feat(logger): Enable log buffering feature

This commit enables the buffering feature for the logger utility
It allows the user to configure the buffering functionality in the
logger constructor.

Author: ConnorKirk

Diff for: packages/logger/src/Logger.ts

@@ -172,25 +172,28 @@ class Logger extends Utility implements LoggerInterface {
   /**
    * Represents whether the buffering functionality is enabled in the logger
    */
-  protected isBufferEnabled = false;
+  protected isBufferEnabled = true;
 
+  /**
+   * Whether the buffer should be flushed when an error is logged
+   */
+  protected flushOnErrorLog = true;
   /**
    * Log level threshold for the buffer
    * Logs with a level lower than this threshold will be buffered
+   * Default is DEBUG
    */
-  protected bufferLogThreshold: number = LogLevelThreshold.DEBUG;
+  protected bufferAtVerbosity: number = LogLevelThreshold.DEBUG;
   /**
    * Max size of the buffer. Additions to the buffer beyond this size will
    * cause older logs to be evicted from the buffer
    */
-  readonly #maxBufferBytesSize = 1024;
+  #maxBufferBytesSize = 1024;
 
   /**
    * Contains buffered logs, grouped by _X_AMZN_TRACE_ID, each group with a max size of `maxBufferBytesSize`
    */
-  readonly #buffer: CircularMap<string> = new CircularMap({
-    maxBytesSize: this.#maxBufferBytesSize,
-  });
+  #buffer?: CircularMap<string>;
 
   /**
    * Log level used by the current instance of Logger.
@@ -330,6 +333,9 @@ class Logger extends Utility implements LoggerInterface {
    * @param extraInput - The extra input to log.
    */
   public error(input: LogItemMessage, ...extraInput: LogItemExtraInput): void {
+    if (this.isBufferEnabled && this.flushOnErrorLog) {
+      this.flushBuffer();
+    }
     this.processLogItem(LogLevelThreshold.ERROR, input, extraInput);
   }
 
@@ -1168,6 +1174,7 @@ class Logger extends Utility implements LoggerInterface {
       environment,
       jsonReplacerFn,
       logRecordOrder,
+      logBufferOptions,
     } = options;
 
     if (persistentLogAttributes && persistentKeys) {
@@ -1194,6 +1201,10 @@ class Logger extends Utility implements LoggerInterface {
     this.setLogIndentation();
     this.#jsonReplacerFn = jsonReplacerFn;
 
+    if (logBufferOptions !== undefined) {
+      this.#setLogBuffering(logBufferOptions);
+    }
+
     return this;
   }
 
@@ -1224,6 +1235,30 @@ class Logger extends Utility implements LoggerInterface {
     persistentKeys && this.appendPersistentKeys(persistentKeys);
   }
 
+  #setLogBuffering(
+    options: NonNullable<ConstructorOptions['logBufferOptions']>
+  ) {
+    if (options.maxBytes !== undefined) {
+      this.#maxBufferBytesSize = options.maxBytes;
+    }
+
+    this.#buffer = new CircularMap({
+      maxBytesSize: this.#maxBufferBytesSize,
+    });
+
+    if (options.enabled !== undefined) {
+      this.isBufferEnabled = options.enabled;
+    }
+
+    const bufferAtLogLevel = options.bufferAtVerbosity?.toUpperCase();
+
+    if (this.isValidLogLevel(bufferAtLogLevel)) {
+      this.bufferAtVerbosity = LogLevelThreshold[bufferAtLogLevel];
+
+      return;
+    }
+  }
+
   /**
    * Add a log to the buffer
    * @param xrayTraceId - _X_AMZN_TRACE_ID of the request
@@ -1243,20 +1278,20 @@ class Logger extends Utility implements LoggerInterface {
       this.logIndentation
     );
 
-    this.#buffer.setItem(xrayTraceId, stringified, logLevel);
+    this.#buffer?.setItem(xrayTraceId, stringified, logLevel);
   }
 
   /**
    * Flushes all items of the respective _X_AMZN_TRACE_ID within
    * the buffer.
    */
-  protected flushBuffer(): void {
+  flushBuffer(): void {
     const traceId = this.envVarsService.getXrayTraceId();
     if (traceId === undefined) {
       return;
     }
 
-    const buffer = this.#buffer.get(traceId);
+    const buffer = this.#buffer?.get(traceId);
     if (buffer === undefined) {
       return;
     }
@@ -1281,7 +1316,7 @@ class Logger extends Utility implements LoggerInterface {
       );
     }
 
-    this.#buffer.delete(traceId);
+    this.#buffer?.delete(traceId);
   }
   /**
    * Tests if the log meets the criteria to be buffered
@@ -1295,7 +1330,7 @@ class Logger extends Utility implements LoggerInterface {
     return (
       this.isBufferEnabled &&
       traceId !== undefined &&
-      logLevel <= this.bufferLogThreshold
+      logLevel <= this.bufferAtVerbosity
     );
   }
 }

Diff for: packages/logger/src/types/Logger.ts

@@ -173,12 +173,44 @@ type LogRecordOrderOption = {
   logFormatter?: never;
 };
 
+/**
+ * Options for the `logBuffer` constructor option.
+ *
+ * Used to configure the log buffer functionality.
+ */
+type LogBufferOption = {
+  logBufferOptions?: {
+    /**
+     * Whether logs should be buffered
+     */
+    enabled?: boolean;
+
+    /**
+     * Maximum size in bytes of each buffer.
+     */
+    maxBytes?: number;
+    /**
+     * Flush the buffer when an error is logged
+     */
+    flushOnErrorLog?: boolean;
+    /**
+     * The threshold to buffer logs. Logs with a level below
+     * this threshold will be buffered
+     */
+    bufferAtVerbosity?: Omit<
+      LogLevel,
+      'ERROR' | 'error' | 'CRITICAL' | 'critical' | 'SILENT' | 'silent'
+    >;
+  };
+};
+
 /**
  * Options to configure the Logger.
  */
 type ConstructorOptions = BaseConstructorOptions &
   (PersistentKeysOption | DeprecatedPersistentKeysOption) &
-  (LogFormatterOption | LogRecordOrderOption);
+  (LogFormatterOption | LogRecordOrderOption) &
+  LogBufferOption;
 
 type LogItemMessage = string | LogAttributesWithMessage;
 type LogItemExtraInput = [Error | string] | LogAttributes[];
@@ -194,6 +226,7 @@ type LoggerInterface = {
   critical(input: LogItemMessage, ...extraInput: LogItemExtraInput): void;
   debug(input: LogItemMessage, ...extraInput: LogItemExtraInput): void;
   error(input: LogItemMessage, ...extraInput: LogItemExtraInput): void;
+  flushBuffer(): void;
   getLevelName(): Uppercase<LogLevel>;
   getLogEvent(): boolean;
   getPersistentLogAttributes(): LogAttributes;