fix: use singleton PostHog client instead of per-request instantiation#186
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fix: use singleton PostHog client instead of per-request instantiation#186jakebromberg wants to merge 2 commits intomainfrom
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jakebromberg
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AyBruno
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Mar 8, 2026
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| import { PostHog } from 'posthog-node'; | ||
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| let postHogClient: PostHog | null = null; |
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Rather than keep the posHogClient in this mirror.middleware.ts file, I think it would be good future proofing to move it into its own file in the utils directory as a common module level singleton. This way, in the future as we implement features we have a dedicated place to reach out to posthog for feature flags.
A new PostHog client (with its own connection pool and flush interval) was created for every request. Moved to a module-level lazy singleton. Co-authored-by: Cursor <cursoragent@cursor.com>
Extracts getPostHogClient() into a dedicated module so it can be reused for feature flags and other PostHog features beyond the mirror middleware.
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Summary
createBackendMirrorMiddlewareinstantiated a newPostHogclient (with its own connection pool and flush interval) inside theres.once('finish', ...)callback on every request, then calledshutdown()on each one.getPostHogClient(). The client is created once on first use and reused for all subsequent requests. Removed the per-requestshutdown()call since the singleton persists for the process lifetime.mirror.posthog.test.tsthat mocksposthog-node, fires two request finish events, and asserts thePostHogconstructor is called exactly once.Test plan
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