Add debug logging for metrics collection failures

CHANGELOG.md

@@ -41,6 +41,7 @@ This release marks our first release under the Prometheus umbrella.
 
 ### Added
 
+- Add debug logging for metrics collection failures.
 - Node 26 added to the test matrix
 - Expanded benchmarking code
 - new WorkerRegistry to provide equivalent support to AggregatorRegistry

benchmarks/index.js

@@ -14,8 +14,9 @@
 
 'use strict';
 
+const { debuglog } = require('node:util');
+const debug = debuglog('prom:benchmark');
 const Benchmark = require('faceoff').default;
-const debug = require('debug')('benchmark');
 
 /**
  * Async suite workaround. benchmark-regression forwards no options to

lib/metrics/eventLoopLag.js

@@ -14,14 +14,17 @@
 
 'use strict';
 
+const { debuglog } = require('node:util');
 const Gauge = require('../gauge');
 
+const debug = debuglog('prom:metrics:event-loop-lag');
+
 // Check if perf_hooks module is available
 let perf_hooks;
 try {
 	perf_hooks = require('perf_hooks');
-} catch {
-	// node version is too old
+} catch (error) {
+	debug('perf_hooks module is unavailable: %o', error);
 }
 
 // Reported always.

lib/metrics/gc.js

@@ -13,14 +13,17 @@
 // limitations under the License.
 
 'use strict';
+const { debuglog } = require('node:util');
 const Histogram = require('../histogram');
 
+const debug = debuglog('prom:metrics:gc');
+
 let perf_hooks;
 
 try {
 	perf_hooks = require('perf_hooks');
-} catch {
-	// node version is too old
+} catch (error) {
+	debug('perf_hooks module is unavailable: %o', error);
 }
 
 const NODEJS_GC_DURATION_SECONDS = 'nodejs_gc_duration_seconds';

lib/metrics/helpers/safeMemoryUsage.js

@@ -14,11 +14,16 @@
 
 'use strict';
 
+const { debuglog } = require('node:util');
+
+const debug = debuglog('prom:metrics:safe-memory-usage');
+
 // process.memoryUsage() can throw on some platforms, see #67
 function safeMemoryUsage() {
 	try {
 		return process.memoryUsage();
-	} catch {
+	} catch (error) {
+		debug('process.memoryUsage() failed: %o', error);
 		return;
 	}
 }

lib/metrics/helpers/safeRss.js

@@ -14,11 +14,16 @@
 
 'use strict';
 
+const { debuglog } = require('node:util');
+
+const debug = debuglog('prom:metrics:safe-rss');
+
 // process.memoryUsage.rss() can throw on some platforms, see #67
 function safeRss() {
 	try {
 		return process.memoryUsage.rss();
-	} catch {
+	} catch (error) {
+		debug('process.memoryUsage.rss() failed: %o', error);
 		return;
 	}
 }

lib/metrics/osMemoryHeapLinux.js

@@ -14,9 +14,12 @@
 
 'use strict';
 
+const { debuglog } = require('node:util');
 const Gauge = require('../gauge');
 const fs = require('fs');
 
+const debug = debuglog('prom:metrics:os-memory-heap-linux');
+
 const values = ['VmSize', 'VmRSS', 'VmData'];
 
 const PROCESS_RESIDENT_MEMORY = 'process_resident_memory_bytes';
@@ -70,8 +73,8 @@ module.exports = (registry, config = {}) => {
 				residentMemGauge.set(labels, structuredOutput.VmRSS);
 				virtualMemGauge.set(labels, structuredOutput.VmSize);
 				heapSizeMemGauge.set(labels, structuredOutput.VmData);
-			} catch {
-				// noop
+			} catch (error) {
+				debug('failed to collect Linux memory metrics: %o', error);
 			}
 		},
 	});

lib/metrics/processMaxFileDescriptors.js

@@ -14,9 +14,12 @@
 
 'use strict';
 
+const { debuglog } = require('node:util');
 const Gauge = require('../gauge');
 const fs = require('fs');
 
+const debug = debuglog('prom:metrics:process-max-fds');
+
 const PROCESS_MAX_FDS = 'process_max_fds';
 
 let maxFds;
@@ -34,7 +37,8 @@ module.exports = (registry, config = {}) => {
 					break;
 				}
 			}
-		} catch {
+		} catch (error) {
+			debug('failed to collect maximum file descriptors: %o', error);
 			return;
 		}
 	}

lib/metrics/processOpenFileDescriptors.js

@@ -14,10 +14,13 @@
 
 'use strict';
 
+const { debuglog } = require('node:util');
 const Gauge = require('../gauge');
 const fs = require('fs');
 const process = require('process');
 
+const debug = debuglog('prom:metrics:process-open-fds');
+
 const PROCESS_OPEN_FDS = 'process_open_fds';
 
 module.exports = (registry, config = {}) => {
@@ -40,8 +43,8 @@ module.exports = (registry, config = {}) => {
 				// Minus 1 to not count the fd that was used by readdirSync(),
 				// it's now closed.
 				this.set(labels, fds.length - 1);
-			} catch {
-				// noop
+			} catch (error) {
+				debug('failed to collect open file descriptors: %o', error);
 			}
 		},
 	});

package.json

@@ -35,7 +35,6 @@
 	"homepage": "https://github.com/prometheus/client_js",
 	"devDependencies": {
 		"@eslint/js": "^9.29.0",
-		"debug": "^4.4.1",
 		"eslint": "^9.29.0",
 		"eslint-config-prettier": "^10.1.5",
 		"eslint-plugin-jsdoc": "^61.4.1",