Logging: Allowed other file formats to be passed through config

ref https://linear.app/ghost/issue/PRO-1533

- The filename is currently hardcoded which causes a large amount of randomness when the hostnames for configured Ghost instances change
- This allows us to hardcode the filename to a specific format (eg `production.log`) since uniqueness is already handled elsewhere (eg the folder name)

Author: jloh

packages/logging/README.md

@@ -36,4 +36,4 @@ Follow the instructions for the top-level repo.
 
 # Copyright & License 
 
-Copyright (c) 2013-2025 Ghost Foundation - Released under the [MIT license](LICENSE).
+Copyright (c) 2013-2025 Ghost Foundation - Released under the [MIT license](LICENSE).

packages/logging/lib/GhostLogger.js

@@ -26,6 +26,8 @@ class GhostLogger {
      * transports:      An array of comma separated transports (e.g. stdout, stderr, geld, loggly, file)
      * rotation:        Enable or disable file rotation.
      * path:            Path where to store log files.
+     * filename:        Optional filename template for log files. Supports {env} and {domain} placeholders.
+     *                  If not provided, defaults to {domain}_{env} format.
      * loggly:          Loggly transport configuration.
      * elasticsearch:   Elasticsearch transport configuration
      * gelf:            Gelf transport configuration.
@@ -45,6 +47,7 @@ class GhostLogger {
         this.logBody = options.logBody || false;
         this.mode = process.env.MODE || options.mode || 'short';
         this.path = options.path || process.cwd();
+        this.filename = options.filename || '{domain}_{env}';
         this.loggly = options.loggly || {};
         this.elasticsearch = options.elasticsearch || {};
         this.gelf = options.gelf || {};
@@ -275,6 +278,30 @@ class GhostLogger {
         };
     }
 
+    /**
+     * @description Sanitize domain for use in filenames.
+     * Replaces all non-word characters with underscores.
+     * @param {string} domain - The domain to sanitize
+     * @returns {string} Sanitized domain safe for filenames
+     * @example
+     * sanitizeDomain('http://my-domain.com') // returns 'http___my_domain_com'
+     */
+    sanitizeDomain(domain) {
+        return domain.replace(/[^\w]/gi, '_');
+    }
+
+    /**
+     * @description Replace placeholders in filename template.
+     * @param {string} template - Filename template with placeholders
+     * @returns {string} Filename with placeholders replaced
+     */
+    // TODO: Expand to other placeholders?
+    replaceFilenamePlaceholders(template) {
+        return template
+            .replace(/{env}/g, this.env)
+            .replace(/{domain}/g, this.sanitizeDomain(this.domain));
+    }
+
     /**
      * @description Setup file stream.
      *
@@ -283,8 +310,7 @@ class GhostLogger {
      * 2. file-all: everything
      */
     setFileStream() {
-        // e.g. http://my-domain.com --> http___my_domain_com
-        const sanitizedDomain = this.domain.replace(/[^\w]/gi, '_');
+        const baseFilename = this.replaceFilenamePlaceholders(this.filename);
 
         // CASE: target log folder does not exist, show warning
         if (!fs.existsSync(this.path)) {
@@ -296,7 +322,7 @@ class GhostLogger {
             if (this.rotation.useLibrary) {
                 const RotatingFileStream = require('@tryghost/bunyan-rotating-filestream');
                 const rotationConfig = {
-                    path: `${this.path}${sanitizedDomain}_${this.env}.log`,
+                    path: `${this.path}${baseFilename}.log`,
                     period: this.rotation.period,
                     threshold: this.rotation.threshold,
                     totalFiles: this.rotation.count,
@@ -310,7 +336,7 @@ class GhostLogger {
                         name: this.name,
                         streams: [{
                             stream: new RotatingFileStream(Object.assign({}, rotationConfig, {
-                                path: `${this.path}${sanitizedDomain}_${this.env}.error.log`
+                                path: `${this.path}${baseFilename}.error.log`
                             })),
                             level: 'error'
                         }],
@@ -337,7 +363,7 @@ class GhostLogger {
                         name: this.name,
                         streams: [{
                             type: 'rotating-file',
-                            path: `${this.path}${sanitizedDomain}_${this.env}.error.log`,
+                            path: `${this.path}${baseFilename}.error.log`,
                             period: this.rotation.period,
                             count: this.rotation.count,
                             level: 'error'
@@ -352,7 +378,7 @@ class GhostLogger {
                         name: this.name,
                         streams: [{
                             type: 'rotating-file',
-                            path: `${this.path}${sanitizedDomain}_${this.env}.log`,
+                            path: `${this.path}${baseFilename}.log`,
                             period: this.rotation.period,
                             count: this.rotation.count,
                             level: this.level
@@ -367,7 +393,7 @@ class GhostLogger {
                 log: bunyan.createLogger({
                     name: this.name,
                     streams: [{
-                        path: `${this.path}${sanitizedDomain}_${this.env}.error.log`,
+                        path: `${this.path}${baseFilename}.error.log`,
                         level: 'error'
                     }],
                     serializers: this.serializers
@@ -379,7 +405,7 @@ class GhostLogger {
                 log: bunyan.createLogger({
                     name: this.name,
                     streams: [{
-                        path: `${this.path}${sanitizedDomain}_${this.env}.log`,
+                        path: `${this.path}${baseFilename}.log`,
                         level: this.level
                     }],
                     serializers: this.serializers

packages/logging/test/logging.test.js

@@ -457,6 +457,92 @@ describe('Logging', function () {
         });
     });
 
+    describe('filename computation', function () {
+        it('sanitizeDomain should replace non-word characters with underscores', function () {
+            var ghostLogger = new GhostLogger();
+            ghostLogger.sanitizeDomain('http://my-domain.com').should.eql('http___my_domain_com');
+            ghostLogger.sanitizeDomain('localhost').should.eql('localhost');
+            ghostLogger.sanitizeDomain('example.com:8080').should.eql('example_com_8080');
+        });
+
+        it('replaceFilenamePlaceholders should replace {env} placeholder', function () {
+            var ghostLogger = new GhostLogger({env: 'production'});
+            ghostLogger.replaceFilenamePlaceholders('{env}').should.eql('production');
+        });
+
+        it('replaceFilenamePlaceholders should replace {domain} placeholder', function () {
+            var ghostLogger = new GhostLogger({domain: 'http://example.com'});
+            ghostLogger.replaceFilenamePlaceholders('{domain}').should.eql('http___example_com');
+        });
+
+        it('replaceFilenamePlaceholders should replace both {env} and {domain} placeholders', function () {
+            var ghostLogger = new GhostLogger({
+                domain: 'http://example.com',
+                env: 'staging'
+            });
+            ghostLogger.replaceFilenamePlaceholders('{domain}-{env}').should.eql('http___example_com-staging');
+            ghostLogger.replaceFilenamePlaceholders('{env}.{domain}').should.eql('staging.http___example_com');
+        });
+
+        it('logger should return default format when no filename option provided', function () {
+            var ghostLogger = new GhostLogger({
+                domain: 'http://example.com',
+                env: 'production'
+            });
+            ghostLogger.filename.should.eql('{domain}_{env}');
+        });
+
+        it('logger should use filename template when provided', function () {
+            var ghostLogger = new GhostLogger({
+                domain: 'http://example.com',
+                env: 'production',
+                filename: '{env}'
+            });
+            ghostLogger.filename.should.eql('{env}');
+        });
+
+        it('file stream should use custom filename template', function () {
+            const tempDir = './test-logs/';
+            const rimraf = function (dir) {
+                if (fs.existsSync(dir)) {
+                    fs.readdirSync(dir).forEach(function (file) {
+                        const curPath = dir + '/' + file;
+                        if (fs.lstatSync(curPath).isDirectory()) {
+                            rimraf(curPath);
+                        } else {
+                            fs.unlinkSync(curPath);
+                        }
+                    });
+                    fs.rmdirSync(dir);
+                }
+            };
+
+            // Create temp directory
+            if (!fs.existsSync(tempDir)) {
+                fs.mkdirSync(tempDir, {recursive: true});
+            }
+
+            var ghostLogger = new GhostLogger({
+                domain: 'test.com',
+                env: 'production',
+                filename: '{env}',
+                transports: ['file'],
+                path: tempDir
+            });
+
+            ghostLogger.info('Test log message');
+
+            // Give it a moment to write
+            setTimeout(function () {
+                fs.existsSync(tempDir + 'production.log').should.eql(true);
+                fs.existsSync(tempDir + 'production.error.log').should.eql(true);
+
+                // Cleanup
+                rimraf(tempDir);
+            }, 100);
+        });
+    });
+
     describe('serialization', function () {
         it('serializes error into correct object', function (done) {
             const err = new errors.NotFoundError();