nordisk/holger

.nornir/assets/replication-flow.svg

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  <text x="20" y="26" class="lbl" font-size="15" font-weight="700">Repository replication — read-from-source / write-to-dest, content-id idempotent</text>

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  <text x="105" y="90" class="lbl" text-anchor="middle" font-weight="700">SOURCE store</text>
  <text x="105" y="110" class="sub" text-anchor="middle">repo.list() → ids</text>
  <text x="105" y="126" class="sub" text-anchor="middle">repo.fetch(id) → bytes</text>
  <text x="105" y="142" class="sub" text-anchor="middle">read-only (never mutated)</text>

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  <text x="415" y="76" class="lbl" text-anchor="middle" font-weight="700">replicate_pairs()</text>
  <text x="415" y="98" class="sub" text-anchor="middle">for each source artifact:</text>
  <text x="415" y="114" class="sub" text-anchor="middle">cid = sha256(bytes)</text>
  <text x="415" y="130" class="sub" text-anchor="middle">dest.fetch(id) present</text>
  <text x="415" y="146" class="sub" text-anchor="middle">&amp; sha256 == cid ?</text>
  <text x="415" y="168" class="sub" text-anchor="middle">execute ⇒ dest.put()</text>

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  <text x="705" y="82" class="lbl" text-anchor="middle" font-weight="700">COPY → dest</text>
  <text x="705" y="99" class="sub" text-anchor="middle">absent / content differs</text>

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  <text x="705" y="150" class="lbl" text-anchor="middle" font-weight="700">SKIP</text>
  <text x="705" y="167" class="sub" text-anchor="middle">present by content id</text>

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  <text x="415" y="261" class="lbl" text-anchor="middle" font-weight="700">DESTINATION store</text>
  <text x="415" y="281" class="sub" text-anchor="middle">writable repos only</text>
  <text x="415" y="296" class="sub" text-anchor="middle">read-only ⇒ fail closed</text>
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  <text x="675" y="257" class="lbl" text-anchor="middle" font-weight="700">ReplicationReport</text>
  <text x="675" y="277" class="sub" text-anchor="middle">examined · copied · skipped</text>
  <text x="675" y="292" class="sub" text-anchor="middle">would_copy · failed · truncated</text>
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  <text x="20" y="345" class="sub">Idempotent: a re-run over an unchanged source copies nothing (every artifact SKIPs). Dry-run (default) writes nothing; --execute copies.</text>
  <text x="20" y="363" class="sub">Two surfaces, one engine: CLI `replicate --from --to` (two separate file stores) · gRPC `ReplicationService.Replicate` (two repos, one server).</text>
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