Configure tags to be added to every span

dd-trace-ot/src/main/java/datadog/opentracing/DDSpanContext.java

@@ -148,7 +148,7 @@ public void setSpanType(final String spanType) {
     this.spanType = spanType;
   }
 
-  public void setSamplingPriority(int newPriority) {
+  public void setSamplingPriority(final int newPriority) {
     if (samplingPriorityLocked) {
       log.warn(
           "samplingPriority locked at {}. Refusing to set to {}", samplingPriority, newPriority);
@@ -272,7 +272,7 @@ public synchronized void setTag(final String tag, final Object value) {
 
   public synchronized Map<String, Object> getTags() {
     if (tags.isEmpty()) {
-      tags = Maps.newHashMapWithExpectedSize(2);
+      tags = Maps.newHashMapWithExpectedSize(3);
     }
     tags.put(DDTags.THREAD_NAME, threadName);
     tags.put(DDTags.THREAD_ID, threadId);

dd-trace-ot/src/main/java/datadog/opentracing/DDTracer.java

@@ -1,6 +1,7 @@
 package datadog.opentracing;
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.google.common.collect.Maps;
 import datadog.opentracing.decorators.AbstractDecorator;
 import datadog.opentracing.decorators.DDDecoratorsFactory;
 import datadog.opentracing.propagation.Codec;
@@ -44,6 +45,9 @@ public class DDTracer extends ThreadLocalScopeManager implements io.opentracing.
   /** Sampler defines the sampling policy in order to reduce the number of traces for instance */
   final Sampler sampler;
 
+  /** A set of tags that are added to every span */
+  private final Map<String, Object> spanTags;
+
   /** Span context decorators */
   private final Map<String, List<AbstractDecorator>> spanContextDecorators = new HashMap<>();
 
@@ -63,7 +67,8 @@ public DDTracer(final Properties config) {
     this(
         config.getProperty(DDTraceConfig.SERVICE_NAME),
         Writer.Builder.forConfig(config),
-        Sampler.Builder.forConfig(config));
+        Sampler.Builder.forConfig(config),
+        DDTraceConfig.parseMap(config.getProperty(DDTraceConfig.SPAN_TAGS)));
     log.debug("Using config: {}", config);
 
     // Create decorators from resource files
@@ -75,10 +80,20 @@ public DDTracer(final Properties config) {
   }
 
   public DDTracer(final String serviceName, final Writer writer, final Sampler sampler) {
+    this(serviceName, writer, sampler, Collections.<String, Object>emptyMap());
+  }
+
+  public DDTracer(
+      final String serviceName,
+      final Writer writer,
+      final Sampler sampler,
+      final Map<String, Object> spanTags) {
     this.serviceName = serviceName;
     this.writer = writer;
     this.writer.start();
     this.sampler = sampler;
+    this.spanTags = spanTags;
+
     registry = new CodecRegistry();
     registry.register(Format.Builtin.HTTP_HEADERS, new HTTPCodec());
     registry.register(Format.Builtin.TEXT_MAP, new HTTPCodec());
@@ -90,7 +105,11 @@ public DDTracer(final String serviceName, final Writer writer, final Sampler sam
   }
 
   public DDTracer(final Writer writer) {
-    this(UNASSIGNED_DEFAULT_SERVICE_NAME, writer, new AllSampler());
+    this(
+        UNASSIGNED_DEFAULT_SERVICE_NAME,
+        writer,
+        new AllSampler(),
+        DDTraceConfig.parseMap(new DDTraceConfig().getProperty(DDTraceConfig.SPAN_TAGS)));
   }
 
   /**
@@ -185,6 +204,8 @@ public String toString() {
         + writer
         + ", sampler="
         + sampler
+        + ", tags="
+        + spanTags
         + '}';
   }
 
@@ -236,7 +257,8 @@ public class DDSpanBuilder implements SpanBuilder {
     private final String operationName;
 
     // Builder attributes
-    private Map<String, Object> tags = Collections.emptyMap();
+    private Map<String, Object> tags =
+        spanTags.isEmpty() ? Collections.<String, Object>emptyMap() : Maps.newHashMap(spanTags);
     private long timestamp;
     private SpanContext parent;
     private String serviceName;
@@ -361,7 +383,7 @@ public DDSpanBuilder addReference(final String referenceType, final SpanContext
     // Private methods
     private DDSpanBuilder withTag(final String tag, final Object value) {
       if (this.tags.isEmpty()) {
-        this.tags = new HashMap<>();
+        this.tags = Maps.newHashMap();
       }
       this.tags.put(tag, value);
       return this;

dd-trace-ot/src/main/java/datadog/trace/common/DDTraceConfig.java

@@ -1,9 +1,13 @@
 package datadog.trace.common;
 
+import com.google.common.collect.Maps;
 import datadog.opentracing.DDTracer;
 import datadog.trace.common.writer.DDAgentWriter;
 import datadog.trace.common.writer.Writer;
+import java.util.Collections;
+import java.util.Map;
 import java.util.Properties;
+import lombok.extern.slf4j.Slf4j;
 
 /**
  * Config gives priority to system properties and falls back to environment variables. It also
@@ -14,6 +18,7 @@
  * <p>System properties are {@link DDTraceConfig#PREFIX}'ed. Environment variables are the same as
  * the system property, but uppercased with '.' -> '_'.
  */
+@Slf4j
 public class DDTraceConfig extends Properties {
   /** Config keys below */
   private static final String PREFIX = "dd.";
@@ -23,12 +28,14 @@ public class DDTraceConfig extends Properties {
   public static final String AGENT_HOST = "agent.host";
   public static final String AGENT_PORT = "agent.port";
   public static final String PRIORITY_SAMPLING = "priority.sampling";
+  public static final String SPAN_TAGS = "trace.span.tags";
 
   private final String serviceName = getPropOrEnv(PREFIX + SERVICE_NAME);
   private final String writerType = getPropOrEnv(PREFIX + WRITER_TYPE);
   private final String agentHost = getPropOrEnv(PREFIX + AGENT_HOST);
   private final String agentPort = getPropOrEnv(PREFIX + AGENT_PORT);
   private final String prioritySampling = getPropOrEnv(PREFIX + PRIORITY_SAMPLING);
+  private final String spanTags = getPropOrEnv(PREFIX + SPAN_TAGS);
 
   public DDTraceConfig() {
     super();
@@ -45,6 +52,7 @@ public DDTraceConfig() {
     setIfNotNull(AGENT_HOST, agentHost);
     setIfNotNull(AGENT_PORT, agentPort);
     setIfNotNull(PRIORITY_SAMPLING, prioritySampling);
+    setIfNotNull(SPAN_TAGS, spanTags);
   }
 
   public DDTraceConfig(final String serviceName) {
@@ -65,4 +73,23 @@ private String getPropOrEnv(final String name) {
   static String propToEnvName(final String name) {
     return name.toUpperCase().replace(".", "_");
   }
+
+  public static Map<String, Object> parseMap(final String str) {
+    if (str == null || str.trim().isEmpty()) {
+      return Collections.emptyMap();
+    }
+    if (!str.matches("(([^,:]+:[^,:]+,)*([^,:]+:[^,:]+),?)?")) {
+      log.warn("Invalid config '{}'. Must match 'key1:value1,key2:value2'.", str);
+      return Collections.emptyMap();
+    }
+
+    final String[] tokens = str.split(",");
+    final Map<String, Object> map = Maps.newHashMapWithExpectedSize(tokens.length);
+
+    for (final String token : tokens) {
+      final String[] keyValue = token.split(":");
+      map.put(keyValue[0].trim(), keyValue[1].trim());
+    }
+    return Collections.unmodifiableMap(map);
+  }
 }