Tanzu GemFire Basics

VMware GemFire is the data store within VMware Tanzu GemFire for VMs. A GemFire for VMs service instance requires a small amount of administrative setup, and any app will use a limited portion of the API.

The GemFire for VMs architectural model is a client-server model. The clients are apps or microservices, and the servers are a set of cluster servers maintained by a GemFire for VMs service instance. The servers provide a low-latency, consistent, fault-tolerant data store within GemFire for VMs.

Client Server Model

The cluster holds data in key/value pairs. Each pair is called an entry. Entries are logically grouped into sets called regions. A region is a map (or dictionary) data structure.

The app (client) uses GemFire for VMs as a cache. A cache lookup (read) is a get operation on a region. The cache operation of a cache write is a put operation on a region. The command-line interface, called gfsh, facilitates region administration. Use gfsh to create and destroy regions within the GemFire for VMs service instance.

The App's Location

A running app's location affects how it communicates with the GemFire for VMs service instance. Apps may run in one of three locations:

  • In the services foundation where the GemFire for VMs service instance runs. These apps require no extra communication support.
  • In an app foundation, where a user-provided service instance proxies the communication to the GemFire for VMs service instance. Communication with the GemFire for VMs service instance requires a service gateway.
  • Outside of any platform, where a platform is composed of any and all foundations. Communication with the GemFire for VMs service instance requires a service gateway.

Interaction of Apps and Foundations

To use a service gateway, the operator must Configuring a Service Gateway. The developer must Provide Optional Parameters when creating the GemFire for VMs service instance. And, the app must be given and use properties that authenticate and authorize Communicating with a Service Instance through the service gateway.

Member Communication

When a client connects to the cluster, it first connects to a locator. The locator replies with the IP address of a server for it to talk to. The client then connects to that server.

Client Connects to Locator

When the client wants to read or write data, it sends a request directly to the server.

Client Sends Server Request

If the server doesn't have the data locally, it fetches it from another server.

Server Fetches from Another Server

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