Question
· Oct 11

How can I implement an event-sourced architecture with journal-based replay using IRIS globals?

#InterSystems IRIS

I want to build an event store using raw globals and replay events for rebuilding state. Can I hook into IRIS journaling or write my own event log and replay engine?

Discussion (1)2
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DC AI Bot · Oct 11

Implementing event-sourced architecture with journal-based replay using IRIS globals includes the following approaches:

  1. Using IRIS Journaling:

    • IRIS journaling records all updates made to a database. This ensures recovery and replay capabilities in cases of failure. Journaling can be set up to track all database modifications and replay them using utilities like ^JRNRESTO. It provides mechanisms to recover databases to a point captured in the journal files [1].
    • You can configure journaling functions, customize journal properties, and manage them using utilities like ^JOURNAL. Journaling archives are ideal for ensuring reliable storage and replay scenarios [2].

  2. Custom Event Store in Globals:

    • You can design your event store using IRIS globals, ensuring efficient storage and retrieval. Mapping event data to specific nodes in globals helps maintain the event sequence and guarantees quick access to individual events [3].
    • InterSystems IRIS supports multi-dimensional global structures, which are suitable for modeling events efficiently [4].

  3. Replay Mechanism:

    • Replay can happen by iterating over the global structure or journal files to reconstruct the application state based on the event history. Utilities like ^JRNRESTO facilitate restoring from journal files [2].
    • For configurations focused purely on custom global-based solutions, you must develop a replay engine capable of processing event data stored in the respective global.

  4. Event Handlers:

    • If dynamic event handling is required, server-side constructs such as system events could be utilized. Packages and tools like ToolBox-4-Iris provide enhancements, adding capabilities for synchronous or asynchronous event handling using queues [3].

To leverage IRIS journaling effectively:
- Activate journaling on databases where events are stored.
- Use IRIS utilities for maintaining the organization of journal files such as purging and switching journals periodically.
- Alternatively, set up a custom logging and replay mechanism by persisting raw event data into globals and developing a parsing engine for replay functionality [2][1].

If deeper customization or use-case-specific configurations are required, integration with tools like event queues or creating bespoke event handlers might be needed [1][2].

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