https://linzeyan.github.io/categories/design/Recent content in Design on RickyHugo -- gohugo.ioenTue, 18 Apr 2023 13:58:38 +0800https://linzeyan.github.io/posts/2023/20230418-software-design-principles/Tue, 18 Apr 2023 13:58:38 +0800https://linzeyan.github.io/posts/2023/20230418-software-design-principles/<ul> <li><a href="https://coolshell.cn/articles/4535.html" target="_blank" rel="noopener">Some Software Design Principles</a></li> </ul> <h3 id="1-dont-repeat-yourself-dry">1. Don&rsquo;t Repeat Yourself (DRY)</h3> <h3 id="2-keep-it-simple-stupid-kiss">2. Keep It Simple, Stupid (KISS)</h3> <p>Making something complex is easy, but making something complex simple is difficult.</p> <h3 id="3-program-to-an-interface-not-an-implementation">3. Program to an interface, not an implementation</h3> <ol> <li>Prefer composition over inheritance</li> <li>Dependency inversion principle</li> </ol> <h3 id="4-command-query-separation-cqs">4. Command-Query Separation (CQS)</h3> <ul> <li>Query: when a method returns a value to answer a question</li> <li>Command: when a method changes the state of an object</li> </ul> <h3 id="5-you-aint-gonna-need-it-yagni">5. You Ain&rsquo;t Gonna Need It (YAGNI)</h3> <p>Only design and implement what is necessary. Avoid overengineering. Implement what you need now; add more when needed later.</p>https://linzeyan.github.io/posts/2023/20230418-high-availability-system/Tue, 18 Apr 2023 10:24:00 +0800https://linzeyan.github.io/posts/2023/20230418-high-availability-system/<ul> <li><a href="https://coolshell.cn/articles/17459.html" target="_blank" rel="noopener">On High Availability Systems</a></li> </ul> <table> <thead> <tr> <th>Item / Mechanism</th> <th>Backups</th> <th>M/S</th> <th>MM</th> <th>2PC</th> <th>Paxos</th> </tr> </thead> <tbody> <tr> <td>Consistency</td> <td>Weak</td> <td>Eventual</td> <td>Eventual</td> <td>Strong</td> <td>Strong</td> </tr> <tr> <td>Transactions</td> <td>No</td> <td>Full</td> <td>Local</td> <td>Full</td> <td>Full</td> </tr> <tr> <td>Latency</td> <td>Low</td> <td>Low</td> <td>Low</td> <td>High</td> <td>High</td> </tr> <tr> <td>Throughput</td> <td>High</td> <td>High</td> <td>High</td> <td>Low</td> <td>Medium</td> </tr> <tr> <td>Data loss</td> <td>Lots</td> <td>Some</td> <td>Some</td> <td>None</td> <td>None</td> </tr> <tr> <td>Failover</td> <td>Down</td> <td>Read only</td> <td>Read only</td> <td>Read/write</td> <td>Read/write</td> </tr> </tbody> </table> <p>This table essentially covers the foundational solutions for high-availability systems today. M/S and MM are not hard to implement, but have many issues. 2PC suffers from poor performance, while Paxos is too complex and difficult to implement.</p>