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Infinispan cache putforexternalread
Автор: Gura | Category: Xmr cryptocurrency calculator | Октябрь 2, 2012This lends itself great to distributed processing as the iteration is handled entirely by the implementation in this case Infinispan. I therefore am glad to introduce for Infinispan 8, the feature Distributed Streams! This allows for any operation you can perform on a regular Stream to also be performed on a Distributed cache assuming the operation and data is marshallable.
Marshallability When using a distributed or replicated cache, the keys and values of the cache must be marshallable. This is the same case for intermediate and terminal operations when using the distributed streams. Normally you would have to provide an instance of some new class that is either Serializable or has an Externalizer registered for it as described in the marshallable section of the user guide.
However, Java 8 also introduced lambdas, which can be defined as serializable very easily although it is a bit awkward. An example of this serialization can be found here. Some of you may also be aware of the Collectors class which is used with the collect method on a stream. Unfortunately, all of the Collectors produced are not able to be marshalled. As such, Infinispan has added a utility class that can work in conjunction with the Collectors class.
This allows you to still use any combination of the Collectors classes and still work properly when everything is required to be marshalled. Parallelism Java 8 streams naturally have a sense of parallelism. That is that the stream can be marked as being parallel. This in turn allows for the operations to be performed in parallel using multiple threads. The best part is how simple it is to do. The stream can be made parallel when first retrieving it by invoking parallelStream or you can optionally enable it after the Stream is retrieved by just invoking parallel.
The new Distributed streams from Infinispan take this one step further, which I am calling parallel distribution. That is that since data is already partitioned across nodes we can also allow operations to be ran simultaneously on different nodes at the same time.
This option is enabled by default. However this can be controlled by using the new CacheStream interface discussed just below. Also, to be clear, the Java 8 parallel can be used in conjunction with parallel distribution. This just means you will have concurrent operations running on multiple nodes across multiple threads on each node. CacheStream interface There is a new interface Cachestream provided that allows for controlling additional options when using a Distributed Stream.
If a cache is configured for invalidation, every time data is changed in a cache, other caches in the cluster receive a message informing them that their data is now stale and should be removed from memory and from any local store. Figure 5. Invalidation cache Sometimes the application reads a value from the external store and wants to write it to the local cache, without removing it from the other nodes. To do this, it must call Cache. Invalidation mode can be used with a shared cache store.
A write operation will both update the shared store, and it would remove the stale values from the other nodes' memory. The benefit of this is twofold: network traffic is minimized as invalidation messages are very small compared to replicating the entire value, and also other caches in the cluster look up modified data in a lazy manner, only when needed.
Never use invalidation mode with a local, non-shared, cache store. The invalidation message will not remove entries in the local store, and some nodes will keep seeing the stale value. An invalidation cache can also be configured with a special cache loader, ClusterLoader. When ClusterLoader is enabled, read operations that do not find the key on the local node will request it from all the other nodes first, and store it in memory locally.
In certain situation it will store stale values, so only use it if you have a high tolerance for stale values. Synchronous or asynchronous replication When synchronous, a write blocks until all nodes in the cluster have evicted the stale value.
When asynchronous, the originator broadcasts invalidation messages but does not wait for responses. That means other nodes still see the stale value for a while after the write completed on the originator. Transactions Transactions can be used to batch the invalidation messages. Transactions acquire the key lock on the primary owner. With pessimistic locking, each write triggers a lock message, which is broadcast to all the nodes. During transaction commit, the originator broadcasts a one-phase prepare message optionally fire-and-forget which invalidates all affected keys and releases the locks.
With optimistic locking, the originator broadcasts a prepare message, a commit message, and an unlock message optional. Either the one-phase prepare or the unlock message is fire-and-forget, and the last message always releases the locks. Scattered caches Scattered caches are very similar to distributed caches as they allow linear scaling of the cluster. Unlike distributed caches, the location of data is not fixed; while we use the same Consistent Hash algorithm to locate the primary owner, the backup copy is stored on the node that wrote the data last time.
When the write originates on the primary owner, backup copy is stored on any other node the exact location of this copy is not important. This has the advantage of single Remote Procedure Call RPC for any write distributed caches require one or two RPCs , but reads have to always target the primary owner. That results in faster writes but possibly slower reads, and therefore this mode is more suitable for write-intensive applications. Storing multiple backup copies also results in slightly higher memory consumption.
In order to remove out-of-date backup copies, invalidation messages are broadcast in the cluster, which generates some overhead. This lowers the performance of scattered caches in clusters with a large number of nodes. When a node crashes, the primary copy may be lost. Therefore, the cluster has to reconcile the backups and find out the last written backup copy.
This process results in more network traffic during state transfer. You cannot use scattered caches with transactions or asynchronous replication. The protocol automatically selects primary owner for the writes and therefore the write in distributed mode with two owner requires single RPC inside the cluster, too.
Therefore, scattered cache would not bring the performance benefit. With asynchronous communications, the originator node does not receive any acknowledgement from the other nodes about the status of the operation, so there is no way to check if it succeeded on other nodes. We do not recommend asynchronous communications in general, as they can cause inconsistencies in the data, and the results are hard to reason about.
Nevertheless, sometimes speed is more important than consistency, and the option is available for those cases. There is one caveat: The asynchronous operations do NOT preserve the program order. If a thread calls cache. Return values with asynchronous replication Because the Cache interface extends java. Map, write methods like put key, value and remove key return the previous value by default. In some cases, the return value may not be correct: When using AdvancedCache.
When using asynchronous communications. When there are multiple concurrent writes to the same key, and the cache topology changes. Transactional caches return the correct previous value in cases 3 and 4. However, transactional caches also have a gotcha: in distributed mode, the read-committed isolation level is implemented as repeatable-read.
In caches with optimistic locking, writes can also return stale previous values. Write skew checks can avoid stale previous values. Configuring initial cluster size Infinispan handles cluster topology changes dynamically.
This means that nodes do not need to wait for other nodes to join the cluster before Infinispan initializes the caches. If your applications require a specific number of nodes in the cluster before caches start, you can configure the initial cluster size as part of the transport. Procedure Open your Infinispan configuration for editing. Set the minimum number of nodes required before caches start with the initial-cluster-size attribute or initialClusterSize method.
Set the timeout, in milliseconds, after which the Cache Manager does not start with the initial-cluster-timeout attribute or initialClusterTimeout method. Save and close your Infinispan configuration. Infinispan cache configuration Cache configuration controls how Infinispan stores your data.

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[VDM19] Boosting your applications with distributed caches/datagrids by Katia Aresti
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