【解决】Error: ENOSPC: no space left on device, watch

发现问题：

启动 node 项目ReactNative时候出现报错Error: ENOSPC: no space left on device, watch

[root@iz2zeihk6kfcls5kwmqzj1z JFReactNativeProject]# npm start

> wk_rn@0.0.1 start /app/jenkins_workspace/workspace/JFReactNativeProject
> react-native start

┌──────────────────────────────────────────────────────────────────────────────┐
│                                                                              │
│  Running Metro Bundler on port 8081.                                         │
│                                                                              │
│  Keep Metro running while developing on any JS projects. Feel free to        │
│  close this tab and run your own Metro instance if you prefer.               │
│                                                                              │
│  https://github.com/facebook/react-native                                    │
│                                                                              │
└──────────────────────────────────────────────────────────────────────────────┘

Looking for JS files in
   /app/jenkins_workspace/workspace/JFReactNativeProject

Loading dependency graph...fs.js:1413
    throw error;
    ^

Error: ENOSPC: no space left on device, watch '/app/jenkins_workspace/workspace/JFReactNativeProject/node_modules/.staging/react-native-ddd311e5/ReactAndroid/src/androidTest/java/com/facebook/react/testing/idledetection'
    at FSWatcher.start (fs.js:1407:26)
    at Object.fs.watch (fs.js:1444:11)
    at NodeWatcher.watchdir (/app/jenkins_workspace/workspace/JFReactNativeProject/node_modules/_sane@4.1.0@sane/src/node_watcher.js:159:22)
    at Walker.<anonymous> (/app/jenkins_workspace/workspace/JFReactNativeProject/node_modules/_sane@4.1.0@sane/src/common.js:109:31)
    at Walker.emit (events.js:182:13)
    at /app/jenkins_workspace/workspace/JFReactNativeProject/node_modules/_walker@1.0.7@walker/lib/walker.js:69:16
    at go$readdir$cb (/app/jenkins_workspace/workspace/JFReactNativeProject/node_modules/_graceful-fs@4.2.2@graceful-fs/graceful-fs.js:187:14)
    at FSReqWrap.oncomplete (fs.js:169:20)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! wk_rn@0.0.1 start: `react-native start`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the wk_rn@0.0.1 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /root/.npm/_logs/2019-09-25T06_57_58_754Z-debug.log

解决办法：

ENOSPC的含义是 Error No more hard-disk space available（没有更多的磁盘空间可以使用）

首先使用df -hT发现磁盘空间还有很多

然后从报错日志中发现FSWatcher和Object.fs.watch字段，然后查看系统允许用户监听文件数相关内容

#表示同一用户同时可以添加的watch数目（watch一般是针对目录，决定了同时同一用户可以监控的目录数量）
[root@iz2zeihk6kfcls5kwmqzj1z JFReactNativeProject]# cat /proc/sys/fs/inotify/max_user_watches
8192
[root@iz2zeihk6kfcls5kwmqzj1z JFReactNativeProject]# echo 100000 > /proc/sys/fs/inotify/max_user_watches
[root@iz2zeihk6kfcls5kwmqzj1z JFReactNativeProject]# cat /proc/sys/fs/inotify/max_user_watches
100000

永久生效方法如下：（建议采用此方法）

vim /etc/sysctl.conf
fs.inotify.max_user_watches = 100000（后面值根据实际情况可自行调整）
添加并运行/sbin/sysctl -p即可

启动验证：

再次启动，正常

[root@iz2zeihk6kfcls5kwmqzj1z JFReactNativeProject]# npm start

> wk_rn@0.0.1 start /app/jenkins_workspace/workspace/JFReactNativeProject
> react-native start

┌──────────────────────────────────────────────────────────────────────────────┐
│                                                                              │
│  Running Metro Bundler on port 8081.                                         │
│                                                                              │
│  Keep Metro running while developing on any JS projects. Feel free to        │
│  close this tab and run your own Metro instance if you prefer.               │
│                                                                              │
│  https://github.com/facebook/react-native                                    │
│                                                                              │
└──────────────────────────────────────────────────────────────────────────────┘

Looking for JS files in
   /app/jenkins_workspace/workspace/JFReactNativeProject

Loading dependency graph, done.

知识点：

inotify 的默认内核参数

• /proc/sys/fs/inotify/max_queued_events 默认值: 16384 该文件中的值为调用inotify_init时分配给inotify instance中可排队的event的数目的最大值，超出这个值得事件被丢弃，但会触发IN_Q_OVERFLOW事件
• /proc/sys/fs/inotify/max_user_instances 默认值: 128 指定了每一个real user ID可创建的inotify instatnces的数量上限
• /proc/sys/fs/inotify/max_user_watches 默认值: 8192 指定了每个inotify instance相关联的watches的上限

注意: max_queued_events 是 Inotify 管理的队列的最大长度，文件系统变化越频繁，这个值就应该越大

如果你在日志中看到Event Queue Overflow，说明 max_queued_events 太小需要调整参数后再次使用.