Using a Heartbeat to Detect Disconnection
The AMPS client includes a heartbeat feature to help applications detect disconnection from the server within a predictable amount of time. Without using a heartbeat, an application must rely on the environment to notify it when a disconnect occurs. For applications that are simply receiving messages, it can be impossible to tell whether a socket is disconnected or whether there are simply no incoming messages for the client.
When you set a heartbeat, the AMPS client sends a heartbeat message to the AMPS server at a regular interval, and waits a specified amount of time for the response. If the operating system reports an error on send, or if the server does not respond within the specified amount of time, the AMPS client considers the server to be disconnected.
The AMPS client processes heartbeat messages asynchronously. If your application publishes messages in a loop (a synchronous operation), or the message handler is receiving significant amount of messages at the moment, the client may fail to respond to heartbeat messages in a timely manner and may be disconnected by the server.
The Client class, included with the AMPS JavaScript client, contains a disconnect handler and other features for building highly-available applications. The Client includes features for managing a list of failover servers, resuming subscriptions, republishing in-flight messages, and other functionality that is commonly needed for high availability. This section covers the use of a custom disconnect handler in the event that the behavior of the Client does not suit the needs of your application. 60East recommends using the provided disconnect handler unless there is specific behavior that does not meet your needs (for example, if your application does not want to reconnect to AMPS in the event of a disconnection).
The Client class in the JavaScript library combines functionality of both Client and HAClient classes of other AMPS client libraries.
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