150 lines
3.2 KiB
Markdown
150 lines
3.2 KiB
Markdown
# 业务代码处理 SIGTERM 信号
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要实现优雅终止，首先业务代码得支持下优雅终止的逻辑，在业务代码里面处理下 `SIGTERM` 信号，一般主要逻辑就是"排水"，即等待存量的任务或连接完全结束，再退出进程。
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本文给出各种语言的代码示例。
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## shell
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```bash
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#!/bin/sh
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## Redirecting Filehanders
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ln -sf /proc/$$/fd/1 /log/stdout.log
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ln -sf /proc/$$/fd/2 /log/stderr.log
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## Pre execution handler
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pre_execution_handler() {
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## Pre Execution
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# TODO: put your pre execution steps here
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: # delete this nop
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}
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## Post execution handler
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post_execution_handler() {
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## Post Execution
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# TODO: put your post execution steps here
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: # delete this nop
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}
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## Sigterm Handler
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sigterm_handler() {
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if [ $pid -ne 0 ]; then
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# the above if statement is important because it ensures
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# that the application has already started. without it you
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# could attempt cleanup steps if the application failed to
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# start, causing errors.
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kill -15 "$pid"
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wait "$pid"
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post_execution_handler
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fi
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exit 143; # 128 + 15 -- SIGTERM
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}
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## Setup signal trap
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# on callback execute the specified handler
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trap 'sigterm_handler' SIGTERM
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## Initialization
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pre_execution_handler
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## Start Process
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# run process in background and record PID
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>/log/stdout.log 2>/log/stderr.log "$@" &
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pid="$!"
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# Application can log to stdout/stderr, /log/stdout.log or /log/stderr.log
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## Wait forever until app dies
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wait "$pid"
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return_code="$?"
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## Cleanup
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post_execution_handler
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# echo the return code of the application
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exit $return_code
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```
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## Go
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```go
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package main
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import (
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"fmt"
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"os"
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"os/signal"
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"syscall"
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)
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func main() {
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sigs := make(chan os.Signal, 1)
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done := make(chan bool, 1)
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//registers the channel
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signal.Notify(sigs, syscall.SIGTERM)
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go func() {
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sig := <-sigs
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fmt.Println("Caught SIGTERM, shutting down")
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// Finish any outstanding requests, then...
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done <- true
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}()
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fmt.Println("Starting application")
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// Main logic goes here
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<-done
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fmt.Println("exiting")
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}
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```
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## Python
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```python
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import signal, time, os
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def shutdown(signum, frame):
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print('Caught SIGTERM, shutting down')
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# Finish any outstanding requests, then...
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exit(0)
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if __name__ == '__main__':
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# Register handler
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signal.signal(signal.SIGTERM, shutdown)
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# Main logic goes here
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```
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## NodeJS
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```js
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process.on('SIGTERM', () => {
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console.log('The service is about to shut down!');
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// Finish any outstanding requests, then...
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process.exit(0);
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});
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```
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## Java
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```java
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import sun.misc.Signal;
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import sun.misc.SignalHandler;
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public class ExampleSignalHandler {
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public static void main(String... args) throws InterruptedException {
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final long start = System.nanoTime();
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Signal.handle(new Signal("TERM"), new SignalHandler() {
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public void handle(Signal sig) {
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System.out.format("\nProgram execution took %f seconds\n", (System.nanoTime() - start) / 1e9f);
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System.exit(0);
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}
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});
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int counter = 0;
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while(true) {
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System.out.println(counter++);
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Thread.sleep(500);
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}
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}
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}
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```
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