[7.x] fix(NA): log rotation watchers usage (#60956)

docs/setup/settings.asciidoc

@@ -200,7 +200,7 @@ that feature would not take any effect.
 
 `logging.rotate.everyBytes:`:: [experimental] *Default: 10485760* The maximum size of a log file (that is `not an exact` limit). After the
 limit is reached, a new log file is generated. The default size limit is 10485760 (10 MB) and
-this option should be in the range of 102400 (100KB) to 1073741824 (1GB).
+this option should be in the range of 1048576 (1 MB) to 1073741824 (1 GB).
 
 `logging.rotate.keepFiles:`:: [experimental] *Default: 7* The number of most recent rotated log files to keep
 on disk. Older files are deleted during log rotation. The default value is 7. The `logging.rotate.keepFiles`
@@ -210,7 +210,7 @@ option has to be in the range of 2 to 1024 files.
 the `logging.rotate.usePolling` is enabled. That option has to be in the range of 5000 to 3600000 milliseconds.
 
 `logging.rotate.usePolling:`:: [experimental] *Default: false* By default we try to understand the best way to monitoring
-the log file. However, there is some systems where it could not be always accurate. In those cases, if needed,
+the log file and warning about it. Please be aware there are some systems where watch api is not accurate. In those cases, in order to get the feature working,
 the `polling` method could be used enabling that option.
 
 `logging.silent:`:: *Default: false* Set the value of this setting to `true` to

src/legacy/server/config/schema.js

@@ -136,8 +136,8 @@ export default () =>
           .keys({
             enabled: Joi.boolean().default(false),
             everyBytes: Joi.number()
-              // > 100KB
-              .greater(102399)
+              // > 1MB
+              .greater(1048576)
               // < 1GB
               .less(1073741825)
               // 10MB

src/legacy/server/logging/rotate/log_rotator.test.ts

@@ -204,8 +204,8 @@ describe('LogRotator', () => {
     expect(logRotator.running).toBe(true);
     expect(logRotator.usePolling).toBe(false);
 
-    const usePolling = await logRotator._shouldUsePolling();
-    expect(usePolling).toBe(false);
+    const shouldUsePolling = await logRotator._shouldUsePolling();
+    expect(shouldUsePolling).toBe(false);
 
     await logRotator.stop();
   });
@@ -231,7 +231,8 @@ describe('LogRotator', () => {
     await logRotator.start();
 
     expect(logRotator.running).toBe(true);
-    expect(logRotator.usePolling).toBe(true);
+    expect(logRotator.usePolling).toBe(false);
+    expect(logRotator.shouldUsePolling).toBe(true);
 
     await logRotator.stop();
   });
@@ -257,7 +258,8 @@ describe('LogRotator', () => {
     await logRotator.start();
 
     expect(logRotator.running).toBe(true);
-    expect(logRotator.usePolling).toBe(true);
+    expect(logRotator.usePolling).toBe(false);
+    expect(logRotator.shouldUsePolling).toBe(true);
 
     await logRotator.stop();
     jest.useRealTimers();

src/legacy/server/logging/rotate/log_rotator.ts

@@ -50,6 +50,7 @@ export class LogRotator {
   public usePolling: boolean;
   public pollingInterval: number;
   private stalkerUsePollingPolicyTestTimeout: NodeJS.Timeout | null;
+  public shouldUsePolling: boolean;
 
   constructor(config: KibanaConfig, server: Server) {
     this.config = config;
@@ -64,6 +65,7 @@ export class LogRotator {
     this.stalker = null;
     this.usePolling = config.get('logging.rotate.usePolling');
     this.pollingInterval = config.get('logging.rotate.pollingInterval');
+    this.shouldUsePolling = false;
     this.stalkerUsePollingPolicyTestTimeout = null;
   }
 
@@ -150,12 +152,20 @@ export class LogRotator {
   }
 
   async _startLogFileSizeMonitor() {
-    this.usePolling = await this._shouldUsePolling();
+    this.usePolling = this.config.get('logging.rotate.usePolling');
+    this.shouldUsePolling = await this._shouldUsePolling();
 
-    if (this.usePolling && this.usePolling !== this.config.get('logging.rotate.usePolling')) {
+    if (this.usePolling && !this.shouldUsePolling) {
       this.log(
         ['warning', 'logging:rotate'],
-        'The current environment does not support `fs.watch`. Falling back to polling using `fs.watchFile`'
+        'Looks like your current environment support a faster algorithm then polling. You can try to disable `usePolling`'
+      );
+    }
+
+    if (!this.usePolling && this.shouldUsePolling) {
+      this.log(
+        ['error', 'logging:rotate'],
+        'Looks like within your current environment you need to use polling in order to enable log rotator. Please enable `usePolling`'
       );
     }