From fd3fdd0e33383a704a00aec5044f7e4db6433e46 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Mon, 18 Sep 2023 11:12:22 +0200
Subject: [PATCH] backend-common: lazy root logger initialization

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
---
 .changeset/friendly-teachers-attend.md        |  5 ++
 .../src/logging/createRootLogger.ts           | 57 ++++++++++++++++---
 .../src/logging/globalLoggers.ts              |  4 ++
 3 files changed, 58 insertions(+), 8 deletions(-)
 create mode 100644 .changeset/friendly-teachers-attend.md

diff --git a/.changeset/friendly-teachers-attend.md b/.changeset/friendly-teachers-attend.md
new file mode 100644
index 0000000000..6d5c3cf745
--- /dev/null
+++ b/.changeset/friendly-teachers-attend.md
@@ -0,0 +1,5 @@
+---
+'@backstage/backend-common': patch
+---
+
+The root logger is now initialized lazily, fixing a circular dependency issue with `@backstage/backend-app-api` that would result in `Cannot read properties of undefined (reading 'redacter')`.
diff --git a/packages/backend-common/src/logging/createRootLogger.ts b/packages/backend-common/src/logging/createRootLogger.ts
index 2e6fe20525..f9a3ed4ba0 100644
--- a/packages/backend-common/src/logging/createRootLogger.ts
+++ b/packages/backend-common/src/logging/createRootLogger.ts
@@ -17,12 +17,26 @@
 import { WinstonLogger } from '@backstage/backend-app-api';
 import { merge } from 'lodash';
 import * as winston from 'winston';
-import { LoggerOptions } from 'winston';
+import { format, LoggerOptions } from 'winston';
 import { setRootLogger } from './globalLoggers';
+import { TransformableInfo } from 'logform';
 
-const redacter = WinstonLogger.redacter();
+const getRedacter = (() => {
+  let redacter: ReturnType<typeof WinstonLogger.redacter> | undefined =
+    undefined;
+  return () => {
+    if (!redacter) {
+      redacter = WinstonLogger.redacter();
+    }
+    return redacter;
+  };
+})();
 
-export const setRootLoggerRedactionList = redacter.add;
+export const setRootLoggerRedactionList = (
+  redactions: Iterable<string>,
+): void => {
+  getRedacter().add(redactions);
+};
 
 /**
  * A winston formatting function that finds occurrences of filteredKeys
@@ -33,15 +47,44 @@ export const setRootLoggerRedactionList = redacter.add;
 export function redactWinstonLogLine(
   info: winston.Logform.TransformableInfo,
 ): winston.Logform.TransformableInfo {
-  return redacter.format.transform(info) as winston.Logform.TransformableInfo;
+  return getRedacter().format.transform(
+    info,
+  ) as winston.Logform.TransformableInfo;
 }
 
+const colorizer = format.colorize();
+
+// NOTE: This is a copy of the WinstonLogger.colorFormat to avoid a circular dependency
 /**
  * Creates a pretty printed winston log formatter.
  *
  * @public
  */
-export const coloredFormat = WinstonLogger.colorFormat();
+export const coloredFormat = format.combine(
+  format.timestamp(),
+  format.colorize({
+    colors: {
+      timestamp: 'dim',
+      prefix: 'blue',
+      field: 'cyan',
+      debug: 'grey',
+    },
+  }),
+  format.printf((info: TransformableInfo) => {
+    const { timestamp, level, message, plugin, service, ...fields } = info;
+    const prefix = plugin || service;
+    const timestampColor = colorizer.colorize('timestamp', timestamp);
+    const prefixColor = colorizer.colorize('prefix', prefix);
+
+    const extraFields = Object.entries(fields)
+      .map(
+        ([key, value]) => `${colorizer.colorize('field', `${key}`)}=${value}`,
+      )
+      .join(' ');
+
+    return `${timestampColor} ${prefixColor} ${level} ${message} ${extraFields}`;
+  }),
+);
 
 /**
  * Creates a default "root" logger. This also calls {@link setRootLogger} under
@@ -64,7 +107,7 @@ export function createRootLogger(
         {
           level: env.LOG_LEVEL || 'info',
           format: winston.format.combine(
-            redacter.format,
+            getRedacter().format,
             env.NODE_ENV === 'production'
               ? winston.format.json()
               : WinstonLogger.colorFormat(),
@@ -84,5 +127,3 @@ export function createRootLogger(
 
   return logger;
 }
-
-setRootLogger(createRootLogger());
diff --git a/packages/backend-common/src/logging/globalLoggers.ts b/packages/backend-common/src/logging/globalLoggers.ts
index 7567deb646..8b473db211 100644
--- a/packages/backend-common/src/logging/globalLoggers.ts
+++ b/packages/backend-common/src/logging/globalLoggers.ts
@@ -15,6 +15,7 @@
  */
 
 import * as winston from 'winston';
+import { createRootLogger } from './createRootLogger';
 
 /**
  * A logger that just throws away all messages.
@@ -35,6 +36,9 @@ let rootLogger: winston.Logger;
  * @public
  */
 export function getRootLogger(): winston.Logger {
+  if (!rootLogger) {
+    rootLogger = createRootLogger();
+  }
   return rootLogger;
 }