Tuesday, May 24, 2016

Hazelcast : In-Memory NoSQL Solution

If you are evaluating high-performance NoSQL solutions such as: Redis, Riak, Couchbase, MongoDB, Cassandra etc. or in even rarer cases if you’re evaluating caching solutions such as Memcached or EHcache, it’s possible that your best choice may be Hazelcast: Hazelcast uses a considerably different approach to any of the above projects, and yet for some classes of people looking for a Key-Value store, Hazelcast may be the best option for you.




So lets look at Hazelcast and why it is better alternative for above mentioned systems, Hazelcast is an In-Memory Data Grid, not a NoSQL database.
advantages and disadvantages of using Hazelcast in-memory solution, first of all as being key-value store into the memory, it has some default advantages are speed and read efficiency but also some natural disadvantages as storing map into memory are scalability and volatility, as we know that size of RAM is always less than the total available disk space, as RAM is more expensive than the disk, so being in-memory store space is always been a constant and second one as being flash storage, RAM refreshes itself on process restart, resulting into the data loss. Hazelcast addressing this shortcomings of the in-memory stores by providing efficient and convenient solution.
In Hazelcast, scalability issue is addressed by clustering solution, as joining hundreds nodes into the cluster, we may aggregate more than terabytes of in-memory space, to accommodate Hazelcast map into the memory. Of course this not going to be compared with disk space as its been 100 times more than memory but depending upon use case some terabytes of space is sufficient for the in-memory operations or else this solution may use with some backend data store.

Volatility, in Hazelcast volatility handled by peer to peer data distribution, so every block of data has multiple copies(replication across the cluster) of it present on different locations, as any node/rack goes down because of some issue, we can recover data from other copies present on other locations. The number of backup copies can be configured as depending upon the data criticality. Too much copies of the data into the cluster may reduce the overall availability of working memory to other operations. Hazelcast addresses the tuning problem of the cluster by providing ways to make your cluster available and reliable, including setting up backup process for example servers on one rack would be set to back up on another rack, so failure of entire rack can be managed gracefully.
Hazelcast also address the Rebalancing problem of the cluster, whenever node is added/removed to/from the cluster can be lead to moving data across the cluster to rebalancing it. If the node crashes because of some issues, the data copy(primary) on dead node has to be re-owned by the another node who is having replica of that data copy(secondary) becoming primary and backed up on another node to make cluster fail-safe again. this process may consume more cluster resources like CPU, RAM, network etc. might lead to latency into the process during this whole process.
Also in addition to the above benefits, Hazelcast also make sure that Java Garbage Collection process should not be having any effect on the terabytes of data stored onto memory specifically on heap as your heap gets bigger, garbage collection might cause delay in your application response time. So memory store is Hazelcast with native storage support to avoid garbage collector to causing delay in application; resulting in more efficiency and throughput.

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