New API: add writer builder

dd-trace/src/main/java/datadog/trace/tracer/Tracer.java

@@ -3,7 +3,6 @@ package datadog.trace.tracer;
 import datadog.trace.api.Config;
 import datadog.trace.tracer.sampling.AllSampler;
 import datadog.trace.tracer.sampling.Sampler;
-import datadog.trace.tracer.writer.LoggingWriter;
 import datadog.trace.tracer.writer.Writer;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -40,7 +39,7 @@ public class Tracer {
     // TODO: implement and include "standard" interceptors
     this(
         config,
-        new LoggingWriter(),
+        Writer.Builder.forConfig(config),
         new AllSampler(),
         Collections.unmodifiableList(new ArrayList<>(interceptors)));
   }

dd-trace/src/main/java/datadog/trace/tracer/writer/AgentClient.java

@@ -16,6 +16,7 @@ import java.net.URL;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
+import lombok.Getter;
 import lombok.extern.slf4j.Slf4j;
 import org.msgpack.jackson.dataformat.MessagePackFactory;
 
@@ -41,12 +42,12 @@ class AgentClient {
   private static final LogRateLimiter LOG_RATE_LIMITER =
       new LogRateLimiter(log, MILLISECONDS_BETWEEN_ERROR_LOG);
 
-  private final URL tracesUrl;
+  @Getter private final URL agentUrl;
 
   AgentClient(final String host, final int port) {
     final String url = "http://" + host + ":" + port + TRACES_ENDPOINT;
     try {
-      tracesUrl = new URL(url);
+      agentUrl = new URL(url);
     } catch (final MalformedURLException e) {
       // This should essentially mean agent should bail out from installing, we cannot meaningfully
       // recover from this.
@@ -90,7 +91,7 @@ class AgentClient {
   }
 
   private HttpURLConnection createHttpConnection() throws IOException {
-    final HttpURLConnection connection = (HttpURLConnection) tracesUrl.openConnection();
+    final HttpURLConnection connection = (HttpURLConnection) agentUrl.openConnection();
     connection.setDoOutput(true);
     connection.setDoInput(true);
 

dd-trace/src/main/java/datadog/trace/tracer/writer/AgentWriter.java

@@ -1,6 +1,7 @@
 package datadog.trace.tracer.writer;
 
 import datadog.trace.tracer.Trace;
+import java.net.URL;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.ArrayBlockingQueue;
@@ -51,6 +52,11 @@ public class AgentWriter implements Writer {
     shutdownCallback = new ShutdownCallback(executorService);
   }
 
+  /** @return Datadog agwent URL. Visible for testing. */
+  URL getAgentUrl() {
+    return task.getClient().getAgentUrl();
+  }
+
   @Override
   public void write(final Trace trace) {
     if (trace.isValid()) {
@@ -95,7 +101,7 @@ public class AgentWriter implements Writer {
   private static final class TracesSendingTask implements Runnable {
 
     /** The Datadog agent client */
-    private final AgentClient client;
+    @Getter private final AgentClient client;
     /** Queue size */
     private final int queueSize;
     /** In memory collection of traces waiting for departure */

dd-trace/src/main/java/datadog/trace/tracer/writer/Writer.java

@@ -1,6 +1,9 @@
 package datadog.trace.tracer.writer;
 
+import datadog.trace.api.Config;
 import datadog.trace.tracer.Trace;
+import java.util.Properties;
+import lombok.extern.slf4j.Slf4j;
 
 /** A writer sends traces to some place. */
 public interface Writer {
@@ -32,4 +35,41 @@ public interface Writer {
    * connections and tasks
    */
   void close();
+
+  @Slf4j
+  final class Builder {
+
+    public static Writer forConfig(final Config config) {
+      if (config == null) {
+        // There is no way config is not create so getting here must be a code bug
+        throw new NullPointerException("Config is required to create writer");
+      }
+
+      final Writer writer;
+
+      final String configuredType = config.getWriterType();
+      if (Config.DD_AGENT_WRITER_TYPE.equals(configuredType)) {
+        writer = createAgentWriter(config);
+      } else if (Config.LOGGING_WRITER_TYPE.equals(configuredType)) {
+        writer = new LoggingWriter();
+      } else {
+        log.warn(
+            "Writer type not configured correctly: Type {} not recognized. Defaulting to AgentWriter.",
+            configuredType);
+        writer = createAgentWriter(config);
+      }
+
+      return writer;
+    }
+
+    public static Writer forConfig(final Properties config) {
+      return forConfig(Config.get(config));
+    }
+
+    private static Writer createAgentWriter(final Config config) {
+      return new AgentWriter(new AgentClient(config.getAgentHost(), config.getAgentPort()));
+    }
+
+    private Builder() {}
+  }
 }

dd-trace/src/test/groovy/datadog/trace/tracer/TracerTest.groovy

@@ -2,7 +2,7 @@ package datadog.trace.tracer
 
 import datadog.trace.api.Config
 import datadog.trace.tracer.sampling.AllSampler
-import datadog.trace.tracer.writer.LoggingWriter
+import datadog.trace.tracer.writer.AgentWriter
 import datadog.trace.tracer.writer.SampleRateByService
 import datadog.trace.tracer.writer.Writer
 import spock.lang.Shared
@@ -25,7 +25,7 @@ class TracerTest extends Specification {
     def tracer = new Tracer(config)
 
     then:
-    tracer.getWriter() instanceof LoggingWriter
+    tracer.getWriter() instanceof AgentWriter
     tracer.getSampler() instanceof AllSampler
     tracer.getInterceptors() == []
     tracer.getDefaultServiceName() == config.getServiceName()

dd-trace/src/test/groovy/datadog/trace/tracer/writer/AgentWriterTest.groovy

@@ -13,8 +13,12 @@ class AgentWriterTest extends Specification {
   // We make this slightly longer than flush time.
   private static final int FLUSH_DELAY = TimeUnit.SECONDS.toMillis(AgentWriter.FLUSH_TIME_SECONDS * 2)
 
+  private static final AGENT_URL = new URL("http://example.com")
+
   def sampleRateByService = Mock(SampleRateByService)
-  def client = Mock(AgentClient)
+  def client = Mock(AgentClient) {
+    getAgentUrl() >> AGENT_URL
+  }
 
   def "test happy path"() {
     setup:
@@ -109,6 +113,16 @@ class AgentWriterTest extends Specification {
     writer.close()
   }
 
+  def "test agent url getter"() {
+    setup:
+    def writer = new AgentWriter(client)
+
+    when:
+    def agentUrl = writer.getAgentUrl()
+
+    then:
+    agentUrl == AGENT_URL
+  }
 
   def "test default sample rate by service"() {
     setup:

dd-trace/src/test/groovy/datadog/trace/tracer/writer/WriterTest.groovy

@@ -0,0 +1,63 @@
+package datadog.trace.tracer.writer
+
+import datadog.trace.api.Config
+import spock.lang.Specification
+
+
+class WriterTest extends Specification {
+
+  def "test builder logging writer"() {
+    setup:
+    def config = Mock(Config) {
+      getWriterType() >> Config.LOGGING_WRITER_TYPE
+    }
+
+    when:
+    def writer = Writer.Builder.forConfig(config)
+
+    then:
+    writer instanceof LoggingWriter
+  }
+
+  def "test builder logging writer properties"() {
+    setup:
+    def properties = new Properties()
+    properties.setProperty(Config.WRITER_TYPE, Config.LOGGING_WRITER_TYPE)
+
+    when:
+    def writer = Writer.Builder.forConfig(properties)
+
+    then:
+    writer instanceof LoggingWriter
+  }
+
+  def "test builder agent writer: '#writerType'"() {
+    setup:
+    def config = Mock(Config) {
+      getWriterType() >> writerType
+      getAgentHost() >> "test.host"
+      getAgentPort() >> 1234
+    }
+
+    when:
+    def writer = Writer.Builder.forConfig(config)
+
+    then:
+    writer instanceof AgentWriter
+    ((AgentWriter) writer).getAgentUrl() == new URL("http://test.host:1234/v0.4/traces");
+
+    where:
+    writerType | _
+    Config.DD_AGENT_WRITER_TYPE | _
+    "some odd string" | _
+  }
+
+  def "test builder no config"() {
+    when:
+    Writer.Builder.forConfig(null)
+
+    then:
+    thrown NullPointerException
+  }
+
+}