tracing libraries must configure the tracer sampling mechanism so tha…

…t, by default, 1 trace per minute gets sent.

dd-trace-core/src/main/java/datadog/trace/common/sampling/Sampler.java

@@ -34,6 +34,10 @@ final class Builder {
     public static Sampler forConfig(final Config config, final TraceConfig traceConfig) {
       Sampler sampler;
       if (config != null) {
+        if(!config.isTraceEnabled() && config.areTracingDependantProductsEnabled()){
+          log.debug("APM is disabled. Only 1 trace per minute will be sent.");
+          return new ServiceAsmTimeTraceSampler();
+        }
         final Map<String, String> serviceRules = config.getTraceSamplingServiceRules();
         final Map<String, String> operationRules = config.getTraceSamplingOperationRules();
         List<? extends SamplingRule.TraceSamplingRule> traceSamplingRules;

dd-trace-core/src/main/java/datadog/trace/common/sampling/ServiceAsmTimeTraceSampler.java

@@ -0,0 +1,45 @@
+package datadog.trace.common.sampling;
+
+import datadog.trace.api.sampling.SamplingMechanism;
+import datadog.trace.core.CoreSpan;
+import datadog.trace.core.util.SimpleRateLimiter;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+
+public class ServiceAsmTimeTraceSampler implements Sampler, PrioritySampler {
+
+  private static final Logger log = LoggerFactory.getLogger(ServiceAsmTimeTraceSampler.class);
+
+  private final SimpleRateLimiter rateLimiter;
+
+  public ServiceAsmTimeTraceSampler() {
+    this.rateLimiter = new SimpleRateLimiter(60); //one per minute
+  }
+
+  @Override
+  public <T extends CoreSpan<T>> boolean sample(final T span) {
+    // Priority sampling sends all traces to the core agent, including traces marked dropped.
+    // This allows the core agent to collect stats on all traces.
+    return true;
+  }
+
+  @Override
+  public <T extends CoreSpan<T>> void setSamplingPriority(final T span) {
+
+    //TODO check how to short circuit this for ASM
+
+    if (rateLimiter.tryAcquire()) {
+      span.setSamplingPriority(
+          PrioritySampling.SAMPLER_KEEP,
+          SamplingMechanism.DEFAULT);
+    } else {
+      span.setSamplingPriority(
+          PrioritySampling.SAMPLER_DROP,
+          SamplingMechanism.DEFAULT);
+    }
+
+  }
+
+}