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Exercise 5 - Event Based Gateways and Intermediate Events

DSF-TeamAbout 7 min

Prerequisites | Exercise 1 | Exercise 1.1 | Exercise 2 | Exercise 3 | Exercise 4 | Exercise 5

Exercise 5 - Event Based Gateways and Intermediate Events

In the final exercise we will look at message flow between three organizations as well as how to continue a waiting process if no return message arrives. With this exercise we will add a third process and complete a message loop from Test_DIC to Test_COR to Test_HRP back to Test_DIC.

Introduction

Managing Multiple- and Missing Messages

If an existing and started process instance is waiting for a message from another organization, the corresponding FHIR Task may never arrive. Either because the other organization decides to never send the "message" or because some technical problem prohibits the Task resource from being posted to the DSF FHIR server. This would result in stale process instances that never finish.

In order to solve this problem we can add an Event Based Gateway to the process waiting for a response and then either handle a Task resource with the response and finish the process in a success state or fire of an Intermediate Timer Catch Event after a defined wait period and finish the process in an error state. The following BPMN collaboration diagram shows how the process at the first organization would look like if two different message or no message could be received:

Timer Events

For Timer Events the duration until the timer fires is specified using the ISO 8601 Durations format. Examples can be found in the Camunda 7 documentation.

Matching Process Instances With Business Keys

In the example above the first organization is sending a "message" to the second and waiting for a reply. In order to correlate the return message with the waiting process instance, a unique identifier needs to be exchanged between both process instances. Within the DSF this is implemented using the process instance business-key and a corresponding Task.input parameter. For 1:1 communication relationships this is handled by the DSF BPE servers automatically, but the corresponding Task profiles need to define the business-key input parameter as mandatory.

If multiple message are send in a 1:n relationship with a n:1 return an additional correlation-key needs to be configured in order to correlate every bidirectional communication between two DSF instances.

ActivityDefinitions for the DSF

FHIR ActivityDefinition resources are used to announce what processes can be instantiated at a given DSF instance and contain the authorization rules for the specified process. ActivityDefinition for the DSF need to comply with the http://highmed.org/fhir/StructureDefinition/activity-definition profile, with authorization rules configured using the http://highmed.org/fhir/StructureDefinition/extension-process-authorization extension.

The authorization extension needs to be configured at least once and has four sub extensions:

message-name [1..1]

String value specifying the message name of Message Start Event, Intermediate Message Catch Event or Message Receive Task this authorization rule should match. Can only be specified once per authorization rule extension.

task-profile [1..1]

Canonical URL value specifying the Task profile this authorization rule should match. Can only be specified once per authorization rule extension.

requester [1..]

Coding value matching entries from the http://highmed.org/fhir/ValueSet/process-authorization-requester ValueSet:

recipient [1..]

Coding value matching entries from the http://highmed.org/fhir/ValueSet/process-authorization-recipient ValueSet.

The local organization of a DSF instance is configured using the environment variables ORG_HIGHMED_DSF_FHIR_SERVER_ORGANIZATION_IDENTIFIER_VALUE for the DSF FHIR server and ORG_HIGHMED_DSF_BPE_FHIR_SERVER_ORGANIZATION_IDENTIFIER_VALUE for the DSF BPE server.

Authorization Extension Example

The following example specifies that process execution can only be requested by a organization with a specific identifier and only allows execution of the process in the DSF instance of an organization with a specific identifier.

<extension url="http://highmed.org/fhir/StructureDefinition/extension-process-authorization">
	<extension url="message-name">
		<valueString value="some-message-name" />
	</extension>
	<extension url="task-profile">
		<valueCanonical value="http://foo.org/fhir/StructureDefinition/profile|#{version}" />
	</extension>
	<extension url="requester">
		<valueCoding>
			<extension url="http://highmed.org/fhir/StructureDefinition/extension-process-authorization-consortium-role">
				<extension url="consortium">
					<valueIdentifier>
						<system value="http://highmed.org/sid/organization-identifier" />
						<value value="identifier.consortium.org" />
					</valueIdentifier>
				</extension>
				<extension url="role">
					<valueCoding>
						<system value="http://highmed.org/fhir/CodeSystem/organization-role" />
						<code value="SOME_ROLE" />
					</valueCoding>
				</extension>
			</extension>
			<system value="http://highmed.org/fhir/CodeSystem/process-authorization" />
			<code value="REMOTE_ROLE" />
		</valueCoding>
	</extension>
	<extension url="recipient">
		<valueCoding>
			<extension url="http://highmed.org/fhir/StructureDefinition/extension-process-authorization-consortium-role">
				<extension url="consortium">
					<valueIdentifier>
						<system value="http://highmed.org/sid/organization-identifier" />
						<value value="identifier.consortium.org" />
					</valueIdentifier>
				</extension>
				<extension url="role">
					<valueCoding>
						<system value="http://highmed.org/fhir/CodeSystem/organization-role" />
						<code value="SOME_ROLE" />
					</valueCoding>
				</extension>
			</extension>
			<system value="http://highmed.org/fhir/CodeSystem/process-authorization" />
			<code value="LOCAL_ROLE" />
		</valueCoding>
	</extension>
</extension>

Exercise Tasks

  1. Modify the HelloCosMessage and use the value from the Task.input parameter of the helloDic Task to send it to the highmedorg_helloCos process via a Task.input parameter in the helloCos Task. Override the getAdditionalInputParameters to configure a Task.input parameter to be send.
  2. Modify the highmedorg_helloCos process to use a Message End Event to trigger the process in file hello-hrp.bpmn. Figure out the values for the instantiatesUri, profile and messageName input parameters of the Message End Event based on the AcitvityDefinition in file hello-hrp.xml.
  3. Modify the highmedorg_helloDic process:
  4. Modify the process in file hello-hrp.bpmn and set the process definition key and version. Figure out the appropriate values based on the AcitvityDefinition in file hello-hrp.xml.
  5. Add the process in file hello-hrp.bpmn to the TutorialProcessPluginDefinition and configure the FHIR resources needed for the three processes.
  6. Add the HelloCos, HelloHrpMessage , HelloHrp and GoodbyeDicMessage classes as spring beans.

Solution Verification

Maven Build and Automated Tests

Execute a maven build of the dsf-process-tutorial parent module via:

mvn clean install -Pexercise-5

Verify that the build was successful and no test failures occurred.

Process Execution and Manual Tests

To verify the highmedorg_helloDic, highmedorg_helloCos and highmedorg_helloHrp processes can be executed successfully, we need to deploy them into DSF instances and execute the highmedorg_helloDic process. The maven install build is configured to create a process jar file with all necessary resources and copy the jar to the appropriate locations of the docker test setup.

  1. Start the DSF FHIR server for the Test_DIC organization in a console at location .../dsf-process-tutorial/test-setup:
docker-compose up dic-fhir

Verify the DSF FHIR server started successfully.

  1. Start the DSF BPE server for the Test_DIC organization in a second console at location .../dsf-process-tutorial/test-setup:
docker-compose up dic-bpe

Verify the DSF BPE server started successfully and deployed the highmedorg_helloDic process.

  1. Start the DSF FHIR server for the Test_COS organization in a third console at location .../dsf-process-tutorial/test-setup:
docker-compose up cos-fhir

Verify the DSF FHIR server started successfully.

  1. Start the DSF BPE server for the Test_COS organization in a fourth console at location .../dsf-process-tutorial/test-setup:
docker-compose up cos-bpe

Verify the DSF BPE server started successfully and deployed the highmedorg_helloDic process.

  1. Start the DSF FHIR server for the Test_HRP organization in a fifth at location .../dsf-process-tutorial/test-setup:
docker-compose up hrp-fhir

Verify the DSF FHIR server started successfully. You can access the webservice of the DSF FHIR server at https://hrp/fhir.
The DSF FHIR server uses a server certificate that was generated during the first maven build. To authenticate yourself to the server you can use the client certificate located at .../dsf-process-tutorial/test-data-generator/cert/Webbrowser_Test_User/Webbrowser_Test_User_certificate.p12 (Password: password).

  1. Start the DSF BPE server for the Test_HRP organization in a sixth console at location .../dsf-process-tutorial/test-setup:
docker-compose up hrp-bpe

Verify the DSF BPE server started successfully and deployed the highmedorg_helloHrp process. The DSF BPE server should print a message that the process was deployed. The DSF FHIR server should now have a new ActivityDefinition resource. Go to https://hrp/fhir/ActivityDefinition to check if the expected resource was created by the BPE while deploying the process. The returned FHIR Bundle should contain a three ActivityDefinition resources. Also, go to https://hrp/fhir/StructureDefinition?url=http://highmed.org/fhir/StructureDefinition/task-hello-hrp to check if the expected Task profile was created.

  1. Start the highmedorg_helloDic process by posting a specific FHIR Task resource to the DSF FHIR server of the Test_DIC organization: Execute therefore the main method of the org.highmed.dsf.process.tutorial.TutorialExampleStarter class to create the Task resource needed to start the highmedorg_helloDic process.

Verify that the FHIR Task resource was created at the DSF FHIR server and the highmedorg_helloDic process was executed by the DSF BPE server of the Test_DIC organization. The DSF BPE server of the Test_DIC organization should print a message showing that a Task resource to start the highmedorg_helloCos process was sent to the Test_COS organization.
Verify that a FHIR Task resource was created at the DSF FHIR server of the Test_COS organization and the highmedorg_helloCos process was executed by the DSF BPE server of the Test_COS organization. The DSF BPE server of the Test_COS organization should print a message showing that a Task resource to start the highmedorg_helloHrp process was send to the Test_HRP organization.

Based on the value of the Task.input parameter you send, the highmedorg_helloHrp process will either send a goodbyDic message to the Test_DIC organization or finish without sending a message.

To trigger the goodbyDic message, use send-response as the http://highmed.org/fhir/CodeSystem/tutorial#tutorial-input input parameter.

Verify that the highmedorg_helloDic process either finishes with the arrival of the goodbyDic message or after waiting for two minutes.

Prerequisites | Exercise 1 | Exercise 1.1 | Exercise 2 | Exercise 3 | Exercise 4 | Exercise 5