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Update 分布式.md

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为 Paxos 示例和栅栏令牌各补一张时序图。
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CyC2018
2026-10-25 18:52:37 +08:00
parent 385df45164
commit c6c805e4f8
5 changed files with 138 additions and 0 deletions
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notes/pics/fencing-token.png
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notes/分布式.md
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@@ -89,6 +89,8 @@ Redis 8.4 新增了 `DELEX lock_key IFEQ unique_value` 指令，可以直接原
RedLock 依赖各个节点的时钟基本同步，并且无法应对进程暂停（例如 GC）导致锁过期后客户端仍然认为自己持有锁的情况，因此存在争议。更可靠的做法是让锁服务每次加锁时返回一个单调递增的栅栏令牌（Fencing Token），客户端访问资源时带上令牌，资源拒绝令牌比已处理过的更小的请求。
<div align="center"> <img src="pics/fencing-token.png" width="560px"/> </div><br>
### Zookeeper 的有序节点
#### 1. Zookeeper 抽象模型
@@ -332,6 +334,8 @@ Acceptor 接受一个提议之后，会将该提议发送给所有的 Learner。
- A 发送 Prepare(2)，X 和 Y 做出承诺并响应。A 得到大多数响应之后发送 Accept(2, 8)，X 和 Y 接受该提议，此时值 8 已经被选定；
- 之后 B 发送 Prepare(4)，它收到的大多数响应中至少有一个来自 X 或 Y，响应中包含已经接受过的提议 [2, 8]，因此 B 只能发送 Accept(4, 8)，而不能使用自己的提议值，从而保证了选定的值不会改变。
<div align="center"> <img src="pics/paxos-example.png" width="600px"/> </div><br>
### 约束条件
#### 1\. 正确性
tools/diagram/src/fencing-token.svg
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<style>
text { font-family: "PingFang SC", "Microsoft YaHei", Helvetica, Arial, sans-serif; fill: #666; font-size: 13px; }
.head { font-weight: bold; text-anchor: middle; }
.msg { text-anchor: middle; font-size: 12px; }
.note { font-size: 12px; fill: #C0605A; }
.ok { fill: #6A9F68; }
.title { font-weight: bold; font-size: 15px; fill: #777; text-anchor: middle; }
.life { stroke: #BBB; stroke-width: 1; stroke-dasharray: 4 4; }
.arrow { stroke: #666; stroke-width: 1.3; fill: none; marker-end: url(#a); }
.reply { stroke-dasharray: 5 4; }
.lost { stroke: #C0605A; marker-end: url(#x); }
.shadow { fill: #C0C0C0; }
</style>
<defs>
<marker id="a" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto">
<path d="M1,1 L9,5 L1,9" fill="none" stroke="#666" stroke-width="1.6"/>
</marker>
<marker id="x" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto">
<path d="M1,1 L9,5 L1,9" fill="none" stroke="#C0605A" stroke-width="1.6"/>
</marker>
</defs>
<rect width="100%" height="100%" fill="#FFFFFF"/>
<text x="300" y="28" class="title">栅栏令牌</text>
<line x1="90" y1="76" x2="90" y2="428" class="life"/>
<line x1="230" y1="76" x2="230" y2="428" class="life"/>
<line x1="370" y1="76" x2="370" y2="428" class="life"/>
<line x1="510" y1="76" x2="510" y2="428" class="life"/>
<rect x="52" y="48" width="82" height="30" rx="6" class="shadow"/>
<rect x="49" y="45" width="82" height="30" rx="6" fill="#B0E3E6"/>
<text x="90" y="64.5" class="head">客户端 1</text>
<rect x="197" y="48" width="72" height="30" rx="6" class="shadow"/>
<rect x="194" y="45" width="72" height="30" rx="6" fill="#B1DDF0"/>
<text x="230" y="64.5" class="head">锁服务</text>
<rect x="332" y="48" width="82" height="30" rx="6" class="shadow"/>
<rect x="329" y="45" width="82" height="30" rx="6" fill="#B0E3E6"/>
<text x="370" y="64.5" class="head">客户端 2</text>
<rect x="477" y="48" width="72" height="30" rx="6" class="shadow"/>
<rect x="474" y="45" width="72" height="30" rx="6" fill="#B1DDF0"/>
<text x="510" y="64.5" class="head">存储</text>
<line x1="94" y1="100" x2="226" y2="100" class="arrow"/>
<text x="160" y="94" class="msg">获取锁</text>
<line x1="226" y1="134" x2="94" y2="134" class="arrow reply"/>
<text x="160" y="128" class="msg">成功，令牌 33</text>
<rect x="85" y="158" width="10" height="150" fill="#F3D9A4" stroke="#D9B44A"/>
<text x="102" y="237" class="note"></text>
<text x="78" y="172" class="note" text-anchor="end">GC 停顿</text>
<text x="240" y="206" class="note" text-anchor="start">锁过期</text>
<line x1="366" y1="236" x2="234" y2="236" class="arrow"/>
<text x="300" y="230" class="msg">获取锁</text>
<line x1="234" y1="270" x2="366" y2="270" class="arrow reply"/>
<text x="300" y="264" class="msg">成功，令牌 34</text>
<line x1="374" y1="304" x2="506" y2="304" class="arrow"/>
<text x="440" y="298" class="msg">写入，令牌 34</text>
<text x="500" y="342" class="note ok" text-anchor="end">接受，记录 34</text>
<line x1="94" y1="372" x2="506" y2="372" class="arrow"/>
<text x="140" y="366" class="msg">写入，令牌 33</text>
<text x="500" y="410" class="note" text-anchor="end">拒绝，33 &lt; 34</text>
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tools/diagram/src/paxos-example.svg
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<style>
text { font-family: "PingFang SC", "Microsoft YaHei", Helvetica, Arial, sans-serif; fill: #666; font-size: 13px; }
.head { font-weight: bold; text-anchor: middle; }
.msg { text-anchor: middle; font-size: 12px; }
.note { font-size: 12px; fill: #C0605A; }
.ok { fill: #6A9F68; }
.title { font-weight: bold; font-size: 15px; fill: #777; text-anchor: middle; }
.life { stroke: #BBB; stroke-width: 1; stroke-dasharray: 4 4; }
.arrow { stroke: #666; stroke-width: 1.3; fill: none; marker-end: url(#a); }
.reply { stroke-dasharray: 5 4; }
.lost { stroke: #C0605A; marker-end: url(#x); }
.shadow { fill: #C0C0C0; }
</style>
<defs>
<marker id="a" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto">
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</marker>
<marker id="x" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto">
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</marker>
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<text x="320" y="28" class="title">Paxos 示例</text>
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<text x="64" y="64.5" class="head">Proposer A</text>
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<text x="192" y="64.5" class="head">Acceptor X</text>
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<text x="320" y="64.5" class="head">Acceptor Y</text>
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<rect x="396" y="45" width="104" height="30" rx="6" fill="#B1DDF0"/>
<text x="448" y="64.5" class="head">Acceptor Z</text>
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<rect x="524" y="45" width="104" height="30" rx="6" fill="#B0E3E6"/>
<text x="576" y="64.5" class="head">Proposer B</text>
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<text x="128" y="94" class="msg">Prepare(2)</text>
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<text x="240" y="124" class="msg">Prepare(2)</text>
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<text x="240" y="184" class="msg">承诺</text>
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<text x="128" y="214" class="msg">Accept(2, 8)</text>
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<text x="240" y="244" class="msg">Accept(2, 8)</text>
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<text x="128" y="274" class="msg">接受</text>
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<text x="240" y="304" class="msg">接受</text>
<text x="320" y="344" class="note ok" text-anchor="middle">X、Y 构成多数派，值 8 已被选定</text>
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<text x="512" y="364" class="msg">Prepare(4)</text>
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<text x="400" y="394" class="msg">Prepare(4)</text>
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<text x="512" y="424" class="msg">承诺</text>
<line x1="324" y1="460" x2="572" y2="460" class="arrow reply"/>
<text x="400" y="454" class="msg">承诺，已接受 [2, 8]</text>
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<text x="512" y="484" class="msg">Accept(4, 8)</text>
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<text x="400" y="514" class="msg">Accept(4, 8)</text>
<text x="320" y="554" class="note" text-anchor="middle">B 只能沿用值 8，不能使用自己的提议值</text>
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