Hi,
You can try with using EntryProcessor. Please take a look at the following
example:
public class EntryUpdater implements EntryProcessor<String, String, String> {
@Override
public String process(MutableEntry<String, String> entry,
Object... arguments) throws EntryProcessorException {
if (!entry.exists()) {
// Cache does not contain a mapping for the given key.
String newValue = getNewValue();
entry.setValue(newValue);
}
else {
// The entry is already exists, just return the existing value.
}
return entry.getValue();
}
}
private static String processKey(String key) {
return cache.invoke(key, new EntryUpdater());
}
[1]
https://ignite.apache.org/releases/latest/javadoc/org/apache/ignite/IgniteCache.html#invoke-K-org.apache.ignite.cache.CacheEntryProcessor-java.lang.Object...-
Thanks,
S.
чт, 13 сент. 2018 г. в 15:06, HEWA WIDANA GAMAGE, SUBASH <
[email protected]>:
> Thank you for the prompt response.
>
>
>
> I agree there’s a race condition here. But the problem of the suggestion
> is, “getNewValue()” will get called even for cache hits. This getNewValue
> eventually calling some backend legacy API and the caching layer is setup
> to reduce the load for it.
>
>
>
> *From:* Вячеслав Коптилин [mailto:[email protected]]
> *Sent:* Thursday, September 13, 2018 4:08 AM
> *To:* [email protected]
> *Subject:* Re: Ignite Cluster: Cache Misses happening for existing keys
>
>
> This email is from an external source - exercise caution regarding links
> and attachments. Please visit cybersecurity.fmr.com/phishing/ to learn
> more.
>
>
>
> Hello,
>
>
>
> Your code contains the following obvious race:
>
> String value = *cache*.get(key);
> *if *(value == *null*) {
> *cache*.put(key, *getNewValue*());
> *LOG*.info(*"Cache put key={} "*, key);
> }
>
> It's easy to imagine that two threads managed to execute get() method and got
> null value before put() operation is called.
>
> Please try to modify the code as follows:
>
> if (cache.putIfAbsent(key, getNewValue())) {
>
> LOG.info("Cache put key={} ", key);
>
> }
>
> else {
>
> LOG.info("Cache hit key={}", key);
>
> }
>
>
>
> [1]
> https://ignite.apache.org/releases/latest/javadoc/org/apache/ignite/IgniteCache.html#putIfAbsent-K-V-
>
>
>
> Thanks,
>
> S.
>
>
>
> чт, 13 сент. 2018 г. в 6:29, HEWA WIDANA GAMAGE, SUBASH <
> [email protected]>:
>
> Hi all,
>
> We’re observing this in a 3 node server cluster(3 separate JVMs, in 3
> separate VMs within same datacenter, node to node latency is 2-3
> milliseconds within the network).
>
>
>
> As with following code is wrapped inside an http API, and that API is
> getting called by a 5000 users ramping up(60seconds) forever, hitting 3
> nodes in a round robin manner.
>
>
>
> *With this, for same cache key, I could see more than one “Cache put key=”
> log appearing with in 15mins window(actually I am getting this duplicate
> put logs after 2-3mins of the load test).. *
>
>
>
> For the SAME cache key, there cannot be more than one put within 15mins.
> Based on cache size, it’s well below eviction size, and since it’s well
> within the expiry window, looks to me some timing issue when replicating
> the cache between the nodes.
>
>
>
> Time between same key cache put logs is about 8-12 seconds usually. Am I
> doing something wrong here ? Any way we can make a cache.put operation
> synchronously complete only upon a full node replication (not quite sure
> whether it helps though)?
>
>
>
> Version: Ignite 1.9
>
>
>
> *Code to create the cache*
>
>
>
> IgniteConfiguration cfg = *new *IgniteConfiguration();
> cfg.setDiscoverySpi(*getDiscoverySpi*());
> *// static ip list on tcp discovery *cfg.setClientMode(*false*);
> cfg.setIncludeEventTypes(EventType.*EVT_NODE_SEGMENTED*,EventType.
> *EVT_NODE_FAILED*);
> Ignite ignite = Ignition.*start*(cfg);
>
> ignite.events().localListen(event -> {
> *LOG*.info(*"Cache event received: {} "*, event);
> *return true*;},EventType.*EVT_NODE_SEGMENTED*,
> EventType.*EVT_NODE_FAILED*);
>
>
>
> CacheConfiguration<String,String> cc = *new *CacheConfiguration<>();
> cc.setName(*"mycache1"*);
> cc.setExpiryPolicyFactory(CreatedExpiryPolicy.*factoryOf*(*new
> *Duration(TimeUnit.*MINUTES*, 15)));
> cc.setCacheMode(CacheMode.*REPLICATED*);
> LruEvictionPolicy evictionPolicy = *new *LruEvictionPolicy();
> evictionPolicy.setMaxMemorySize(500 * 1024 * 1024);
> cc.setEvictionPolicy(evictionPolicy);
>
>
> IgniteCache<String,String> cache = ignite.getOrCreateCache(cc);
>
>
>
>
>
> *Code to cache operations.(following method can be accessed by multiple
> threads at the same time)*
>
>
>
> *private static *String processKey(String key) {
> String value = *cache*.get(key);
> *if *(value == *null*) {
> *cache*.put(key, *getNewValue*());
> *LOG*.info(*"Cache put key={} "*, key);
> } *else *{
> *LOG*.info(*"Cache hit key={}"*, key);
> }
> *return *value;
> }
>
>
>
>
>
>
>
>
