Wednesday October 03, 2007 Using memcached in Solaris Zones
These days everyone seems to use memcached, a high-performance, distributed memory object caching system, intended for use in speeding up web applications. Performance can be greatly improved from moving away from disk fetch to a RAM fetch. Here is an excellent article explaining memcached taking LiveJournal as a case study.Do you know that memcached daemons can be set up on Solaris Zones too? For this you need to download memcached package from the Cool Stack site.
What you need to get?
1. Cool Stack
2. memcached Java Client APIs (Get this jar and this jar).
Create and Boot Zones
I have created 3 zones zonea, zoneb and zonec to test memcached. For information on creating Solaris zones read this article.
I'm using SXDE 9/07
OK you don't have SXDE? Go go go get it!
Here is the status of my zones:
# zoneadm list -vc
ID NAME STATUS PATH BRAND IP
0 global running / native shared
4 zonea running /zones/zonea native shared
5 zoneb running /zones/zoneb native shared
6 zonec running /zones/zonec native shared
Start memcached on all Zones
Follow the Cool Stack site for installing Cool Stack on your zones. When you do a pkgadd -d <memcached*.pkg>, memcached gets installed in all the available zones even though they are not in a running state.
When everything is set, these commands should work fine:
zonea# ./opt/coolstack/bin/memcached -u phantom -d -m 100 -l 129.158.224.242 -p 11111
zoneb# ./opt/coolstack/bin/memcached -u phantom -d -m 100 -l 129.158.224.231 -p 11112
zonec# ./opt/coolstack/bin/memcached -u phantom -d -m 100 -l 129.158.224.243 -p 11113
I'm starting memcached as non-root user on all all zones with 100 MB memory bucket. This should be OK for testing but ideally in a production setup it should be around a terabyte.
If you don't know already, each Solaris zone can bind to an IP and port through the virtual interface. So I don't need 3 NICs or 3 machines but just 3 zones.
Test memcached
I assume that you have set the classpath pointing to the downloaded jars. Phantom sake, use Netbeans for simplicity. I'm going to store an object in-memory and retrieve it from the memcached daemon running on zonea.
....
//Interact with zonea
MemcachedClient c;
try {
c = new MemcachedClient(new InetSocketAddress
("129.158.224.242", 11111));
String test=new String("I'm going to be cached!");
c.set("mykey", 180, test);
Object obj=c.get("mykey");
System.out.println((String)obj);
c.delete("mykey");
} catch (IOException ex) {
ex.printStackTrace();
}
...
I'm storing an object for 3 mins. After retrieveing the object, I clean the cache. When you compile and run here is the output:
2007-10-03 10:38:49.615 INFO net.spy.memcached.MemcachedConnection: Connected to {QA sa=/129.158.224.242:11111, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} immediately
I'm going to be cached!
From your code, you can also connect to multiple memcached servers and store objects.
This is quite ineresting. I'm going to halt one zone and will try to store object in-memory on all the three zones.
# zoneadm -z zonea halt
# zoneadm list -vc
ID NAME STATUS PATH BRAND IP
0 global running / native shared
5 zoneb running /zones/zoneb native shared
6 zonec running /zones/zonec native shared
- zonea installed /zones/zonea native shared
Now zonea is no longer running memcached because zonea zone itself is down.
Here is the modified code:
MemcachedClient c;
try {
//zonea, zoneb and zonec
c=new MemcachedClient(AddrUtil.getAddresses
("129.158.224.242:11111
129.158.224.231:11112
129.158.224.243:11113"));
String test=new String("I'm going to be cached on all zones!");
c.set("mykey2", 180, test);
Object obj=c.get("mykey2");
System.out.println((String)obj);
c.delete("mykey2");
} catch (IOException ex) {
ex.printStackTrace();
}
I'm trying to store the object on all the available servers. But zonea is offline.
Here is the output:
2007-10-03 11:18:27.678 INFO net.spy.memcached.MemcachedConnection:
Added {QA sa=/129.158.224.242:11111, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
2007-10-03 11:18:27.682 INFO net.spy.memcached.MemcachedConnection:
Connected to {QA sa=/129.158.224.231:11112, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} immediately
2007-10-03 11:18:27.684 INFO net.spy.memcached.MemcachedConnection:
Connected to {QA sa=/129.158.224.243:11113, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} immediately
I'm going to be cached on all zones!
The object is queued for insertion whenever zonea comes up. It would be interesting to test the automatic failover behaviour of memcached considering the fact that memcached is a mother of all hashtables and there should be sufficient fail safe plumbing required between running instances of memcached daemons. In my future posts, I will try to show you how to use DTrace for memcached debugging.
( Oct 03 2007, 12:26:03 AM PDT ) Permalink