[jboss-user] [JBossCache] - Re: Cache loader questions
servus, ai dreptate, scuze :( you are right, my bad. The thing is that the cache loader itself know how to load data in batch, but the calling code does not use this. I've updated http://jira.jboss.com/jira/browse/JBCACHE-1221 View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4108843#4108843 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4108843 ___ jboss-user mailing list jboss-user@lists.jboss.org https://lists.jboss.org/mailman/listinfo/jboss-user
[jboss-user] [JBossCache] - Re: Cache loader questions
Hi, I think you're wrong about point 1. I wrote a simple test:
package aditsu;
|
| import java.io.IOException;
| import java.util.HashMap;
| import java.util.Map;
|
| import org.apache.log4j.BasicConfigurator;
| import org.jboss.cache.Cache;
| import org.jboss.cache.DefaultCacheFactory;
| import org.jboss.cache.Fqn;
|
| public class JDBCTest {
|
| public static void main(final String... args) throws IOException {
| BasicConfigurator.configure();
| Cache c =
DefaultCacheFactory.getInstance().createCache("aditsu/cache-jdbc.xml");
| Map m = new HashMap();
| c.put(new Fqn("a"), m);
| c.put(new Fqn("b"), m);
| c.put(new Fqn("c"), m);
| c.stop();
| c.destroy();
| System.in.read();
| c.create();
| c.start();
| }
| }
and this is my cache config:
|
|
|
| org.jboss.cache.transaction.DummyTransactionManagerLookup
| REPEATABLE_READ
| LOCAL
|
|
| false
| /
|
| org.jboss.cache.loader.JDBCCacheLoader
|
| cache.jdbc.table.name=jbosscache
| cache.jdbc.table.create=true
| cache.jdbc.table.drop=false
| cache.jdbc.table.primarykey=jbosscache_pk
| cache.jdbc.fqn.column=fqn
| cache.jdbc.fqn.type=varchar(255)
| cache.jdbc.node.column=node
| cache.jdbc.node.type=bytea
| cache.jdbc.parent.column=parent
| cache.jdbc.driver=org.postgresql.Driver
| cache.jdbc.url=jdbc:postgresql://localhost/jbc
| cache.jdbc.user=postgres
| cache.jdbc.password=
| cache.jdbc.sql-concat=concat(1,2)
|
| false
| true
| false
| false
|
|
|
|
|
When I start the cache the 2nd time (after pressing enter), I get these log
entries:
5226 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select node from jbosscache where fqn=? (/)
5229 [main] DEBUG org.jboss.cache.CacheImpl.JBossCache-Cluster - cache mode is
local, will not create the channel
5229 [main] DEBUG org.jboss.cache.loader.CacheLoaderManager - preloading
transient state from cache loader [EMAIL PROTECTED]
5229 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select fqn from jbosscache where parent=? (/)
5232 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select node from jbosscache where fqn=? (/a)
5235 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select fqn from jbosscache where parent=? (/a)
5238 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select node from jbosscache where fqn=? (/c)
5241 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select fqn from jbosscache where parent=? (/c)
5245 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select node from jbosscache where fqn=? (/b)
5266 [main] DEBUG org.jboss.cache.loader.JDBCCacheLoader - executing sql:
select fqn from jbosscache where parent=? (/b)
So it's executing not one but TWO queries for every single node! That's
definitely not what I want, and contradicts what you said.
Adrian
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[jboss-user] [JBossCache] - Re: Cache loader questions
Salut, mersi pt. raspuns :) (Hi, thanks for your answer) 1. This is good news, I'll look at the JDBCCacheLoader code For the writes, I already have a custom implementation. 2. This was not answered properly, but from what you say it looks like at least 2.2 is not currently possible. 3. I'm using sync replication anyway, at least for now, but the question was about the cache loader (which has to be async for performance reasons). I can implement this feature manually (to have each instance attempt to flush the changes from the whole cluster to db, asynchronously), but I was hoping JBC already had this option. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4106230#4106230 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4106230 ___ jboss-user mailing list jboss-user@lists.jboss.org https://lists.jboss.org/mailman/listinfo/jboss-user
[jboss-user] [JBossCache] - Re: Cache loader questions
anonymous wrote : 1. Is it possible to do reads and writes in batches? Obviously, if I have 1 million records and I want to preload them all, it's better to do one "SELECT *" rather than one "SELECT ID" followed by 1 million "SELECT * WHERE ID=?". JDBCCacheLoader works like that (starting with 2.0). anonymous wrote : | Similarly, if I have 1 million updates to perform, it's better to group them in batches (asynchronously), and reduce the number of db transactions. Nice one, I've created http://jira.jboss.com/jira/browse/JBCACHE-1221 for this. anonymous wrote : | 2. When I add a new cache to the replicated cluster (with a shared cache loader), can it preload all the necessary data from the cache loader (not blocking the cluster in any way during this operation), and then get the latest changes from the cluster (*all* and *only* the changes) so that it is up to date? | You can disable state transfer then and preload data on startup. If other caches write async then this won't work, though. We have some ideas of handling state transfer more efficiently, but not a clear date on when those will be implemented anonymous wrote : | 3. I understand that with a shared cache loader, the cache that originates a change is also the one that writes it to the cache loader. yes anonymous wrote : What happens if the cache loader writes asynchronously, and that cache instance goes down after completing the transaction but before flushing the data to the db? Is it possible to have another cache write it instead? Not. After all that's the drawback of having async writings, you're not gonna be notified whether they failed or not. If it's critical for you to know the data is persisted I think you should use sync replication. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4106062#4106062 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4106062 ___ jboss-user mailing list jboss-user@lists.jboss.org https://lists.jboss.org/mailman/listinfo/jboss-user
