zwave-js / zwave-js-ui / 32818987033

16%

push

github

fix(api): coalesce throttled calls when `fn` outlasts its wait window (#4779)

## Problem

`ZwaveClient.throttle` stamped `lastUpdate: Date.now()` before calling
`fn()`. A function slower than its own `wait` window therefore never
coalesced. The next call always saw `entry.lastUpdate + wait < now`, and
ran the leading edge again.

This hit `_updateBroadcastNodeValues` at `wait = 1000`. Its
`_doUpdateBroadcastNodeValues` calls
`broadcastInstance.getDefinedValueIDs()`. That walk visits
`getDefinedValueIDs()` and `getValueMetadata()` on every physical node
in the network. The rebuild then emits `valueChanged` for each resulting
value.

On a ~340-node network that walk takes seconds. Startup therefore ran a
full rebuild for every node that became ready. One trailing rebuild
would have covered them all.

Evidence: the driver log in zwave-js#9024 shows a uniform ~2.4–2.9 s gap
between consecutive per-node `Retrieving priority route to node X...`
lines. The gap holds for the entire 6-minute startup. No serial traffic
happens in between.

### Before — every call runs the leading edge

```mermaid
sequenceDiagram
    autonumber
    participant N as node ready event
    participant T as throttle, wait=1000
    participant F as _doUpdateBroadcastNodeValues

    Note over T: lastUpdate is stamped before fn runs

    N->>T: call at t=0
    T->>T: lastUpdate = 0
    T->>F: fn
    Note over F: walks all 340 nodes,<br/>blocks the event loop until t=2500
    F-->>T: returns at t=2500

    N->>T: call at t=2500
    Note over T: 0 + 1000 already elapsed<br/>leading edge again
    T->>T: lastUpdate = 2500
    T->>F: fn
    F-->>T: returns at t=5000

    N->>T: call at t=5000
    Note over T: 2500 + 1000 already elapsed<br/>leading edge again
    T->>F: fn
    Note over N,F: one full rebuild per node ready,<br/>nothing ever coalesces
```

### After — the window starts when `fn` returns

```mermaid
sequenceDiagram
    autonumber
    participant N as node ready event
    par... (continued)

535 of 4550 branches covered (11.76%)

Branch coverage included in aggregate %.

24 of 25 new or added lines in 1 file covered. (96.0%)

988 of 7025 relevant lines covered (14.06%)

2.17 hits per line