<!doctype html> <html> <head> <meta charset="utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1" /> <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/github-markdown-css/5.5.1/github-markdown.min.css" /> <title>haunt98 posts</title> </head> <style> .markdown-body { box-sizing: border-box; min-width: 200px; max-width: 980px; margin: 0 auto; padding: 45px; font-family: Shantell Sans Normal, Rec Mono Casual, SF Pro, Inter, sans-serif; font-weight: 500; } .markdown-body pre { font-family: Berkeley Mono, IBM Plex Mono, SF Mono, Jetbrains Mono, monospace; } @media (max-width: 767px) { .markdown-body { padding: 15px; } } </style> <body class="markdown-body"> <h2> <a href="index.html"><code>~</code></a> </h2> <div class="markdown-heading"> <h1 class="heading-element">Reload config</h1> <a id="user-content-reload-config" class="anchor" aria-label="Permalink: Reload config" href="#reload-config" ><span aria-hidden="true" class="octicon octicon-link"></span ></a> </div> <p>This serves as design draft of reload config system</p> <div class="highlight highlight-source-wsd"> <pre><span class="pl-k">@startuml</span> Reload config <span class="pl-k">skinparam</span> <span class="pl-k">defaultFontName</span> <span class="pl-s">Iosevka Term SS08</span> <span class="pl-k">participant</span> <span class="pl-c1">admin</span> <span class="pl-k">participant</span> <span class="pl-c1">other_service</span> <span class="pl-k">participant</span> <span class="pl-c1">config_service</span> <span class="pl-k">participant</span> <span class="pl-c1">storage</span> <span class="pl-k">==</span> <span class="pl-s">Admin handle</span> <span class="pl-k">==</span> <span class="pl-c1">admin</span> <span class="pl-k">-></span> <span class="pl-c1">config_service</span>: set/update/delete config <span class="pl-c1">config_service</span> <span class="pl-k">-></span> <span class="pl-c1">storage</span>: set/update/delete config <span class="pl-k">==</span> <span class="pl-s">Other service handle</span> <span class="pl-k">==</span> <span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: init service <span class="pl-k">activate</span> <span class="pl-c1">other_service</span> <span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">storage</span>: make connection <span class="pl-k">loop</span> <span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">storage</span>: listen on config change <span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: save config to memory <span class="pl-k">end</span> <span class="pl-k">deactivate</span> <span class="pl-c1">other_service</span> <span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: do business <span class="pl-k">activate</span> <span class="pl-c1">other_service</span> <span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: get config <span class="pl-c1">other_service</span> <span class="pl-k">-></span> <span class="pl-c1">other_service</span>: do other business <span class="pl-k">deactivate</span> <span class="pl-c1">other_service</span> <span class="pl-k">@enduml</span></pre> </div> <p> Config storage can be any key value storage or database like etcd, Consul, mySQL, ... </p> <p> If storage is key value storage, maybe there is API to listen on config change. Otherwise we should create a loop to get all config from storage for some interval, for example each 5 minute. </p> <p> Each <code>other_service</code> need to get config from its memory, not hit <code>storage</code>. 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> <p>Pros:</p> <ul> <li> <p> Config can be dynamic, service does not need to restart to apply new config. </p> </li> <li> <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> </li> </ul> <p>Cons:</p> <ul> <li>Each service has 1 more dependency, aka <code>storage</code>.</li> <li> Need to handle fallback config, incase <code>storage</code> failure. </li> <li>Delay between upstream/downstream config</li> </ul> <div> Feel free to ask me via <a href="mailto:hauvipapro+posts@gmail.com">email</a> or <a rel="me" href="https://hachyderm.io/@haunguyen">Mastodon</a>. <br />Source code is available on <a href="https://github.com/haunt98/posts-go">GitHub</a> <a href="https://codeberg.org/yoshie/posts-go">Codeberg</a> <a href="https://git.sr.ht/~youngyoshie/posts-go">sourcehut</a> <a href="https://gitea.treehouse.systems/yoshie/posts-go">Treehouse</a> <a href="https://gitlab.com/youngyoshie/posts-go">GitLab</a> </div> </body> </html>