memcached itself knows nothing about other nodes in a system. How the keys
are distributed is entirely dependent upon your client implementation. I'm
not familiar with BeIT client, but from reading through the wiki page, I
would expect it to be splitting the keys among your memcache servers
approximately equally. I say approximately, because hashing functions are
probabilisitic. With only 27 keys, I wouldn't be surprised to see
significant deviation here. At large numbers of keys, I would expect pretty
even distribution though.
I think more important than how you are fetching keys from each server is
how you're using the BeIT client -- which you don't show here. Do you set
it up to do replication or sharding? If replication, what you're seeing is
expected. If sharding, I'd say it's unexpected.
You can figure out what it is doing by using a packet sniffer (eg, ngrep,
wireshark) and seeing when the client sets keys to which boxes.
~Ryan
On Thu, May 15, 2014 at 1:39 PM, Jonathan Minond <jmin...@gmail.com> wrote:
> I am seeing something that struck me as a little odd.
>
> From my reading, as I understand, in a memcached environment, each
> memcache node contains a portion of the objects in the cluster.
>
> So, I would expect something like if I have 27 keys and 3 nodes.
>
> Each node is holding ~9 keys/objects.... is that correct to assume?
>
> So, to test out...
> <add key="MemCached.Endpoint"
> value="server1:11211,server2:11211,server3:11211" />
>
> As a client, I am using the BeIT Memcached Client for .NET (
> code.google.com/p/beitmemcached/)
>
> To get the keys, I am using Telnet, to get slabs, and then the items, as
> described by Boris here:
> groups.google.com/forum/#!topic/memcached/YyzonP9HUi0
>
> 1) I loop through my collection of hosts
> 2) Do the telnet process against that host
> 3) Collect all the info.
>
> It seems to me, that I am getting the same keys listed on all 3
> servers..... ?
> *I did not expect this, and I am hoping someone can explain.*
>
> To clarify:
> This is how I do a GET:
>
>
> And this is how I am trying to get the list of keys.... there is a bit of
> debug code buried in there, but it should still be clear:
> (TelNetConn = A simple telnet helper)
>
> List<string> ret = new List<string>();
>
> string memCacheEndPointAddress =
> Config.GetValueWithDefault("MemCached.Endpoint", "localhost:11211");
>
> string[] points = memCacheEndPointAddress.Split(new[] { ',' },
> StringSplitOptions.RemoveEmptyEntries);
>
> foreach (string h in points)
> {
> string[] hParts = h.Split(new[] { ':' },
> StringSplitOptions.RemoveEmptyEntries);
>
> string cacheHost = hParts[0];
> TelNetConn tc = new TelNetConn(cacheHost,
> Convert.ToInt32(hParts[1]));
>
> if (tc.IsConnected)
> {
> ret.Add("HOST: " + cacheHost);
>
> tc.WriteLine("stats items");
> String s = tc.Read();
> String[] sLines = s.Split(
> new string[] { Environment.NewLine },
> StringSplitOptions.RemoveEmptyEntries);
>
> foreach (string sl in sLines)
> {
> if (sl == "END") continue;
>
> String[] slParts = sl.Split(new[] { ':' },
> StringSplitOptions.RemoveEmptyEntries);
>
> int slabID = Convert.ToInt32(slParts[1]);
> string slabType = slParts[2];
>
> if (slabType.StartsWith("number") ||
> slabType.StartsWith("age"))
> {
> tc.WriteLine("stats cachedump " +
> slabID + " 100");
>
> s = tc.Read();
>
> if (!String.IsNullOrEmpty(s))
> {
> if (s != "END")
> {
> // ret.Add("FULL: " + s);
>
> if (s.StartsWith("ITEM "))
> {
> string[] itemparts =
> s.Split(new[] { ' ' }, StringSplitOptions.None);
> string key = itemparts[1];
> ret.Add("ITEM: " + key);
> }
> }
> }
> }
> }
>
> }
> else
> {
> ret.Add("HOST: " + cacheHost + " NOT
> CONNECTED");
> }
>
> tc.Dispose();
> }
>
> --
>
> ---
> You received this message because you are subscribed to the Google Groups
> "memcached" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to memcached+unsubscr...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>
--
---
You received this message because you are subscribed to the Google Groups
"memcached" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to memcached+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
