);
var msg = Message.Create(-1, flags, cmd, channel);
if (internalCall) msg.SetInternalCall();
subscribeTasks.Add(master.QueueDirectAsync(msg, ResultProcessor.TrackSubscriptions, asyncState));
}
}

return Task.WhenAll(subscribeTasks);
}

public Task UnsubscribeFromServer(RedisChannel channel, CommandFlags flags, object asyncState, bool internalCall)
{
var oldOwner = Interlocked.Exchange(ref owner, null);
if (oldOwner == null) return null;
if (owners.Count == 0) return null;

List<Task> queuedTasks = new List<Task>();
var cmd = channel.IsPatternBased ? RedisCommand.PUNSUBSCRIBE : RedisCommand.UNSUBSCRIBE;
var msg = Message.Create(-1, flags, cmd, channel);
if (internalCall) msg.SetInternalCall();
return oldOwner.QueueDirectAsync(msg, ResultProcessor.TrackSubscriptions, asyncState);
foreach (var owner in owners)
queuedTasks.Add(owner.QueueDirectAsync(msg, ResultProcessor.TrackSubscriptions, asyncState));
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owners isn't locked here, so this can go boom under load. The previous interlock above prevented this scenario.

owners.Clear();
return Task.WhenAll(queuedTasks.ToArray());
}

internal ServerEndPoint GetOwner() => Interlocked.CompareExchange(ref owner, null, null);
internal ServerEndPoint GetOwner()
{
var owner = owners?[0]; // we subscribe to arbitrary server, so why not return one
return Interlocked.CompareExchange(ref owner, null, null);
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This doesn't make sense anymore...would need to lock owners here instead.

}

internal void Resubscribe(RedisChannel channel, ServerEndPoint server)
{
if (server != null && Interlocked.CompareExchange(ref owner, server, server) == server)
bool hasOwner;

lock (owners)
{
hasOwner = owners.Contains(server);
}

if (server != null && hasOwner)
{
var cmd = channel.IsPatternBased ? RedisCommand.PSUBSCRIBE : RedisCommand.SUBSCRIBE;
var msg = Message.Create(-1, CommandFlags.FireAndForget, cmd, channel);
Expand All @@ -208,16 +257,15 @@ internal void Resubscribe(RedisChannel channel, ServerEndPoint server)
internal bool Validate(ConnectionMultiplexer multiplexer, RedisChannel channel)
{
bool changed = false;
var oldOwner = Interlocked.CompareExchange(ref owner, null, null);
if (oldOwner != null && !oldOwner.IsSelectable(RedisCommand.PSUBSCRIBE))
if (owners.Count != 0 && !owners.All(o => o.IsSelectable(RedisCommand.PSUBSCRIBE)))
{
if (UnsubscribeFromServer(channel, CommandFlags.FireAndForget, null, true) != null)
{
changed = true;
}
oldOwner = null;
owners.Clear();
}
if (oldOwner == null && SubscribeToServer(multiplexer, channel, CommandFlags.FireAndForget, null, true) != null)
if (owners.Count == 0 && SubscribeToServer(multiplexer, channel, CommandFlags.FireAndForget, null, true) != null)
{
changed = true;
}
Expand Down