Microservice architecture—graceful shutdown solution

Abstract: Graceful application shutdown in microservice architecture mainly refers to the planned and smooth exit of application instances (that is, no incidents that need to be handled).

1 Introduction

Graceful application shutdown in microservice architecture mainly refers to the planned and smooth exit of application instances (that is, no incidents that need to be handled). Application server shutdowns are mainly divided into two categories: active shutdowns and passive shutdowns, of which active shutdowns and most passive shutdowns can achieve graceful shutdowns. If the application does not shut down gracefully, the following situations will occur:

• Data loss: The data in the memory has not been persisted to the disk
• File corruption: The file being written has not been updated, resulting in file corruption
• Request lost: The request waiting in the queue is lost
• Response lost: The successful transaction has not had time to respond
• Transaction interruption: Transactions that are being processed to an intermediate state are forcibly interrupted
• The service is not offline: the upstream service will still continue to send consumption requests to the downstream service

The goal of the elegant upgrade of our microservices is to avoid the above situations, thereby avoiding the workload of manual intervention and improving the service reliability of the microservice architecture.

2 Usage scenarios

Graceful shutdown can solve the following scenarios:

• KILL PID
• The application automatically exited unexpectedly (System.exit(n))
• Use script command to stop the application

Graceful shutdown cannot solve the following scenarios:

• Sudden power outage
• Machine physical destruction
• KILL-9 PID or taskkill /f /pid

3 ShutdownHook

Java's graceful shutdown is usually achieved by registering the JDK's ShutdownHook (hook). When the system receives the exit command, it first marks the system as being in the exit state and will no longer receive new messages, then processes the backlog of messages, and finally calls resources The recycling interface destroys the resources, and finally each thread exits execution. A simple demo case is as follows (simple version):

 <span class="hljs-comment">/**
 * 优雅停机处理方式
 * 
 * <span class="hljs-doctag">@author</span> lry
 **/</span>
<span class="hljs-keyword"><span class="hljs-selector-tag">public</span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-selector-tag">class</span></span> <span class="hljs-title"><span class="hljs-selector-tag">Main</span></span></span>{

    <span class="hljs-comment">/**
     * 启动应用
     **/</span>
    <span class="hljs-function"><span class="hljs-keyword"><span class="hljs-selector-tag">public</span></span> <span class="hljs-keyword"><span class="hljs-selector-tag">void</span></span> <span class="hljs-title"><span class="hljs-selector-tag">start</span></span><span class="hljs-params">()</span></span>{
        <span class="hljs-comment">// 第一步：启动应用服务……</span>

        <span class="hljs-comment">// 第二步：注册JDK钩子</span>
        <span class="hljs-selector-tag">Runtime</span><span class="hljs-selector-class">.getRuntime</span>()<span class="hljs-selector-class">.addShutdownHook</span>(<span class="hljs-keyword">new</span> Thread(<span class="hljs-keyword">new</span> Runnable() {
            <span class="hljs-meta"><span class="hljs-variable">@Override</span></span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">run</span><span class="hljs-params">()</span> </span>{
                System.out.println(<span class="hljs-string">"The hook running..."</span>);
                <span class="hljs-comment">//第三步：调用停机处理</span>
                stop();
            }
        }));
    }

    <span class="hljs-comment">/**
     * 停止应用
     **/</span>
    <span class="hljs-function"><span class="hljs-keyword"><span class="hljs-selector-tag">public</span></span> <span class="hljs-keyword"><span class="hljs-selector-tag">void</span></span> <span class="hljs-title"><span class="hljs-selector-tag">stop</span></span><span class="hljs-params">()</span></span>{
        <span class="hljs-comment">// 停止应用前停机处理(如：注销服务、标记不接受请求等)</span>
    }

}

Timeout control
Usually, graceful exit requires a timeout control mechanism. If the resource recovery and other operations before exit are not completed before the timeout period is reached, the shutdown script directly calls KILL -9 PID to force the exit. Otherwise, it may wait for a long time.

4 Microservices shut down gracefully

Tiada penyelesaian bersatu untuk penutupan perkhidmatan mikro yang anggun. Hanya faham idea dan reka bentuk teras:
Saliran → Sekat → Menunggu penutupan

Tetapi dalam seni bina perkhidmatan mikro, kami boleh mengikut peraturan yang disyorkan berikut untuk mereka bentuk mekanisme penutupan yang anggun untuk perkhidmatan mikro:

• Semua aplikasi perkhidmatan mikro harus menyokong penutupan yang anggun
• Utamakan pembatalan pendaftaran contoh perkhidmatan yang didaftarkan di pusat pendaftaran
• Titik capaian aplikasi perkhidmatan yang akan diturunkan ditandakan sebagai penafian perkhidmatan
• Perkhidmatan huluan menyokong kegagalan perkhidmatan yang dinafikan kerana gangguan yang anggun
• Antara muka penutupan yang sesuai juga disediakan mengikut perniagaan tertentu

Masa henti aplikasi mikroperkhidmatan yang anggun terbahagi terutamanya kepada dua jenis mengikut peranan pengguna yang berbeza:

• • Reka bentuk penutupan yang elegan untuk aplikasi perniagaan perkhidmatan mikro:

• • Reka bentuk penutupan yang elegan untuk aplikasi perniagaan perkhidmatan mikro
  • Reka bentuk penutupan anggun aplikasi gerbang perkhidmatan mikro:

Reka bentuk penutupan anggun aplikasi gerbang perkhidmatan mikro

Penutupan rapi lapisan peralatan lain boleh diperolehi daripada dua jenis penyelesaian di atas, seperti:

• Naik taraf keseluruhan seni bina bahagian belakang, anda boleh bertukar terus daripada DNS atau Nginx
• Naik taraf lapisan Nginx, anda boleh bertukar terus daripada DNS

5 kes penggunaan

Antara produk sumber terbuka dalam industri, banyak produk menggunakan cangkuk JDK untuk mencapai penutupan yang anggun, seperti produk berikut:

• Berjaring
• DUBBO

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