SolCache is a scalable, in-memory message cache for Direct messaging. It allows client applications connecting to Solace PubSub+ to request the most current messages for a topic of interest when they come online, or when they start subscribing to topics that they were not originally subscribed to. For example, a real-time stock quote display may need to retrieve the latest value for a symbol when a user expresses interest in monitoring that symbol. In such a situation, it is useful to have a standalone application that saves the last messages sent for a topic of interest, and responds to client requests for copies of the messages published to that topic.
To provide real-time delivery of messages, SolCache utilizes the message broker message bus to cache live data messages according to topic subscriptions and deliver cached messages for corresponding topics that are specified in client requests. The message bus load balances client requests for messages amongst a group of message caches (SolCache Instances) hosted on Linux computer platforms. This group of SolCache Instances (a Cache Cluster) is configured to listen for a common set of topics published to a specific Message VPN. When published messages match the topic subscriptions for the Cache Cluster, the SolCache Instances cache those live data messages. Client cache requests for messages matching those topics can then be serviced by any of the Cache Instances within the Cache Cluster. Clients can request a particular number of cached messages or messages that are no older than a specific time.