What is "configuredOnly" used for in ConnectionMultiplexer.GetEndPoints()?

Question

I am using the fantastic StackExchange.Redis library to implement ObjectCache. One of the interface methods to implement in ObjectCache is long GetCount(...) which returns the number of keys in the database. It looks like this can be satisfied by the IServer.DatabaseSize(...) method in StackExchange.Redis.

I plan on fetching the server endpoints from ConnectionMultiplexer.GetEndPoints(), getting an IServer for each endpoint, and then querying the database size for each database I am interested in on each server (ignore size discrepancies for the moment).

Now, ConnectionMultiplexer.GetEndPoints() has an optional parameter called "configuredOnly". What is the consequence of not providing it, versus true, versus false?

In the ConnectionMultiplexer.GetEndPoints() implementation, I see that it returns the EndPoints from the multiplexer configuration if configuredOnly is true, or else returns EndPoints from an array called "serverSnapshot".

As best as I can tell, "serverSnapshot" is populated here, which seems to be populated as servers are connected, or at least are attempted to be connected to.

Does GetEndPoints(true) return all EndPoints that were configured on the ConnectionMultiplexer? Does GetEndPoints() and GetEndPoints(false) return EndPoints that actually are connected/valid? The documentation for the GetEndPoints method with respect to the configuredOnly parameter is sparse, and my subsequent use of the returned EndPoints needs one behavior and not the other.

Answer 1

When configuredOnly is set to true, GetEndPoints() only returns endpoints for the Redis servers explicitly specified in the call to ConnectionMultiplexer.Connect(). Alternately when configuredOnly is false, endpoints are returned for every Redis servers in the cluster, whether or not they were specified in the initial ConnectionMultiplexer.Connect() call.

Somewhat strangly, if you use DNS names in the ConnectionMultiplexer.Connect() call, GetEndPoints(false) will return rows for both the DNS name and also the resolved IP address. For example, with a six-node Redis cluster the following code:

ConnectionMultiplexer redis = ConnectionMultiplexer("localhost:6379,localhost:6380");
foreach (var endpoint in redis.GetEndPoints(false))
{
  Console.WriteLine(endpoint.ToString());
}

will output

$127.0.0.1:6379
Unspecified/localhost:6379
Unspecified/localhost:6380
127.0.0.1:6380
127.0.0.1:6381
127.0.0.1:6382
127.0.0.1:6383
127.0.0.1:6384

If I had called redis.GetEndPoints(true), only Unspecified/localhost:6379 and Unspecified/localhost:6380 would be returned.