54 lines
2.5 KiB
Markdown
54 lines
2.5 KiB
Markdown
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# ADR-001: Direct logz Import for Context Helpers (Exception to Global ADR-001)
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**Status:** Accepted
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**Date:** 2026-03-18
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## Context
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Global ADR-001 states that modules receiving a logger from the application layer
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should duck-type the logger injection point with a private interface (e.g.
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`type Logger interface { Info(...); Error(...) }`), so the application is not forced
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to import `logz` just to satisfy a concrete type.
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`httpmw` follows this rule for its `Logger` interface in `logger.go`. Any struct
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with the right method set satisfies it.
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However, `httpmw` also calls `logz.WithRequestID` (in `requestid.go`) and
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`logz.GetRequestID` (in `logger.go`) to store and read the request ID from context.
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These functions use an **unexported context key type** defined inside `logz`:
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```go
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// inside logz — not exported
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type contextKey string
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const requestIDKey contextKey = "request_id"
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```
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A context value stored with that key can only be read back with the same key. If
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`httpmw` tried to replicate the storage using its own unexported key, the values set
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by `logz.WithRequestID` would be invisible to `logz.GetRequestID`, and vice-versa —
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breaking the downstream `logz.Logger.WithContext` integration.
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## Decision
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`httpmw` imports `logz` directly for context helper access (`logz.WithRequestID`,
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`logz.GetRequestID`). This is an **explicit, documented exception** to the
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duck-typed Logger rule in global ADR-001.
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The Logger injection point remains duck-typed (`httpmw.Logger` interface in
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`logger.go`). The exception applies only to the two context functions, not to the
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logger parameter of `RequestLogger`.
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## Consequences
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- `httpmw` has a direct module dependency on `logz` in its `go.mod`. Upgrading
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`logz` is a breaking change for `httpmw` if the context helper signatures change.
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- `logz.WithRequestID` and `logz.GetRequestID` form a shared context contract
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between `httpmw` (which stores the ID) and `logz.Logger` (which reads it when
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enriching log records). Both sides of the contract must be the same package.
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- Applications that use `httpmw` without `logz` as their logger will still get
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request IDs injected into the context correctly — `RequestID` middleware works
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independently. The ID simply won't be picked up automatically by a non-logz logger.
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- This exception must not be used as a precedent for importing logz elsewhere without
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justification. The rule remains: duck-type logger injection; import logz only when
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the unexported context key contract requires it.
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