Exception interception with Redis Cluster - StackExchange.Redis
Configured Redis Cluster Server on Ubuntu 14.0 LTS Server (AZURE VM) using the official redis tutorial with no loopback IP as @Marcgravell pointed out, but getting MOVED exception for some keys when using Stackexchange.Redis client. Hi @Marcgravell, Can you shed some light on this. Thank.
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Finally, I got my program. Thanks to @ hrishi18pathak. I downloaded the code from https://github.com/hrishi18pathak/StackExchange.Redis/tree/SEClusteringBugFix with changes from July 17, 2015. Major changes in the ConnectionMultiplexer and ConfigurartionOptions class.
ConnectionMultiplexer.cs (modified UpdateClusterRange () method, added IsNodeCompatibleWithConfiguration () method):
internal void UpdateClusterRange(ClusterConfiguration configuration)
{
if (configuration == null) return;
foreach (var node in configuration.Nodes)
{
// do not update cluster range if the node configuration is incompatible with the multiplexer
// endpoints configuration. If a user has specified endpoints in the multiplexer configuration using
// Dns endpoints, Stackexchange.redis returns the ConnectionMultiplexer object successfully
// after connecting to all the nodes in the connection string (using their host names).
// Also, before returning the multiplexer object it updates the mapping of nodes to their clusterslots
// and this mapping is of the format "DNS hostname:port" : "clusterSlotNumber".
// However at the same time, the client also issues "CLUSTER NODES" command to each of the nodes in the above list
// (to determine master and slave configuration) and re-updates the cluster mapping with the output of the clusternodes command
// which now is going to contain IP addresses (redis-server itself does not understand host names).
// So the cluster mapping is now updated to the format: "IP Address" : "clusterSlotNumber"
// If the StackExchange.Redis has not been able to connect to all the nodes using their IP addresses by the time the first command (GET,SET)
// is issued to the cluster, it results in failure to connect to that particular node resulting in the "MOVED ERROR"
// (since it tries to hit a random node in the list subsequently)
if (node.IsSlave || node.Slots.Count == 0 || !IsNodeCompatibleWithConfiguration(node)) continue;
foreach (var slot in node.Slots)
{
var server = GetServerEndPoint(node.EndPoint);
if (server != null) serverSelectionStrategy.UpdateClusterRange(slot.From, slot.To, server);
}
}
}
/// <summary>
/// Checks if the specified node has the same format as that of
/// the endpoints specified in the multiplexer configuration i.e.
/// if all nodes are dns endpoints then the specified node has to be a dns endpoint
/// to be compatible.
/// </summary>
/// <param name="node"></param>
/// <returns>True if node is compatible with multiplexer configuration</returns>
private bool IsNodeCompatibleWithConfiguration(ClusterNode node)
{
return (this.configuration.HasAllDnsEndPoints() && (node.EndPoint is DnsEndPoint)) ||
(!this.configuration.HasDnsEndPoints() && !(node.EndPoint is DnsEndPoint));
}
ConfigurationOptions.cs (Added HasAllDnsEndPoints () method)
internal bool HasAllDnsEndPoints()
{
return !endpoints.Any(ep => !(ep is DnsEndPoint));
}
However, I need to check for any implications with this fix.
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