102 lines
4.4 KiB
HTML
102 lines
4.4 KiB
HTML
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<body class="markdown-body">
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<a href="index">Index</a>
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<h1><a id="user-content-reload-config" class="anchor" aria-hidden="true" href="#reload-config"><span aria-hidden="true" class="octicon octicon-link"></span></a>Reload config</h1>
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<p>This serves as design draft of reload config system</p>
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<div class="highlight highlight-source-wsd"><pre><span class="pl-k">@startuml</span> Reload config
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<span class="pl-k">skinparam</span> <span class="pl-k">defaultFontName</span> <span class="pl-s">Iosevka Term SS08</span>
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<span class="pl-k">participant</span> <span class="pl-c1">admin</span>
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<span class="pl-k">participant</span> <span class="pl-c1">other_service</span>
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<span class="pl-k">participant</span> <span class="pl-c1">config_service</span>
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<span class="pl-k">participant</span> <span class="pl-c1">storage</span>
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<span class="pl-k">==</span> <span class="pl-s">Admin handle</span> <span class="pl-k">==</span>
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<span class="pl-c1">admin</span> <span class="pl-k">-></span> <span class="pl-c1">config_service</span>: set/update/delete config
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<span class="pl-c1">config_service</span> <span class="pl-k">-></span> <span class="pl-c1">storage</span>: set/update/delete config
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<span class="pl-k">==</span> <span class="pl-s">Other service handle</span> <span class="pl-k">==</span>
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<span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: init service
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<span class="pl-k">activate</span> <span class="pl-c1">other_service</span>
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<span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">storage</span>: make connection
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<span class="pl-k">loop</span>
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<span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">storage</span>: listen on config change
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<span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: save config to memory
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<span class="pl-k">end</span>
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<span class="pl-k">deactivate</span> <span class="pl-c1">other_service</span>
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<span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: do business
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<span class="pl-k">activate</span> <span class="pl-c1">other_service</span>
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<span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: get config
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<span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: do other business
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<span class="pl-k">deactivate</span> <span class="pl-c1">other_service</span>
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<span class="pl-k">@enduml</span></pre></div>
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<p>Config storage can be any key value storage or database like etcd, Consul, mySQL, ...</p>
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<p>If storage is key value storage, maybe there is API to listen on config change.
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Otherwise we should create a loop to get all config from storage for some interval, for example each 5 minute.</p>
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<p>Each <code>other_service</code> need to get config from its memory, not hit <code>storage</code>.
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So there is some delay between upstream config (config in <code>storage</code>) and downstream config (config in <code>other_service</code>), but maybe we can forgive that delay (???).</p>
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<p>Pros:</p>
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<ul>
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<li>
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<p>Config can be dynamic, service does not need to restart to apply new config.</p>
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</li>
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<li>
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<p>Each service only keep 1 connection to <code>storage</code> to listen to config change, not hit <code>storage</code> for each request.</p>
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</li>
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</ul>
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<p>Cons:</p>
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<ul>
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<li>Each service has 1 more dependency, aka <code>storage</code>.</li>
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<li>Need to handle fallback config, incase <code>storage</code> failure.</li>
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<li>Delay between upstream/downstream config</li>
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</ul>
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<a href="mailto:hauvipapro+posts@gmail.com"
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>Feel free to ask me via email</a
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>
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<a rel="me" href="https://hachyderm.io/@haunguyen">Mastodon</a>
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