Event stream

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The event stream is the system’s own bus. Actor lifecycle events go through it, every dead letter is published on it, and so is whatever your actors publish themselves. This panel is a live tail of it.

Column	Meaning
seq	Per-session counter; a gap means events were dropped
time	When the event was published
event	Constructor name of the event, or its `typeof`
payload	A one-line preview; click the row for the whole thing

The filter box matches on both the event type and the payload text, so OrderPlaced and order-4711 both narrow the tail.

Clear empties the tail and resets the dropped counter.

To stop the tail so you can read it, use Pause in the header — it stops every panel at once, this one included. Events published while time is stopped are held, and arrive in order when you resume, so pausing costs you nothing but the delay. This panel used to carry a Pause button of its own that discarded what arrived — the right call for a button that stopped one tail, and the wrong one for a button that stops the world.

Nothing is recorded until you look

The server installs its observer when this panel subscribes and removes it when the last one goes away. That is different from the tracing panel, which records from the moment DevTools attaches, and the difference is deliberate: tracing is already opt-in, while the event bus is always live, so an always-on observer would run on every actor start and stop for a panel nobody opened.

The consequence is that the panel opens empty and fills as events arrive. An idle system shows nothing, and that is not a fault.

When the tail falls behind

The server buffers events between flushes and drops the oldest past its cap, then tells the panel how many it dropped. The panel says so above the table rather than quietly showing a shorter list — a reader draws conclusions from what is not there, so a tail that silently skips is worse than one that admits it.

Raise the buffer if you are losing events you need:

const devtoolsOptions = DevToolsOptions.create()
  .withEventBufferCapacity(2_000)
  .withEventFlushIntervalMs(100);

Cluster topics

Below the tail is the list of distributed PubSub topics this node knows about. It is a cluster extension, so a single-node system reports that it was never started — which is a different answer from “started, with no topics”, and the panel makes that distinction rather than showing an empty list for both.

Topic names only: the mediator’s CurrentTopics reply carries no subscriber counts, and changing a cluster wire type for one column in one panel is not a trade worth making.