Eventum 2.5.0: Template Dispatch API

Eventum 2.5.0 is out. The headline is the template dispatch API — three new actions that let a template skip an event, ask the generator to pick templates again, or end generation altogether. This release also adds a random IPv4 helper for CIDR subnets.

Template dispatch API

Until now, a template either produced an event or raised an error. There was no graceful way to skip a timestamp when the underlying data was missing, or to stop a finite dataset cleanly. The new dispatch object adds three actions any template can call at render time:

• dispatch.drop() — discard the current event. Dropped events now appear in the pipeline metrics and the monitoring panel, so drops are distinguishable from successful renders.
• dispatch.next() — discard the current output and ask the generator to pick templates again for the same timestamp. Behavior depends on the picking mode (all, any, chance, spin, chain, fsm).
• dispatch.exhaust() — signal that generation is finished. The generator shuts down gracefully and no more timestamps are processed.

Quick example: skip when the session pool is empty

{%- set sessions = shared.get('sessions', []) -%}
{%- if sessions | length == 0 -%}
  {%- do dispatch.drop() -%}
{%- endif -%}
{%- set sess = sessions.pop(0) -%}
{%- do shared.set('sessions', sessions) -%}
{"session": "{{ sess.id }}", "timestamp": "{{ timestamp.isoformat() }}"}

One caveat worth knowing up front: dispatch actions do not roll back state. Anything already written to locals, shared, or globals stays in effect, so check preconditions before mutating state. See the dispatch API docs for the full reference and per-mode behavior.

Random IPv4 in a CIDR subnet

The module.rand.network namespace gains ip_v4_in_subnet — pass a CIDR string and get a random host address from inside it.

{%- set client_ip = module.rand.network.ip_v4_in_subnet("10.0.1.0/24") -%}

Handy when events should look like they originate from a specific subnet — an office network, a Kubernetes pod CIDR, a VPN range — instead of being scattered across the entire IPv4 space.

Read the full changelog for every detail.