feat: add copy/truncate support (#19)

README.md

@@ -18,6 +18,8 @@ The environment variable `CRON_ROTATE` is used to schedule the rotation of the f
 
 If any files are rotated then, optionally, `LOGROTATE_POSTROTATE_COMMAND` is called. It can be necessary to signal the application that the rotation occurred so it can open a new file.
 
+Files are normally just renamed. You can set `LOGROTATE_COPYTRUNCATE_SUFFIXES` to instead copy and then truncate the file. Some files, like redirected output, can't be renamed and then deleted.
+
 Rotated files are appended with the file's change date and the current UTC timestamp. See: https://nodejs.org/api/fs.html#stat-time-values
 
 ### Stage 2 - Compress log file

src/constants.ts

@@ -15,6 +15,8 @@ export const LOGROTATE_AGE_MAX = process.env.LOGROTATE_AGE_MAX
   : 0;
 
 export const LOGROTATE_SUFFIX = process.env.LOGROTATE_SUFFIX ?? 'log';
+export const LOGROTATE_COPYTRUNCATE_SUFFIXES =
+  process.env.LOGROTATE_COPYTRUNCATE_SUFFIXES?.split(',') ?? [];
 export const LOGROTATE_POSTROTATE_COMMAND =
   process.env.LOGROTATE_POSTROTATE_COMMAND ?? '';
 export const JANITOR_COPIES = Number.parseInt(

src/cron/rotate.ts

@@ -7,6 +7,7 @@ import {
   LOGROTATE_POSTROTATE_COMMAND,
   LOGROTATE_DIRECTORY,
   LOGROTATE_SUFFIX,
+  LOGROTATE_COPYTRUNCATE_SUFFIXES,
   LOGROTATE_FILESIZE_MIN,
   LOGROTATE_AGE_MAX,
 } from '../constants';
@@ -64,9 +65,16 @@ export async function rotateLogs(db: DatabaseService) {
 async function rotateLog(db: DatabaseService, file: string) {
   const oldPath = path.join(LOGROTATE_DIRECTORY, file);
   const newPath = path.join(LOGROTATE_DIRECTORY, newLogName(file));
+  const strategy = computeRotateStrategy(file);
 
-  console.log(`rotate: ${oldPath} -> ${newPath}`);
-  fs.renameSync(oldPath, newPath);
+  console.log(`rotate: [${strategy}] ${oldPath} -> ${newPath}`);
+
+  if (strategy === 'rename') {
+    fs.renameSync(oldPath, newPath);
+  } else if (strategy === 'copytruncate') {
+    fs.copyFileSync(oldPath, newPath);
+    fs.truncateSync(oldPath);
+  }
 
   // Add log to database
   await db.addLog(file, newPath);
@@ -85,3 +93,12 @@ function changeDate(filePath: string) {
   const { ctime } = fs.statSync(filePath);
   return ctime;
 }
+
+function computeRotateStrategy(file: string) {
+  for (const suffix of LOGROTATE_COPYTRUNCATE_SUFFIXES) {
+    if (file.endsWith(suffix)) {
+      return 'copytruncate';
+    }
+  }
+  return 'rename';
+}