Distributed caching is an important aspect of cloud-based applications, be it for on-premises, public or hybrid cloud environments. It facilitates incremental scaling, allowing the cache to grow and incorporate the data growth. In this blog we will explore distributed caching on the cloud and why it is useful for environments with high data volume and load.

Traditional Caching Challenges

Traditional caching servers are usually deployed with limited storage and CPU speed. Often these caching infrastructures reside on data centers that are on-premises. I am referring to a non-distributed caching server. Traditional distributed caching comes with numerous challenges:

• Hard-to-scale cache storage and CPU speed on non-cloud node servers.
• High operational cost to manage infrastructure and unutilized hardware resources.
• Inability to scale and manage traditional distributed caching (since it is non-containerized).
• Possibility of servers crashing if client load is higher than actual.
• Chances of stale data during programmatic sync-up with multiple data center servers.
• Slow data synchronization between servers and various data centers.

What is Distributed Caching

Caching is a technique to store the state of data outside of the main storage and store it in high-speed memory to improve performance. In a microservices environment, all apps are deployed with their multiple instances across various servers/containers on the hybrid cloud. A single caching source is needed in a multicluster Kubernetes environment on the cloud to persist data centrally and replicate it on its own caching cluster. It will serve as a single point of storage to cache data in a distributed environment.

Benefits of Distributed Caching on Cloud

• Periodic caching of frequently used read REST APIs’ response ensures faster API read performance.
• Reduced database network calls by accessing cached data directly from distributed caching databases.
• Resilience and fault tolerance by maintaining multiple copies of data at various caching databases in a cluster.
• High availability by auto-scaling the cache databases, based on load or client requests.
• Storage of session secret tokens like JSON Web Token (ID/JWT) for authentication and authorization purposes for microservices apps containers.
• Faster read and write access in-memory if it's used as a dedicated database solution for high-load mission-critical applications.
• Avoid unnecessary roundtrip data calls to persistent databases.
• Auto-scalable cloud infrastructure deployment.
• Containerization of distributed caching libraries/solutions.
• Consistent read data from any synchronized connected caching data centers.
• Minimal to no outage, high availability of caching data.
• Faster data synchronization between caching data servers.

Recommended Distributed Caching Database Tools

The following are popular industry-recognized caching servers:

• Redis
• Memcached
• GemFire and
• Hazelcast databases

Redis: It’s one of the most popular distributed caching services. It supports different data structures. It’s an open-source, in-memory data store used by millions of developers as a database, cache, streaming engine and message broker. It also has an enterprise version. It can be deployed in containers on private, public and hybrid clouds etc. It provides consistent and faster data synchronization between different data centers.

Memcached: It is an open-source, high-performance, distributed memory object caching system. It is generic in nature but intended for use in speeding up dynamic web applications by alleviating database load. Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from the results of database calls, API calls or page rendering. Memcached is simple yet powerful. Its simple design promotes easy, quick deployment and development. It solves many data-caching problems, and the API is available in various commonly used languages.

GemFire: It provides distributed in-memory data-grid cache, powered by Apache Geode open source. It scales data services on demand to support high performance. It’s a key-value store that performs read and write operations at fast speeds. It offers highly available parallel message queues, continuous availability and an event-driven architecture to scale dynamically with no downtime.

It provides multisite replication. As data size requirements increase to support high-performance, real-time apps, they can scale linearly with ease. Applications get low-latency responses to data-access requests and always return fresh data. It maintains transaction integrity across distributed nodes and supports high-concurrency, low-latency data operations of the application. It also provides node failover and cross-data center or multi-data center replication to ensure applications are resilient, whether on-premises or in the cloud.

Hazelcast: Hazelcast is a distributed computation and storage platform for consistent low-latency querying, aggregation and stateful computation against event streams and traditional data sources. It allows you to quickly build resource-efficient, real-time applications. You can deploy it at any scale from small edge devices to a large cluster of cloud instances. A cluster of Hazelcast nodes share both the data storage and computational load, which can dynamically scale up and down. When you add new nodes to the cluster, the data is automatically rebalanced across the cluster. The computational tasks (jobs) that are currently in a running state, snapshot their state and scale with processing guarantee.

Ways to Deploy Distributed Caching on Hybrid Cloud

These are recommended ways to deploy and setup distributed caching, be it on public cloud or hybrid cloud:

• Open source distributed caching on traditional VM instances.
• Open source distributed caching on Kubernetes container. I would recommend deploying on Kubernetes container for high availability, resiliency, scalability and faster performance.
• Enterprise commercial off-the-shelf distributed caching deployment on VM and container. I would recommend the enterprise version because it will provide additional features and support.
• Public cloud offers managed services of distributed caching for open source and enterprise tools like Redis, Hazelcast and Memcached, etc.
• Caching servers can be deployed on multiple sources like on-premises and public cloud together, public servers or only one public server in different availability zones.

Conclusion

Distributed caching is now a de-facto requirement for distributed microservices applications in a distributed deployment environment on a hybrid cloud. It addresses concerns in important use cases like maintaining user sessions when cookies are disabled on the web browser, improving API query read performance, avoiding operational costs and database hits for the same type of requests, managing secret tokens for authentication and authorization, etc.

Distributed cache syncs data on hybrid clouds automatically without any manual operation and always gives the latest data. I would recommend industry-standard distributed caching solutions like Redis, Hazelcast and Memcached. We need to choose better distributed caching technology in the cloud, based on use cases.