Added NoOpTracer

micrometer-tracing/src/main/java/io/micrometer/tracing/CurrentTraceContext.java

@@ -15,13 +15,13 @@
  */
 package io.micrometer.tracing;
 
+import io.micrometer.common.lang.Nullable;
+
 import java.io.Closeable;
 import java.util.concurrent.Callable;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 
-import io.micrometer.common.lang.Nullable;
-
 /**
  * This API was heavily influenced by Brave. Parts of its documentation were taken
  * directly from Brave.
@@ -35,6 +35,50 @@
  */
 public interface CurrentTraceContext {
 
+    /**
+     * A noop implementation.
+     */
+    CurrentTraceContext NOOP = new CurrentTraceContext() {
+        @Override
+        public TraceContext context() {
+            return TraceContext.NOOP;
+        }
+
+        @Override
+        public Scope newScope(TraceContext context) {
+            return () -> {
+
+            };
+        }
+
+        @Override
+        public Scope maybeScope(TraceContext context) {
+            return () -> {
+
+            };
+        }
+
+        @Override
+        public <C> Callable<C> wrap(Callable<C> task) {
+            return task;
+        }
+
+        @Override
+        public Runnable wrap(Runnable task) {
+            return task;
+        }
+
+        @Override
+        public Executor wrap(Executor delegate) {
+            return delegate;
+        }
+
+        @Override
+        public ExecutorService wrap(ExecutorService delegate) {
+            return delegate;
+        }
+    };
+
     /**
      * @return current {@link TraceContext} or {@code null} if not set.
      */

micrometer-tracing/src/main/java/io/micrometer/tracing/ScopedSpan.java

@@ -24,6 +24,46 @@
  */
 public interface ScopedSpan {
 
+    /**
+     * A noop implementation.
+     */
+    ScopedSpan NOOP = new ScopedSpan() {
+        @Override
+        public boolean isNoop() {
+            return true;
+        }
+
+        @Override
+        public TraceContext context() {
+            return TraceContext.NOOP;
+        }
+
+        @Override
+        public ScopedSpan name(String name) {
+            return this;
+        }
+
+        @Override
+        public ScopedSpan tag(String key, String value) {
+            return this;
+        }
+
+        @Override
+        public ScopedSpan event(String value) {
+            return this;
+        }
+
+        @Override
+        public ScopedSpan error(Throwable throwable) {
+            return this;
+        }
+
+        @Override
+        public void end() {
+
+        }
+    };
+
     /**
      * @return {@code true} when no recording is done and nothing is reported to an
      * external system. However, this span should still be injected into outgoing

micrometer-tracing/src/main/java/io/micrometer/tracing/Span.java

@@ -15,10 +15,10 @@
  */
 package io.micrometer.tracing;
 
-import java.util.concurrent.TimeUnit;
-
 import io.micrometer.tracing.propagation.Propagator;
 
+import java.util.concurrent.TimeUnit;
+
 /**
  * This API was heavily influenced by Brave. Parts of its documentation were taken
  * directly from Brave.
@@ -32,6 +32,76 @@
  */
 public interface Span extends io.micrometer.tracing.SpanCustomizer {
 
+    /**
+     * A noop implementation.
+     */
+    Span NOOP = new Span() {
+        @Override
+        public boolean isNoop() {
+            return true;
+        }
+
+        @Override
+        public TraceContext context() {
+            return TraceContext.NOOP;
+        }
+
+        @Override
+        public Span start() {
+            return this;
+        }
+
+        @Override
+        public Span name(String name) {
+            return this;
+        }
+
+        @Override
+        public Span event(String value) {
+            return this;
+        }
+
+        @Override
+        public Span event(String value, long time, TimeUnit timeUnit) {
+            return this;
+        }
+
+        @Override
+        public Span tag(String key, String value) {
+            return this;
+        }
+
+        @Override
+        public Span error(Throwable throwable) {
+            return this;
+        }
+
+        @Override
+        public void end() {
+
+        }
+
+        @Override
+        public void end(long time, TimeUnit timeUnit) {
+
+        }
+
+        @Override
+        public void abandon() {
+
+        }
+
+        @Override
+        public Span remoteServiceName(String remoteServiceName) {
+            return this;
+        }
+
+        @Override
+        public Span remoteIpAndPort(String ip, int port) {
+            return this;
+        }
+    };
+
     /**
      * @return {@code true} when no recording is done and nothing is reported to an
      * external system. However, this span should still be injected into outgoing
@@ -168,6 +238,66 @@ enum Kind {
      */
     interface Builder {
 
+        /**
+         * A noop implementation.
+         */
+        Builder NOOP = new Builder() {
+            @Override
+            public Builder setParent(TraceContext context) {
+                return this;
+            }
+
+            @Override
+            public Builder setNoParent() {
+                return this;
+            }
+
+            @Override
+            public Builder name(String name) {
+                return this;
+            }
+
+            @Override
+            public Builder event(String value) {
+                return this;
+            }
+
+            @Override
+            public Builder tag(String key, String value) {
+                return this;
+            }
+
+            @Override
+            public Builder error(Throwable throwable) {
+                return this;
+            }
+
+            @Override
+            public Builder kind(Kind spanKind) {
+                return this;
+            }
+
+            @Override
+            public Builder remoteServiceName(String remoteServiceName) {
+                return this;
+            }
+
+            @Override
+            public Builder remoteIpAndPort(String ip, int port) {
+                return this;
+            }
+
+            @Override
+            public Builder startTimestamp(long startTimestamp, TimeUnit unit) {
+                return this;
+            }
+
+            @Override
+            public Span start() {
+                return Span.NOOP;
+            }
+        };
+
         /**
          * Sets the parent of the built span.
          * @param context parent's context

micrometer-tracing/src/main/java/io/micrometer/tracing/SpanCustomizer.java

@@ -24,6 +24,26 @@
  */
 public interface SpanCustomizer {
 
+    /**
+     * A noop implementation.
+     */
+    SpanCustomizer NOOP = new SpanCustomizer() {
+        @Override
+        public SpanCustomizer name(String name) {
+            return this;
+        }
+
+        @Override
+        public SpanCustomizer tag(String key, String value) {
+            return this;
+        }
+
+        @Override
+        public SpanCustomizer event(String value) {
+            return this;
+        }
+    };
+
     /**
      * Sets a name on a span.
      * @param name name to set on a span

micrometer-tracing/src/main/java/io/micrometer/tracing/TraceContext.java

@@ -25,6 +25,31 @@
  */
 public interface TraceContext {
 
+    /**
+     * A noop implementation.
+     */
+    TraceContext NOOP = new TraceContext() {
+        @Override
+        public String traceId() {
+            return "";
+        }
+
+        @Override
+        public String parentId() {
+            return null;
+        }
+
+        @Override
+        public String spanId() {
+            return "";
+        }
+
+        @Override
+        public Boolean sampled() {
+            return null;
+        }
+    };
+
     /**
      * Trace id.
      * @return trace id of a span
@@ -57,6 +82,36 @@ public interface TraceContext {
      */
     interface Builder {
 
+        /**
+         * A noop implementation.
+         */
+        Builder NOOP = new Builder() {
+            @Override
+            public Builder traceId(String traceId) {
+                return this;
+            }
+
+            @Override
+            public Builder parentId(String parentId) {
+                return this;
+            }
+
+            @Override
+            public Builder spanId(String spanId) {
+                return this;
+            }
+
+            @Override
+            public Builder sampled(Boolean sampled) {
+                return this;
+            }
+
+            @Override
+            public TraceContext build() {
+                return TraceContext.NOOP;
+            }
+        };
+
         /**
          * Sets trace id on the trace context.
          * @param traceId trace id