Make all hardcoded timing/buffer constants configurable with good defaults #129

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opened 2026-03-01 10:35:41 +00:00 by ash · 0 comments

ash commented

2026-03-01 10:35:41 +00:00

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Problem

Several components have hardcoded timing and buffer constants that should be configurable:

ChangeNotifier (`changenotifier.go`)

changeNotifierBufferSize = 64 — subscriber channel buffer
Missing: SSE polling fallback interval (currently no fallback at all — dropped notifications = permanently stale UI)

PGChangeRelay (`pgstore/change_relay.go`)

changeReconnectDelay = 1s — reconnection delay after connection loss
Broadcast timeout 2s — PG NOTIFY timeout

ChannelEventBus (`eventbus_channel.go`)

channelBufSize = 256 — subscriber channel buffer

Solution

ChangeNotifier

Add options pattern:

type ChangeNotifierOption func(*ChangeNotifier)

func WithBufferSize(size int) ChangeNotifierOption
func WithFallbackPoll(interval time.Duration) ChangeNotifierOption // NEW: periodic re-notify as safety net

The fallback poll is critical: if a notification is dropped (buffer full), the SSE handler currently has NO way to recover. Add an optional ticker that fires a synthetic change so SSE handlers re-read from DB. Default: 5s. Set to 0 to disable.

Alternatively, add a SubscribeWithPoll(projection, interval) that returns a channel that also receives periodic ticks — letting each subscriber choose their own fallback interval.

PGChangeRelay

Add to constructor or options:

type PGChangeRelayOption func(*PGChangeRelay)

func WithReconnectDelay(d time.Duration) PGChangeRelayOption
func WithBroadcastTimeout(d time.Duration) PGChangeRelayOption

Defaults: reconnect 1s, broadcast 2s.

ChannelEventBus

Add option:

func WithChannelBufferSize(size int) ChannelEventBusOption

Default: 256.

Requirements

All current constants become defaults
Options pattern for configuration (consistent with rest of eskit)
Godoc on every option explaining what it does and the default value
Tests for custom values
Benchmarks for any hot-path changes
The SSE fallback poll is the most important addition here — it turns "permanently stale" into "at most N seconds stale"

Related: subscription.Config already does this correctly — PollInterval, RetryBaseDelay, etc. are all configurable with defaults. Match that pattern.

## Problem Several components have hardcoded timing and buffer constants that should be configurable: ### ChangeNotifier (`changenotifier.go`) - `changeNotifierBufferSize = 64` — subscriber channel buffer - **Missing:** SSE polling fallback interval (currently no fallback at all — dropped notifications = permanently stale UI) ### PGChangeRelay (`pgstore/change_relay.go`) - `changeReconnectDelay = 1s` — reconnection delay after connection loss - Broadcast timeout `2s` — PG NOTIFY timeout ### ChannelEventBus (`eventbus_channel.go`) - `channelBufSize = 256` — subscriber channel buffer ## Solution ### ChangeNotifier Add options pattern: ```go type ChangeNotifierOption func(*ChangeNotifier) func WithBufferSize(size int) ChangeNotifierOption func WithFallbackPoll(interval time.Duration) ChangeNotifierOption // NEW: periodic re-notify as safety net ``` The fallback poll is critical: if a notification is dropped (buffer full), the SSE handler currently has NO way to recover. Add an optional ticker that fires a synthetic change so SSE handlers re-read from DB. Default: 5s. Set to 0 to disable. Alternatively, add a `SubscribeWithPoll(projection, interval)` that returns a channel that also receives periodic ticks — letting each subscriber choose their own fallback interval. ### PGChangeRelay Add to constructor or options: ```go type PGChangeRelayOption func(*PGChangeRelay) func WithReconnectDelay(d time.Duration) PGChangeRelayOption func WithBroadcastTimeout(d time.Duration) PGChangeRelayOption ``` Defaults: reconnect 1s, broadcast 2s. ### ChannelEventBus Add option: ```go func WithChannelBufferSize(size int) ChannelEventBusOption ``` Default: 256. ## Requirements - All current constants become defaults - Options pattern for configuration (consistent with rest of eskit) - Godoc on every option explaining what it does and the default value - Tests for custom values - Benchmarks for any hot-path changes - The SSE fallback poll is the most important addition here — it turns "permanently stale" into "at most N seconds stale" Related: subscription.Config already does this correctly — PollInterval, RetryBaseDelay, etc. are all configurable with defaults. Match that pattern.