I am currently using Spring Boot Starter 1.4.2.RELEASE, and Geode Core 1.0.0-incubating via Maven, against a local Docker configuration consisting of a Geode Locator, and 2 cache nodes.
I've consulted the documentation here:
http://geode.apache.org/docs/guide/developing/distributed_regions/locking_in_global_regions.html
I have configured a cache.xml file for use with my application like so:
<?xml version="1.0" encoding="UTF-8"?>
<client-cache
xmlns="http://geode.apache.org/schema/cache"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://geode.apache.org/schema/cache
http://geode.apache.org/schema/cache/cache-1.0.xsd"
version="1.0">
<pool name="serverPool">
<locator host="localhost" port="10334"/>
</pool>
<region name="testRegion" refid="CACHING_PROXY">
<region-attributes pool-name="serverPool"
scope="global"/>
</region>
</client-cache>
In my Application.java I have exposed the region as a bean via:
@SpringBootApplication
public class Application {
@Bean
ClientCache cache() {
return new ClientCacheFactory()
.create();
}
@Bean
Region<String, Integer> testRegion(final ClientCache cache) {
return cache.<String, Integer>getRegion("testRegion");
}
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
And in my "service" DistributedCounter.java:
@Service
public class DistributedCounter {
@Autowired
private Region<String, Integer> testRegion;
/**
* Using fine grain lock on modifier.
* @param counterKey {@link String} containing the key whose value should be incremented.
*/
public void incrementCounter(String counterKey) {
if(testRegion.getDistributedLock(counterKey).tryLock()) {
try {
Integer old = testRegion.get(counterKey);
if(old == null) {
old = 0;
}
testRegion.put(counterKey, old + 1);
} finally {
testRegion.getDistributedLock(counterKey).unlock();
}
}
}
I have used gfsh to configure a region named /testRegion - however there is no option to indicate that it's type should be "GLOBAL", only a variety of other options are available - ideally this should be a persistent, and replicated cache though so the following command:
create region --name=/testRegion --type=REPLICATE_PERSISTENT
Using the how-to at: http://geode.apache.org/docs/guide/getting_started/15_minute_quickstart_gfsh.html it is easy to see the functionality of persistence and replication on my two node configuration.
However, the locking in DistributedCounter, above, does not cause any errors - but it just does not work when two processes attempt to acquire a lock on the same "key" - the second process is not blocked from acquiring the lock. There is an earlier code sample from the Gemfire forums which uses the DistributedLockService - which the current documentation warns against using for locking region entries.
Is the use-case of fine-grained locking to support a "map" of atomically incremental longs a supported use case, and if so, how to appropriately configure it?
