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fix(rest): set Vary: Accept-Encoding on GzipMiddleware responses #229

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Merged
SyniRon merged 2 commits into from
Jun 30, 2026
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Merged

fix(rest): set Vary: Accept-Encoding on GzipMiddleware responses #229

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edabc99
fix(rest): set Vary: Accept-Encoding on GzipMiddleware responses
SyniRon Jun 30, 2026
befcad8
fix(rest): correct Vary comment direction and document it on error re…
SyniRon Jun 30, 2026
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8 changes: 8 additions & 0 deletions contract/spec_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -739,6 +739,14 @@ func TestSpec_MutationCanary(t *testing.T) {
const ranks200Block = ` "200":
description: Rank reference list.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down
145 changes: 145 additions & 0 deletions openapi/openapi.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,14 @@ paths:
"200":
description: The full milpac profile.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -115,6 +123,14 @@ paths:
"200":
description: The full milpac profile.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -150,6 +166,14 @@ paths:
"200":
description: The full milpac profile.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -185,6 +209,14 @@ paths:
"200":
description: The full milpac profile.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -216,6 +248,14 @@ paths:
"200":
description: Profiles keyed by milpac relation id.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -251,6 +291,14 @@ paths:
"200":
description: Lite profiles keyed by milpac relation id.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -284,6 +332,14 @@ paths:
"200":
description: S1 uniforms profiles keyed by milpac relation id.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -336,6 +392,14 @@ paths:
Matching lite profiles keyed by milpac relation id; {} when
nothing matches (200, never 404).
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -365,6 +429,14 @@ paths:
"200":
description: Rank reference list.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -394,6 +466,14 @@ paths:
"200":
description: Position group reference tree.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -421,6 +501,14 @@ paths:
"200":
description: AWOL list.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -453,6 +541,14 @@ paths:
"200":
description: Forum group directory.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: data may be up to 10 minutes stale.
Expand Down Expand Up @@ -576,6 +672,14 @@ paths:
"200":
description: One page of tickets.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: always served live. Responses are
Expand Down Expand Up @@ -617,6 +721,14 @@ paths:
"200":
description: The ticket with its first messages.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: always served live. Responses are
Expand Down Expand Up @@ -655,6 +767,14 @@ paths:
"200":
description: The ticket with its first messages.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: always served live. Responses are
Expand Down Expand Up @@ -715,6 +835,14 @@ paths:
"200":
description: One page of the message thread.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: always served live. Responses are
Expand Down Expand Up @@ -745,6 +873,14 @@ paths:
"200":
description: Category reference tree.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
Cache-Control:
description: >-
Freshness signal: always served live. Responses are
Expand Down Expand Up @@ -826,6 +962,15 @@ components:
JSON error body. `code` is a numeric status code (3 InvalidArgument →
400, 5 NotFound → 404, 7 PermissionDenied → 403, 13 Internal → 500).
`message` is a human-readable description of the failure.
headers:
Vary:
description: >-
Cache-keying hint: the server selects the body encoding from
Accept-Encoding, so a shared cache must store the gzip and
identity variants under separate keys.
schema:
type: string
const: Accept-Encoding
content:
application/json:
schema:
Expand Down
11 changes: 11 additions & 0 deletions rest/gzip.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,17 @@ import (
// closed.
func GzipMiddleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// The response body is selected by proactive content negotiation on
// Accept-Encoding, so declare that to any shared cache: it must key each
// encoding variant separately rather than serve one body for both.
// Applied unconditionally, before the branch, so every response that
// reaches this layer inherits it (the outer auth 401 short-circuits
// before it) — the gzip branch and the identity pass-through alike, and
// every status, including the bodyless 204/304 finals (Vary is a
// cache-keying hint, so it is correct to keep there, unlike the
// Content-Encoding stripped off them below). Add, not Set, so a Vary
// value already set by an outer layer survives — Set would drop it.
w.Header().Add("Vary", "Accept-Encoding")
if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
w.Header().Set("Content-Encoding", "gzip")
gz := gzip.NewWriter(w)
Expand Down
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