Definitions

Requirements

In order to use this functionality you need to enable Blueriq External Flow Component.

Configuration

To configure the External Flow Container to work on the runtime you have to do the following:

1. Enable external-flow profile in bootstrap.properties.
2. When using mutliple runtimes enable the correct redis sessions
   
3. When using a single runtime choose either to use redis or the in memory variant.

Using other datastore implementation then Redis

Blueriq provides IExternalFlowStore interface which can be used to interact with a generic datastore. A default implementation is already provided in the Blueriq External Flow Component. If other datastore implementation is desired you can follow these instructions.

Modeling an External Flow

Decoupling Pattern 8: External Flow Container

Flow type: external

Container type: AQ_ExternalFlow

Module type: Contract module

External Flow Endpoints

See External Flow Endpoints.

External Sessions Lifecycle

External sessions are created when different runtimes start an external flow on the current runtime. The external sessions are closed when the http session has expired or it was idle. When the user logs out from the host project or the host session simply expired, the external session has no knowledge of that and will remain open even if not used.

To mitigate the problem an mechanism was introduced that uses the same redis connection (check configuration section) to store information about the host session, and the target runtime will check for all of its host sessions if any of them are closed or are still opened. Every time it finds one that was closed, then it will also close the external sessions that were created by that host session.

Authentication & Authorisation 

When an external flow is executed on a different runtime than the one that the current project is open, there needs to be a way in order for the roles of the currently logged in user to be validated on the target runtime where the external flow resides to. In order to support this, the authentication details of the main project are saved in the External flow Data Store and when the external flow is executed, the authentication is retrieved on the runtime where the external flow resides on, and is set up as if the same user has logged in on that runtime.

Security

Content-Security-Policy (needed when hostname and/or port are different)

Set Content-Security-Policy on the source to allow access to the remote server:

# Content Security Policy
blueriq.security.click-jacking-protection.content-security-policy.default-src='self' http://target:port

Cross-Origin Resource Sharing (needed when using multiple domains)

When running an external flow from an AQ_ExternalFlow container, requests could be made between different domains. Therefore, for the external flows to work, you need to configure the Cross-Origin Resource Sharing mechanism. For more information, see Security: Cross-Origin Resource Sharing

Known limitations

The following list contains all currently known limitiations for external flows. In general the external flow should not be used to start new sessions within the session of the external flow. 

• The host and the target runtimes must have the same Blueriq version (major and minor, patch and java)
• AQ_StartProject cannot be used and is not supported. It will certainly not work with different tabs when executed on different servers.
• The development tools functionality is limited, reloading projects at different url's does not work
• External flows only work correctly when using V2 of the frontend api (UI REST API V2)
• DCM2.0 in combination with external flows is not supported
• Using external flows leads to more sessions on the backend and thus more memory usage. This should be taken into account when assigning resources to the server