ScribeLogger moved to common

Summary: There's nothing specific nor private about the ScribeLogger, so it is moved to flipper-common.

Reviewed By: LukeDefeo

Differential Revision: D48556074

fbshipit-source-id: aa9446036fd07fe6e6debc5a978a42308fc93fe0

desktop/flipper-common/src/index.tsx

@@ -21,6 +21,7 @@ export {
   NoopLogger,
 } from './utils/Logger';
 export * from './utils/LoggerTailer';
+export * from './utils/ScribeLogger';
 export * from './server-types';
 export * from './companion-types';
 export * from './ServerAddOn';

desktop/flipper-common/src/utils/ScribeLogger.tsx

@@ -0,0 +1,94 @@
+/**
+ * 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
+ */
+
+const FLUSH_TIMEOUT = 500;
+const MAX_MESSAGES = 1000;
+
+export type ScribeMessage = {
+  category: string;
+  message: string;
+};
+
+/**
+ * Send messages to arbitrary Scribe categories. This is useful to log data to
+ * LogView, Scuba, Hive, etc.
+ */
+export class ScribeLogger {
+  constructor(
+    sender: (messages: Array<ScribeMessage>) => Promise<void>,
+    disabled = false,
+    flushTimeout = FLUSH_TIMEOUT,
+  ) {
+    this.isFlushPending = false;
+    this.queue = [];
+    this.sendMessages = sender;
+    this.flushTimeout = flushTimeout;
+    this.disabled = disabled;
+  }
+
+  isFlushPending: boolean;
+  queue: Array<ScribeMessage>;
+  sendMessages: (messages: Array<ScribeMessage>) => Promise<void>;
+  flushTimeout: number;
+  disabled: boolean;
+
+  /**
+   * Send all the queued messages and reset.
+   */
+  flushQueue = async () => {
+    const messages = this.queue.splice(0); // copy & clear
+    try {
+      // send all the message currently in the queue
+      await this.sendMessages(messages);
+    } catch (e) {
+      console.debug(`[ScribeLogger] Failed to send messages: ${e}`);
+      // restore messages if emit failed
+      this.queue = messages.concat(this.queue);
+      this.enforceQueueLimit();
+    } finally {
+      // reset the queue
+      this.isFlushPending = false;
+    }
+  };
+
+  /**
+   * Add a message to be queued. Start a queue flush timer if one isn't already pending.
+   */
+  queueSend(message: ScribeMessage) {
+    this.queue.push(message);
+    this.enforceQueueLimit();
+
+    // start a flush timer if none exists
+    if (this.isFlushPending === false) {
+      this.isFlushPending = true;
+      if (this.flushTimeout >= 0) {
+        setTimeout(this.flushQueue, FLUSH_TIMEOUT);
+      } else {
+        this.flushQueue();
+      }
+    }
+  }
+
+  enforceQueueLimit() {
+    if (this.queue.length > MAX_MESSAGES) {
+      console.debug('[ScribeLogger] Queue full, dropping oldest messages');
+      this.queue = this.queue.slice(Math.floor(MAX_MESSAGES / 10));
+    }
+  }
+
+  /**
+   * Messages are not guaranteed to be sent right away.
+   */
+  send(message: ScribeMessage) {
+    if (this.disabled) {
+      return;
+    }
+    this.queueSend(message);
+  }
+}