mirror of
https://github.com/microsoft/BCQuality.git
synced 2026-08-06 17:36:53 +01:00
0540c7bf6e
The 35 articles still in their seed form previously carried a banner reading "Seed article. ... Domain stewards should expand, restructure, and refine as needed." For a community preview, that phrasing reads as "TODO left in production" to first-time visitors. Replace all three banner variants (performance-seeded, security-seeded, community-ported) with a single positive invitation: > Contributions welcome — open a PR to refine or extend this article. Content and structure of the articles are unchanged; only the leading quote block differs. Articles that had their banner fully stripped in the earlier triage pass (the showcase-grade ten) are unaffected.
28 lines
1.6 KiB
Markdown
28 lines
1.6 KiB
Markdown
---
|
|
bc-version: [all]
|
|
domain: performance
|
|
keywords: [singleinstance, subscriber, event, memory, session]
|
|
technologies: [al]
|
|
countries: [w1]
|
|
application-area: [all]
|
|
---
|
|
|
|
# Avoid growing globals in SingleInstance subscribers
|
|
|
|
> Contributions welcome — open a PR to refine or extend this article.
|
|
|
|
## Description
|
|
|
|
A codeunit with `SingleInstance = true` is allocated once per session and lives until the session ends. Global variables on it are never collected between event fires. A subscriber that accumulates data into a global — buffering payloads, appending to a list, caching without a cap — steadily grows its session footprint for the entire user session. The symptom is memory that only recovers on sign-out, and it surfaces only on long-running sessions.
|
|
|
|
## Best Practice
|
|
|
|
Keep the global footprint on a SingleInstance subscriber bounded and intentional: a handful of flags, a setup record, a bounded cache with a maximum size. When cross-event state is genuinely needed, define an explicit reset point — end of a business process, arrival of a specific terminal event — that clears the growing collection.
|
|
|
|
See sample: `avoid-growing-globals-in-singleinstance-subscribers.good.al`.
|
|
|
|
## Anti Pattern
|
|
|
|
A SingleInstance subscriber that appends each event's payload to a global list, dictionary, or temporary record without a cap or cleanup trigger. The list grows for hours, memory pressure builds quietly, and debugging the root cause on a live environment is substantially harder than noticing the unbounded append in code review.
|
|
|
|
See sample: `avoid-growing-globals-in-singleinstance-subscribers.bad.al`.
|