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

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

@@ -31,6 +31,48 @@ describe('MongoLogManager', function () {
     sinon.restore();
   });
 
+  it('constructor throws with invalid prefixes', function () {
+    expect(() => {
+      new MongoLogManager({
+        directory,
+        retentionDays,
+        prefix: '%asdabs/',
+        onwarn,
+        onerror,
+      });
+    }).to.throw();
+
+    expect(() => {
+      new MongoLogManager({
+        directory,
+        retentionDays,
+        prefix: '$$$$',
+        onwarn,
+        onerror,
+      });
+    }).to.throw();
+
+    expect(() => {
+      new MongoLogManager({
+        directory,
+        retentionDays,
+        prefix: 'abc_',
+        onwarn,
+        onerror,
+      });
+    }).not.to.throw();
+
+    expect(() => {
+      new MongoLogManager({
+        directory,
+        retentionDays,
+        prefix: 'something',
+        onwarn,
+        onerror,
+      });
+    }).not.to.throw();
+  });
+
   it('allows creating and writing to log files', async function () {
     const manager = new MongoLogManager({
       directory,
@@ -61,6 +103,19 @@ 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({
@@ -178,7 +233,57 @@ describe('MongoLogManager', function () {
     expect(leftoverFiles).deep.equals([faultyFile, ...validFiles.slice(3)]);
   });
 
-  it('cleans up least recent log files when over a storage limit', async function () {
+  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,
       retentionDays,

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

@@ -19,6 +19,8 @@ interface MongoLogOptions {
   maxLogFileCount?: number;
   /** The maximal size of log files which are kept. */
   retentionGB?: number;
+  /** Prefix to use for the log files */
+  prefix?: string;
   /** A handler for errors related to a specific filesystem path. */
   onerror: (err: Error, path: string) => unknown | Promise<void>;
   /** A handler for warnings related to a specific filesystem path. */
@@ -34,6 +36,13 @@ export class MongoLogManager {
   _options: MongoLogOptions;
 
   constructor(options: MongoLogOptions) {
+    if (options.prefix) {
+      if (!/^[a-z0-9_]+$/i.test(options.prefix)) {
+        throw new Error(
+          'Prefix must only contain letters, numbers, and underscores'
+        );
+      }
+    }
     this._options = options;
   }
 
@@ -48,6 +57,10 @@ export class MongoLogManager {
     }
   }
 
+  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;
@@ -80,8 +93,11 @@ 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();
@@ -143,7 +159,7 @@ 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;