Plugin Development

Plugins are identified by method signature only. While there are ICommandPlugin and IEndpointPlugin interfaces, their usage is not mandatory.

All plugin operations are also cooperative in nature. For example, once engine sends control to any of the plugin methods (e.g., ReceiveAsync), it will wait until control is returned before proceeding.

There are two kinds of plugins: Command and Endpoint.

• Command plugin executes an action that is not dependant on the external systems
• Endpoint plugin allows for handling of messages to/from external system

Command Plugin

The following methods must be defined for all command plugins:

• static Task<AASeqNodes> ExecuteAsync(ILogger logger, AASeqNodes parameters, CancellationToken cancellationToken)

ExecuteAsync Method

This static method will attempt to execute an command.

It accepts the following arguments:

• logger: used to log any troubleshooting information
• parameters: any parameters needed; this is a cloned version that can be freely modified
• cancellationToken: token for handling timeouts; its usage is not mandatory if operation has short duration

Returns executed nodes.

Method should raise exception in the case of invalid parameters.

Endpoint Plugin

The following methods must be defined for all endpoint plugins:

• static Object CreateInstance(ILogger logger, AASeqNodes configuration)
• Task StartAsync(CancellationToken cancellationToken)
• Task<AASeqNodes> SendAsync(Guid id, string messageName, AASeqNodes parameters, CancellationToken cancellationToken)
• Task<Tuple<string, AASeqNodes>> ReceiveAsync(Guid id, string messageName, CancellationToken cancellationToken)

CreateInstance Method

This static method will return the instance of the endpoint.

It accepts the following arguments:

• logger: used to log any troubleshooting information
• configuration: any configuration needed; this is a cloned version that can be freely modified

Returns plugin object.

Method should raise exception in the case of invalid configuration only. No attempt to start endpoint should be done at this time.

StartAsync Method

Starts endpoint processing.

It accepts the following arguments:

• cancellationToken: token for handling timeouts; its usage is not mandatory if operation has short duration

Returns nothing.

Method should raise exception in the case endpoint cannot be started.

Exception should be thrown only if configuration is erroneous. Opening of connection should not be done here but in a separate start method.

StartAsync Method

Starts any necessary connection.

SendAsync Method

Attempts to send a message.

It accepts the following arguments:

• id: provided is used to match with message received in Receive (if needed)
• messageName: contains name of the message to send
• parameters: any parameters needed; this is a cloned version that can be freely modified
• cancellationToken: token for handling timeouts; its usage is not mandatory if operation has short duration

Returns sent nodes.

Method can raise exceptions.

ReceiveAsync Method

Attempts to receive a message.

It accepts the following arguments:

• id: provided is used to match with message sent in Send (if needed)
• parameters: any parameters needed; this is a cloned version that can be freely modified
• cancellationToken: token for handling timeouts; its usage is not mandatory if operation has short duration

Return is a tuple containing received message name (messageName) and any data (data).

Method can raise exceptions.

Variable Plugin

The following methods must be defined for all variable plugins:

• static string? GetVariableValue(ILogger logger, string argument)

GetVariableValue Method

This static method will attempt to return a variable value.

It accepts the following arguments:

• logger: used to log any troubleshooting information
• argument: argument to the variable

Returns variable value or null if variable value cannot be determined.

Method should not raise exceptions.