feat(mongodb-log-writer): add ability to specify a prefix for log files

This is needed for mongosh to use a `mongosh_` prefix for custom log directories.

Author: gagik

packages/mongodb-log-writer/src/mongo-log-manager.spec.ts

@@ -59,6 +59,19 @@ describe('MongoLogManager', function () {
     expect(log[0].t.$date).to.be.a('string');
   });
 
+  it('can take a custom prefix for log files', async function () {
+    const manager = new MongoLogManager({
+      directory,
+      retentionDays,
+      prefix: 'custom_',
+      onwarn,
+      onerror,
+    });
+
+    const writer = await manager.createLogWriter();
+    expect(writer.logFilePath as string).to.match(/custom_/);
+  });
+
   it('cleans up old log files when requested', async function () {
     retentionDays = 0.000001; // 86.4 ms
     const manager = new MongoLogManager({
@@ -124,6 +137,56 @@ describe('MongoLogManager', function () {
     expect(await getFilesState(paths)).to.equal('0000011111');
   });
 
+  it('cleanup only applies to files with the prefix, if set', async function () {
+    const manager = new MongoLogManager({
+      directory,
+      retentionDays,
+      maxLogFileCount: 7,
+      prefix: 'custom_',
+      onwarn,
+      onerror,
+    });
+
+    const paths: string[] = [];
+    const offset = Math.floor(Date.now() / 1000);
+
+    // Create 4 files: 2 with a different prefix and 2 with no prefix
+    for (let i = 1; i >= 0; i--) {
+      const withoutPrefix = path.join(
+        directory,
+        ObjectId.createFromTime(offset - i).toHexString() + '_log'
+      );
+      await fs.writeFile(withoutPrefix, '');
+      paths.push(withoutPrefix);
+
+      const withDifferentPrefix = path.join(
+        directory,
+        'different_' +
+          ObjectId.createFromTime(offset - i).toHexString() +
+          '_log'
+      );
+      await fs.writeFile(withDifferentPrefix, '');
+      paths.push(withDifferentPrefix);
+    }
+
+    // Create 10 files with the prefix
+    for (let i = 9; i >= 0; i--) {
+      const filename = path.join(
+        directory,
+        `custom_${ObjectId.createFromTime(offset - i).toHexString()}_log`
+      );
+      await fs.writeFile(filename, '');
+      paths.push(filename);
+    }
+
+    expect(await getFilesState(paths)).to.equal('11111111111111');
+    await manager.cleanupOldLogFiles();
+
+    // The first 4 files without the right prefix should still be there.
+    // The next (oldest) 3 files with the prefix should be deleted.
+    expect(await getFilesState(paths)).to.equal('11110001111111');
+  });
+
   it('cleans up least recent log files when requested with a storage limit', async function () {
     const manager = new MongoLogManager({
       directory,

packages/mongodb-log-writer/src/mongo-log-manager.ts

@@ -19,6 +19,8 @@ interface MongoLogOptions {
   maxLogFileCount?: number;
   /** The maximal GB of log files which are kept. */
   logRetentionGB?: number;
+  /** Prefix to use for the log files */
+  prefix?: string;
   /** A handler for warnings related to a specific filesystem path. */
   onerror: (err: Error, path: string) => unknown | Promise<void>;
   /** A handler for errors related to a specific filesystem path. */
@@ -37,6 +39,10 @@ export class MongoLogManager {
     this._options = options;
   }
 
+  private get prefix() {
+    return this._options.prefix ?? '';
+  }
+
   /** Clean up log files older than `retentionDays`. */
   async cleanupOldLogFiles(maxDurationMs = 5_000): Promise<void> {
     const dir = this._options.directory;
@@ -73,8 +79,11 @@ export class MongoLogManager {
       if (Date.now() - deletionStartTimestamp > maxDurationMs) break;
 
       if (!dirent.isFile()) continue;
-      const { id } =
-        /^(?<id>[a-f0-9]{24})_log(\.gz)?$/i.exec(dirent.name)?.groups ?? {};
+      const logRegExp = new RegExp(
+        `^${this.prefix}(?<id>[a-f0-9]{24})_log(\\.gz)?$`,
+        'i'
+      );
+      const { id } = logRegExp.exec(dirent.name)?.groups ?? {};
       if (!id) continue;
       const fileTimestamp = +new ObjectId(id).getTimestamp();
       const fullPath = path.join(dir, dirent.name);
@@ -141,7 +150,7 @@ export class MongoLogManager {
     const doGzip = !!this._options.gzip;
     const logFilePath = path.join(
       this._options.directory,
-      `${logId}_log${doGzip ? '.gz' : ''}`
+      `${this.prefix}${logId}_log${doGzip ? '.gz' : ''}`
     );
 
     let originalTarget: Writable;