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Dynamic Discovery Protocol

Overview

The dynamic discovery protocol combines reconnect logic with a discovery agent to dynamically create a list of brokers to which the client can connect. The discovery protocol invokes a discovery agent in order to build up a list of broker URIs. The protocol then randomly chooses a URI from the list and attempts to establish a connection to it. If it does not succeed, or if the connection subsequently fails, a new connection is established to one of the other URIs in the list.

URI syntax

Example 19 shows the syntax for a discovery URI.

Example 19. Dynamic Discovery URI

discovery://(DiscoveryAgentUri)?Options

DiscoveryAgentUri is URI for the discovery agent used to build up the list of available brokers. Discovery agents are described in Discovery Agents.

The options, ?Options, are specified in the form of a query list. The discovery options are described in Table 15. You can also inject transport options as described in Setting options on the discovered transports.

[Tip]Tip

If no options are required, you can drop the parentheses from the URI. The resulting URI would take the form discovery://DiscoveryAgentUri

Transport options

The discovery protocol supports the options described in Table 15.

Table 15. Dynamic Discovery Protocol Options

OptionDefaultDescription
initialReconnectDelay 10Specifies, in milliseconds, how long to wait before the first reconnect attempt.
maxReconnectDelay 30000Specifies, in milliseconds, the maximum amount of time to wait between reconnect attempts.
useExponentialBackOff trueSpecifies if an exponential back-off is used between reconnect attempts.
backOffMultiplier 2Specifies the exponent used in the exponential back-off algorithm.
maxReconnectAttempts 0Specifies the maximum number of reconnect attempts before an error is sent back to the client. 0 specifies unlimited attempts.

Sample URI

Example 20 shows a discovery URI that uses a multicast discovery agent.

Example 20. Discovery Protocol URI

discovery://(multicast://default)?initialReconnectDelay=100

Setting options on the discovered transports

The list of transport options, Options, in the discovery URI can also be used to set options on the discovered transports. If you set an option not listed in Setting options on the discovered transports, the URI parser attempts to inject the option setting into every one of the discovered endpoints.

Example 21 shows a discovery URI that sets the TCP connectionTimeout option to 10 seconds.

Example 21. Injecting Transport Options into a Discovered Transport

discovery://(multicast://default)?connectionTimeout=10000

The 10 second timeout setting is injected into every discovered TCP endpoint.

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