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Author: Cecile Terpin

dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java

@@ -69,6 +69,7 @@ public final class ConfigDefaults {
   static final boolean DEFAULT_DB_CLIENT_HOST_SPLIT_BY_INSTANCE_TYPE_SUFFIX = false;
   static final boolean DEFAULT_DB_CLIENT_HOST_SPLIT_BY_HOST = false;
   static final String DEFAULT_DB_DBM_PROPAGATION_MODE_MODE = "disabled";
+  // Default value is set to -1, it disables the latency trace interceptor
   static final int DEFAULT_TRACE_LATENCY_INTERCEPTOR_VALUE = -1;
   static final int DEFAULT_SCOPE_DEPTH_LIMIT = 100;
   static final int DEFAULT_SCOPE_ITERATION_KEEP_ALIVE = 30; // in seconds

dd-trace-api/src/main/java/datadog/trace/api/config/TracerConfig.java

@@ -73,6 +73,7 @@ public final class TracerConfig {
   public static final String TRACE_HTTP_CLIENT_ERROR_STATUSES = "trace.http.client.error.statuses";
 
   public static final String SPLIT_BY_TAGS = "trace.split-by-tags";
+  // trace latency interceptor value should be in ms
   public static final String TRACE_LATENCY_INTERCEPTOR_VALUE = "trace.latency.interceptor.value";
   public static final String SCOPE_DEPTH_LIMIT = "trace.scope.depth.limit";
   public static final String SCOPE_STRICT_MODE = "trace.scope.strict.mode";

dd-trace-core/src/main/java/datadog/trace/core/traceinterceptor/LatencyTraceInterceptor.java

@@ -9,6 +9,16 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+// This trace latency interceptor is disabled by default.
+// We can activate it by setting the value of dd.trace.latency.interceptor.value to a positive value
+// This value should be in milliseconds and this interceptor will retain any local trace who has a
+// root
+// span duration greater than this value.
+// The activation of this interceptor is ignored if partial flush is enabled.
+// Note that since we're changing the sampling priority at the end of local trace, there is no
+// guarantee to get complete traces,
+// since the original sampling priority for this trace may have been already propagated.
+
 public class LatencyTraceInterceptor extends AbstractTraceInterceptor {
   private static final Logger log = LoggerFactory.getLogger(LatencyTraceInterceptor.class);
   // duration configured in ms, need to be converted in nano seconds

dd-trace-core/src/test/groovy/datadog/trace/core/traceinterceptor/LatencyTraceInterceptorTest.groovy

@@ -45,6 +45,4 @@ class LatencyTraceInterceptorTest  extends DDCoreSpecification {
     "false"             |       "200"      | DDTags.MANUAL_KEEP            |   300          |   2
     "false"             |       "200"      | DDTags.MANUAL_DROP            |   300          |   2
   }
-
-
 }