add OTLP logging appender factory

service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java

@@ -385,6 +385,7 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
     dynamicConfigurationManager.start();
 
     MetricsUtil.configureRegistries(config, environment, dynamicConfigurationManager);
+    MetricsUtil.configureLogging(config, environment);
 
     ExperimentEnrollmentManager experimentEnrollmentManager = new ExperimentEnrollmentManager(dynamicConfigurationManager);
 

service/src/main/java/org/whispersystems/textsecuregcm/metrics/MetricsUtil.java

@@ -8,6 +8,7 @@ package org.whispersystems.textsecuregcm.metrics;
 import com.codahale.metrics.SharedMetricRegistries;
 import com.google.common.annotations.VisibleForTesting;
 import io.dropwizard.core.setup.Environment;
+import io.dropwizard.lifecycle.Managed;
 import io.micrometer.core.instrument.Meter;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Metrics;
@@ -21,6 +22,14 @@ import io.micrometer.core.instrument.config.MeterFilter;
 import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 import io.micrometer.registry.otlp.OtlpMeterRegistry;
 import io.micrometer.statsd.StatsdMeterRegistry;
+import io.opentelemetry.exporter.otlp.http.logs.OtlpHttpLogRecordExporter;
+import io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender;
+import io.opentelemetry.sdk.OpenTelemetrySdk;
+import io.opentelemetry.sdk.logs.SdkLoggerProvider;
+import io.opentelemetry.sdk.logs.export.BatchLogRecordProcessor;
+import io.opentelemetry.sdk.resources.Resource;
+import io.opentelemetry.semconv.ServiceAttributes;
+
 import java.time.Duration;
 import org.whispersystems.textsecuregcm.WhisperServerConfiguration;
 import org.whispersystems.textsecuregcm.WhisperServerVersion;
@@ -99,6 +108,34 @@ public class MetricsUtil {
         new MicrometerRegistryManager(Metrics.globalRegistry, shutdownWaitDuration));
   }
 
+  public static void configureLogging(final WhisperServerConfiguration config, final Environment environment) {
+    if (!config.getOpenTelemetryConfiguration().enabled()) {
+      return;
+    }
+    final OpenTelemetrySdk openTelemetry =
+      OpenTelemetrySdk.builder()
+        .setLoggerProvider(
+          SdkLoggerProvider.builder()
+            .setResource(
+              Resource.builder()
+                .put(ServiceAttributes.SERVICE_NAME, "chat")
+                .put(ServiceAttributes.SERVICE_VERSION, WhisperServerVersion.getServerVersion())
+                .build())
+            .addLogRecordProcessor(
+              BatchLogRecordProcessor.builder(OtlpHttpLogRecordExporter.getDefault()).build())
+            .build())
+        .build();
+
+    OpenTelemetryAppender.install(openTelemetry);
+
+    environment.lifecycle().manage(new Managed() {
+      @Override
+      public void stop() {
+        openTelemetry.shutdown();
+      }
+    });
+  }
+
   @VisibleForTesting
   static void configureMeterFilters(MeterRegistry.Config config,
       final DynamicConfigurationManager<DynamicConfiguration> dynamicConfigurationManager) {

service/src/main/java/org/whispersystems/textsecuregcm/metrics/OpenTelemetryAppenderFactory.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.metrics;
+
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.Appender;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import io.dropwizard.logging.common.AbstractAppenderFactory;
+import io.dropwizard.logging.common.async.AsyncAppenderFactory;
+import io.dropwizard.logging.common.filter.LevelFilterFactory;
+import io.dropwizard.logging.common.layout.LayoutFactory;
+import io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender;
+import jakarta.validation.constraints.NotEmpty;
+
+@JsonTypeName("otlp")
+public class OpenTelemetryAppenderFactory extends AbstractAppenderFactory<ILoggingEvent> {
+
+  @JsonProperty
+  private String destination;
+
+  @Override
+  public Appender<ILoggingEvent> build(
+      final LoggerContext context,
+      final String applicationName,
+      final LayoutFactory<ILoggingEvent> layoutFactory,
+      final LevelFilterFactory<ILoggingEvent> levelFilterFactory,
+      final AsyncAppenderFactory<ILoggingEvent> asyncAppenderFactory) {
+
+    final OpenTelemetryAppender appender = new OpenTelemetryAppender();
+    appender.setCaptureCodeAttributes(true);
+    appender.setCaptureLoggerContext(true);
+
+    // The installation of an OpenTelemetry configuration happens in
+    // WhisperServerService (or CommandDependencies), in order to let us tie
+    // into Dropwizard's lifecycle management; this allows us to buffer any
+    // logs emitted between now and that happening.
+    appender.setNumLogsCapturedBeforeOtelInstall(1000);
+
+    appender.addFilter(levelFilterFactory.build(threshold));
+    getFilterFactories().forEach(f -> appender.addFilter(f.build()));
+    appender.start();
+
+    return wrapAsync(appender, asyncAppenderFactory);
+  }
+}

service/src/main/java/org/whispersystems/textsecuregcm/workers/CommandDependencies.java

@@ -45,6 +45,7 @@ import org.whispersystems.textsecuregcm.experiment.ExperimentEnrollmentManager;
 import org.whispersystems.textsecuregcm.experiment.PushNotificationExperimentSamples;
 import org.whispersystems.textsecuregcm.grpc.net.GrpcClientConnectionManager;
 import org.whispersystems.textsecuregcm.limits.RateLimiters;
+import org.whispersystems.textsecuregcm.metrics.MetricsUtil;
 import org.whispersystems.textsecuregcm.metrics.MicrometerAwsSdkMetricPublisher;
 import org.whispersystems.textsecuregcm.push.APNSender;
 import org.whispersystems.textsecuregcm.push.FcmSender;
@@ -127,6 +128,8 @@ record CommandDependencies(
       throws IOException, GeneralSecurityException, InvalidInputException {
     Clock clock = Clock.systemUTC();
 
+    MetricsUtil.configureLogging(configuration, environment);
+
     environment.getObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
 
     final AwsCredentialsProvider awsCredentialsProvider = configuration.getAwsCredentialsConfiguration().build();