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document-haness/docs/clean-architecture-backend-template/tech-log-studio/state-machines-and-ownership/concept/concept-messaging-schema-avro-c06.md
T
DongHyeonkaandClaude Opus 5 b2963105a8 docs(keycloak-session-store): import the session-storage lab as a new project
The keycloak project ended with four open questions that design could not
settle. A two-VM lab was built to answer them by measurement, and this is
that material: 26 experiments, 125 raw command outputs, 22 browser captures.

Follows the import procedure in README.md.

  source/     the originating repository verbatim — 78 documents, 28 SVGs,
              8 manifests, plus .source-revision recording the commit
  final/      the SSOT
    document.md   729 lines written from the 29 experiment documents, not
                  concatenated: what was predicted, what was measured, and
                  where the measurement itself was wrong
    evidence/raw    125 outputs, flattened to <experiment>__<file> because
                    the originals collided (01-baseline.txt appeared three
                    times) and the audit only globs the top level
    evidence/meta   one per raw file; command and exitCode are null and the
                    README says why rather than inventing them
    evidence/browser  22 captures
    assets/       three diagrams through techviz
    .techviz/     their VizSpecs

A separate project rather than an addition to keycloak: the B-layer answers
that project's four questions, but the A, C and D layers are about cluster
failure, SSO and operations, and one document.md should hold one subject.
The four question records there can point here through 관계.

Recorded rather than papered over: only three of the 28 diagrams were
remade. The repository forbids hand-drawn SVG and forbids titles inside the
canvas; all 28 originals carry both, so converting them is redrawing, not
reformatting. They stay in source/ and the gap is written into the document.

verify-pipeline.py passes. audit-records.py reports no issues.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 22:51:59 +09:00

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---
kind: CONCEPT
slug: messaging-schema-avro-c06
title: 재사용 자리에 항상 null을 넘겨 공유 상태를 없앤다
topic: state-machines-and-ownership
project: clean-architecture-backend-template
status: 게시 전
sourceRevision: 21234e38cdb9a926cbc92bb97a2aee2e4a7d2916
rootTreeNode: concept:messaging-schema-avro-c06
evidenceCapturedOn: 2026-09-01
assets:
- key: messaging-schema-avro-c06
file: ../../../final/evidence/rendered/messaging-schema-avro-c06.svg
evidence:
- ../../../final/evidence/raw/messaging-schema-avro-c06.txt
source:
- 원본 분석 절은 analysis/messaging/messaging-schema-avro.md#L298 이다.
module: messaging-schema-avro
---
# 재사용 자리에 항상 null을 넘겨 공유 상태를 없앤다
`AvroMessageCodec`은 불변이고, 인코더·디코더·sink가 전부 호출마다 새로 만들어진다.
## 관계
- **모드 enum을 분기 조건으로 쓰면 각 분기에 테스트를 둔다**
같은 분석 리프에서 끌어낸 규칙이다.
- **컬렉션 순서가 계약이면 양쪽에서 같은 방향으로 적는다**
같은 분석 리프에서 끌어낸 규칙이다.
- **안정 코드는 판단 단위로 정하고 구현 단위로 정하지 않는다**
같은 분석 리프에서 끌어낸 규칙이다.
## 본문
<!-- body:start -->
`AvroMessageCodec`은 불변이다 — `schemas``Map.copyOf`된 평탄 맵, `maxBytes`는 int. `BoundedByteSink`·`BinaryEncoder`·`DatumReader`·`BinaryDecoder`는 전부 호출마다 새로 만들어진다.
## AvroMessageCodec 참조 위치
:::evidence key="messaging-schema-avro-c06" alt="코드베이스에서 AvroMessageCodec 를 검색한 출력 21줄. 이 기록이 세는 참조가 그 출력에 그대로 보인다." caption="AvroMessageCodec 코드베이스 검색 — 21줄 · exit 0" zoom="true"
:::
## 재사용 자리에 항상 null을 넘긴다
`EncoderFactory.get()`/`DecoderFactory.get()`은 Avro의 싱글턴 팩토리이고 스레드 안전하다. 다만 `binaryDecoder(encoded, null)`의 두 번째 인자가 재사용 decoder 자리인데 항상 `null`을 넘긴다 — 재사용하지 않으므로 공유 상태가 없다. 성능을 버리고 안전을 택한 형태다. `AvroCompatibilityGate`는 상태가 없다.
<!-- body:end -->