Apama 10.3 | Apama Documentation | Connecting Apama Applications to External Components | Working with Connectivity Plug-ins | Using Connectivity Plug-ins | Host plug-ins and configuration
Host plug-ins and configuration
The first element in the configuration of a chain must be a host plug-in. This is a special type of plug-in that controls how the correlator interacts with the chain. The type of plug-in will determine in which form events are passed to and accepted from the chain. The host plug-in must use a compatible type with the first codec (or, if no codecs specified, the transport), otherwise errors will be reported and events will not be delivered.
Overview of host plug-ins
The following host plug-ins are supported:
The eventMap plug-in translates EPL events to and from nested maps, which allows chains to convert arbitrary structured data into forms that can be automatically translated into EPL events without having to know the exact definition of the EPL event, provided the field names of the event definition match the keys in the map. See Translating EPL events using the apama.eventMap host plug-in for further information.
The eventString plug-in transfers events in Apama string event format, as used by the engine_send and engine_receive tools and the Apama client library.
Common configuration properties
All Apama host plug-ins take the following configuration properties:
Configuration Property
Optional. Defines the channel or channels to which the chain subscribes in order to receive events from the correlator.
subscribeChannels is only recommended for chains defined as startChains. Dynamic chains will have their channel subscription specified either from EPL or by the chain manager which will override any setting in the configuration file.
To send an event to a chain from EPL, use the EPL send statement with the name of a channel to which the chain has subscribed.
Type of configuration: string or list of strings.
Default: the chain name.
Optional. Defines the default channel to deliver events from the transport to the correlator from the chain.
Some chain managers provide a value for defaultChannel. It is not permitted to specify defaultChannel for chains used by such chain managers. It is recommended only for chains defined as startChains or which you intend to create from EPL.
Chains can also specify a channel name in the metadata of each message. A channel provided in metadata takes precedence over this configuration value.
Type of configuration: string.
Default: the default channel is an empty string (""), thus delivering the event to all public contexts.
Optional. If set to true, any events which will be received by this chain will not also be sent to contexts subscribed to the same channel. It is assumed that this receiver may send the events back into the correlator to be received by subscribed contexts. This is typically used when this chain is connected to a message bus. Any other external receivers are unaffected.
Type of configuration: boolean.
Default: false.
Optional. A textual description which will appear in the Management interface (see also Using the Management interface).
Optional. A textual address for the remote component (if any) to which this chain connects. This address will also appear in the Management interface.

Copyright © 2013-2018 | Software AG, Darmstadt, Germany and/or Software AG USA, Inc., Reston, VA, USA, and/or its subsidiaries and/or its affiliates and/or their licensors.