1 files changed, 61 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/trace/Sampler.java b/api/src/main/java/io/opencensus/trace/Sampler.java
new file mode 100644
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+++ b/api/src/main/java/io/opencensus/trace/Sampler.java
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2017, OpenCensus Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opencensus.trace;
+
+import java.util.List;
+import javax.annotation.Nullable;
+
+/**
+ * Sampler is used to make decisions on {@link Span} sampling.
+ *
+ * @since 0.5
+ */
+public abstract class Sampler {
+  /**
+   * Called during {@link Span} creation to make a sampling decision.
+   *
+   * @param parentContext the parent span's {@link SpanContext}. {@code null} if this is a root
+   *     span.
+   * @param hasRemoteParent {@code true} if the parent {@code Span} is remote. {@code null} if this
+   *     is a root span.
+   * @param traceId the {@link TraceId} for the new {@code Span}. This will be identical to that in
+   *     the parentContext, unless this is a root span.
+   * @param spanId the {@link SpanId} for the new {@code Span}.
+   * @param name the name of the new {@code Span}.
+   * @param parentLinks the parentLinks associated with the new {@code Span}.
+   * @return {@code true} if the {@code Span} is sampled.
+   * @since 0.5
+   */
+  public abstract boolean shouldSample(
+      @Nullable SpanContext parentContext,
+      @Nullable Boolean hasRemoteParent,
+      TraceId traceId,
+      SpanId spanId,
+      String name,
+      List<Span> parentLinks);
+
+  /**
+   * Returns the description of this {@code Sampler}. This may be displayed on debug pages or in the
+   * logs.
+   *
+   * <p>Example: "ProbabilitySampler{0.000100}"
+   *
+   * @return the description of this {@code Sampler}.
+   * @since 0.6
+   */
+  public abstract String getDescription();
+}