Implemented default LoggingExporter for trace api

scm-webapp/src/main/java/sonia/scm/trace/LoggingExporter.java

@@ -0,0 +1,78 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package sonia.scm.trace;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import sonia.scm.plugin.Extension;
+
+import javax.inject.Inject;
+import java.util.Map;
+import java.util.function.Consumer;
+
+/**
+ * An {@link Exporter} which logs every collected span.
+ *
+ * @since 2.9.0
+ */
+@Extension
+public final class LoggingExporter implements Exporter {
+
+  private static final Logger LOG = LoggerFactory.getLogger(LoggingExporter.class);
+
+  private final Consumer<String> logger;
+
+  @Inject
+  LoggingExporter() {
+    this(LOG::info);
+  }
+
+  LoggingExporter(Consumer<String> logger) {
+    this.logger = logger;
+  }
+
+  @Override
+  public void export(SpanContext span) {
+    logger.accept(format(span));
+  }
+
+  private String format(SpanContext span) {
+    StringBuilder message = new StringBuilder("received ");
+    if (span.isFailed()) {
+      message.append("failed ");
+    }
+    message.append(span.getKind()).append(" span, which took ");
+    message.append(span.duration().toMillis()).append("ms");
+    Map<String, String> labels = span.getLabels();
+    if (!labels.isEmpty()) {
+      message.append(":");
+      for (Map.Entry<String, String> e : labels.entrySet()) {
+        message.append("\n - ").append(e.getKey()).append(": ").append(e.getValue());
+      }
+    }
+    return message.toString();
+  }
+
+}