Remove Tail

Summary: We no longer need to Tail the logs as we stream the logs over WebSockets (see D37459924 (dcbc7c40bb))

Reviewed By: lblasa

Differential Revision: D37550482

fbshipit-source-id: 92a87f2ba1ecec140bbbb9e71df107341765ad46

desktop/flipper-server-core/src/index.tsx

@@ -12,7 +12,6 @@ export {loadSettings} from './utils/settings';
 export {loadLauncherSettings} from './utils/launcherSettings';
 export {loadProcessConfig} from './utils/processConfig';
 export {getEnvironmentInfo} from './utils/environmentInfo';
-export * from './utils/tail';
 export {getGatekeepers} from './gk';
 export {setupPrefetcher} from './fb-stubs/Prefetcher';
 export * from './server/attachSocketServer';

desktop/flipper-server-core/src/utils/tail.tsx

@@ -1,144 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @format
- */
-
-import EventEmitter from 'events';
-import fs, {FSWatcher} from 'fs-extra';
-import path from 'path';
-
-export type TailOptions = {
-  separator: RegExp;
-  encoding: BufferEncoding;
-  fromBeginning: boolean;
-};
-
-type TailBlock = {
-  start: number;
-  end: number;
-};
-
-export class Tail extends EventEmitter {
-  absPath: string;
-  dispatcher = new EventEmitter();
-  buffer = '';
-  queue: TailBlock[] = [];
-  isWatching = false;
-  currentCursorPosition = 0;
-  watcher: FSWatcher | undefined = undefined;
-
-  constructor(
-    private readonly filename: string,
-    private readonly options: TailOptions = {
-      separator: /[\r]{0,1}\n/,
-      fromBeginning: true,
-      encoding: 'utf8',
-    },
-  ) {
-    super();
-
-    this.absPath = path.dirname(this.filename);
-    this.dispatcher.on('next', () => {
-      this.read_();
-    });
-  }
-
-  async watch() {
-    if (this.isWatching) {
-      return;
-    }
-    this.isWatching = true;
-
-    let startingCursor = 0;
-    if (!this.options.fromBeginning) {
-      startingCursor = await this.latestPosition_();
-    }
-
-    this.watch_(startingCursor, this.options.fromBeginning);
-  }
-
-  unwatch() {
-    if (this.watcher) {
-      this.watcher.close();
-    }
-    this.isWatching = false;
-  }
-
-  private async latestPosition_(): Promise<number> {
-    return (await fs.stat(this.filename)).size;
-  }
-
-  private read_() {
-    if (this.queue.length >= 1) {
-      const block = this.queue[0];
-      if (block.end > block.start) {
-        const stream = fs.createReadStream(this.filename, {
-          start: block.start,
-          end: block.end - 1,
-          encoding: this.options.encoding,
-        });
-        stream.on('error', (error) => {
-          this.emit('error', error);
-        });
-        stream.on('end', () => {
-          this.queue.shift();
-          if (this.queue.length > 0) {
-            this.dispatcher.emit('next');
-          }
-          if (this.buffer.length > 0) {
-            this.emit('line', this.buffer);
-            this.buffer = '';
-          }
-        });
-        stream.on('data', (d) => {
-          this.buffer += d;
-          const parts = this.buffer.split(this.options.separator);
-          // The last part may be an incomplete chunk, so
-          // push that back into the buffer. Otherwise, reset buffer.
-          this.buffer = parts.pop() || '';
-          for (const chunk of parts) {
-            this.emit('line', chunk);
-          }
-        });
-      }
-    }
-  }
-
-  private async fileUpdated_() {
-    const latestPosition = await this.latestPosition_();
-    // Case where text is not appended but it's actually a w+
-    if (latestPosition < this.currentCursorPosition) {
-      this.currentCursorPosition = latestPosition;
-    } else if (latestPosition > this.currentCursorPosition) {
-      this.queue.push({start: this.currentCursorPosition, end: latestPosition});
-      this.currentCursorPosition = latestPosition;
-      // Only emit if the queue was empty and now is not.
-      if (this.queue.length == 1) {
-        this.dispatcher.emit('next');
-      }
-    }
-  }
-
-  private watch_(cursor: number, readPrevious: boolean) {
-    this.currentCursorPosition = cursor;
-    if (readPrevious) {
-      this.fileUpdated_();
-    }
-
-    this.watcher = fs.watch(this.filename, {}, (eventType, filename) => {
-      this.watchEvent_(eventType, filename);
-    });
-  }
-
-  private watchEvent_(eventType: string, _filename: string) {
-    try {
-      if (eventType === 'change') {
-        this.fileUpdated_();
-      }
-    } catch (err) {}
-  }
-}