problem: no metrics enabled for file based log

src/main/kotlin/io/emeraldpay/dshackle/monitoring/BufferingLogWriter.kt

@@ -50,6 +50,10 @@ abstract class BufferingLogWriter<T>(
     }
     private val queue = QueuePublisher<T>(queueLimit, onError = onQueueError)
 
+    init {
+        metrics.queue = queue
+    }
+
     override fun submit(event: T) {
         metrics.produced()
         queue.offer(event)

src/main/kotlin/io/emeraldpay/dshackle/monitoring/CurrentLogWriter.kt

@@ -41,24 +41,21 @@ abstract class CurrentLogWriter<T>(
             }
 
             is LogTargetConfig.File -> {
+                val metrics = createMetrics()
                 val file = Path.of(targetConfig.filename)
                 log.info("Writing $category to $file")
                 requireNotNull(fileOptions)
                 logWriter = FileLogWriter<T>(
                     file, serializer,
                     startSleep = fileOptions.startSleep, flushSleep = fileOptions.flushSleep,
-                    batchLimit = fileOptions.batchLimit
+                    batchLimit = fileOptions.batchLimit,
+                    metrics = metrics
                 )
                 logWriter.start()
             }
 
             is LogTargetConfig.Socket -> {
-                val metrics = if (Global.metricsExtended) {
-                    LogMetrics.Enabled(category.name.lowercase(Locale.getDefault()))
-                } else {
-                    LogMetrics.None()
-                }
-
+                val metrics = createMetrics()
                 log.info("Sending $category to ${targetConfig.host}:${targetConfig.port}")
                 val encoding = when (targetConfig.encoding) {
                     LogTargetConfig.Encoding.NEW_LINE -> LogEncodingNewLine()
@@ -75,6 +72,12 @@ abstract class CurrentLogWriter<T>(
         }
     }
 
+    private fun createMetrics() = if (Global.metricsExtended) {
+        LogMetrics.Enabled(category.name.lowercase(Locale.getDefault()))
+    } else {
+        LogMetrics.None()
+    }
+
     data class FileOptions(
         val startSleep: Duration,
         val flushSleep: Duration,

src/main/kotlin/io/emeraldpay/dshackle/monitoring/FileLogWriter.kt

@@ -30,8 +30,9 @@ class FileLogWriter<T>(
     serializer: (T) -> ByteArray?,
     private val startSleep: Duration,
     private val flushSleep: Duration,
-    private val batchLimit: Int = 5000
-) : LogWriter<T>, BufferingLogWriter<T>(serializer, LogEncodingNewLine(), queueLimit = batchLimit) {
+    private val batchLimit: Int = 5000,
+    metrics: LogMetrics = LogMetrics.None(),
+) : LogWriter<T>, BufferingLogWriter<T>(serializer, LogEncodingNewLine(), queueLimit = batchLimit, metrics = metrics) {
 
     companion object {
         private val log = LoggerFactory.getLogger(FileLogWriter::class.java)

src/main/kotlin/io/emeraldpay/dshackle/monitoring/LogMetrics.kt

@@ -15,29 +15,42 @@
  */
 package io.emeraldpay.dshackle.monitoring
 
+import io.emeraldpay.dshackle.commons.QueuePublisher
 import io.micrometer.core.instrument.Counter
+import io.micrometer.core.instrument.Gauge
 import io.micrometer.core.instrument.Metrics
 
 interface LogMetrics {
 
+    var queue: QueuePublisher<*>?
+
     fun produced()
     fun collected()
     fun dropped()
 
     class Enabled(category: String) : LogMetrics {
-        private val produced = Counter.builder("monitoring_logs_produce")
+        override var queue: QueuePublisher<*>? = null
+
+        private val produced = Counter.builder("monitoringLogs_produce")
             .description("Log events produced by Dshackle")
             .tag("type", category)
             .register(Metrics.globalRegistry)
-        private val collected = Counter.builder("monitoring_logs_collect")
+        private val collected = Counter.builder("monitoringLogs_collect")
             .description("Log events successfully sent to a storage")
             .tag("type", category)
             .register(Metrics.globalRegistry)
-        private val dropped = Counter.builder("monitoring_logs_drop")
+        private val dropped = Counter.builder("monitoringLogs_drop")
             .description("Log events dropped w/o sending")
             .tag("type", category)
             .register(Metrics.globalRegistry)
 
+        init {
+            Gauge.builder("monitoringLogs_queueSize") { queue?.size?.toDouble() ?: 0.0 }
+                .description("Log events queue size")
+                .tag("type", category)
+                .register(Metrics.globalRegistry)
+        }
+
         override fun produced() {
             produced.increment()
         }
@@ -53,6 +66,8 @@ interface LogMetrics {
 
     class None : LogMetrics {
 
+        override var queue: QueuePublisher<*>? = null
+
         override fun produced() {
         }