HTRACE-33 Add getUniqueLocalTraceFileName to LocalFileSpanReceiver (Masatake Iwasaki via Colin P. McCabe)
diff --git a/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java b/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java
index 8b037bf..09cbb01 100644
--- a/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java
+++ b/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java
@@ -24,10 +24,15 @@
 import org.apache.htrace.Span;
 import org.apache.htrace.SpanReceiver;
 
+import java.io.BufferedReader;
 import java.io.BufferedWriter;
-import java.io.FileOutputStream;
+import java.io.EOFException;
+import java.io.File;
+import java.io.FileInputStream;
 import java.io.FileWriter;
+import java.io.InputStreamReader;
 import java.io.IOException;
+import java.util.UUID;
 import java.io.OutputStreamWriter;
 import java.io.Writer;
 import java.util.concurrent.ExecutorService;
@@ -126,4 +131,37 @@
       LOG.error("Error closing writer for file: " + file, e);
     }
   }
+
+  public static String getUniqueLocalTraceFileName() {
+    String tmp = System.getProperty("java.io.tmpdir", "/tmp");
+    String nonce = null;
+    BufferedReader reader = null;
+    try {
+      // On Linux we can get a unique local file name by reading the process id
+      // out of /proc/self/stat.  (There isn't any portable way to get the
+      // process ID from Java.)
+      reader = new BufferedReader(
+          new InputStreamReader(new FileInputStream("/proc/self/stat"),
+                                "UTF-8"));
+      String line = reader.readLine();
+      if (line == null) {
+        throw new EOFException();
+      }
+      nonce = line.split(" ")[0];
+    } catch (IOException e) {
+    } finally {
+      if (reader != null) {
+        try {
+          reader.close();
+        } catch(IOException e) {
+          LOG.debug("Exception in closing " + reader, e);
+        }
+      }
+    }
+    if (nonce == null) {
+      // If we can't use the process ID, use a random nonce.
+      nonce = UUID.randomUUID().toString();
+    }
+    return new File(tmp, nonce).getAbsolutePath();
+  }
 }
diff --git a/htrace-core/src/test/java/org/apache/htrace/impl/TestLocalFileSpanReceiver.java b/htrace-core/src/test/java/org/apache/htrace/impl/TestLocalFileSpanReceiver.java
new file mode 100644
index 0000000..98dd951
--- /dev/null
+++ b/htrace-core/src/test/java/org/apache/htrace/impl/TestLocalFileSpanReceiver.java
@@ -0,0 +1,74 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.htrace.impl;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import java.io.File;
+import java.io.IOException;
+import java.util.HashMap;
+import org.apache.htrace.HTraceConfiguration;
+import org.apache.htrace.Sampler;
+import org.apache.htrace.Span;
+import org.apache.htrace.SpanReceiver;
+import org.apache.htrace.SpanReceiverBuilder;
+import org.apache.htrace.Trace;
+import org.apache.htrace.TraceScope;
+import org.junit.Ignore;
+import org.junit.Test;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertEquals;
+
+@Ignore
+public class TestLocalFileSpanReceiver {
+  @Test
+  public void testUniqueLocalTraceFileName() {
+    String filename1 = LocalFileSpanReceiver.getUniqueLocalTraceFileName();
+    System.out.println("##### :" + filename1);
+    String filename2 = LocalFileSpanReceiver.getUniqueLocalTraceFileName();
+    System.out.println("##### :" + filename2);
+    boolean eq = filename1.equals(filename2);
+    if (System.getProperty("os.name").startsWith("Linux")) {
+      // ${java.io.tmpdir}/[pid]
+      assertTrue(eq);
+    } else {
+      // ${java.io.tmpdir}/[random UUID]
+      assertFalse(eq);
+    }
+  }
+
+  @Test
+  public void testWriteToLocalFile() throws IOException {
+    String traceFileName = LocalFileSpanReceiver.getUniqueLocalTraceFileName();
+    HashMap<String, String> confMap = new HashMap<String, String>();
+    confMap.put(LocalFileSpanReceiver.PATH_KEY, traceFileName);
+    confMap.put(SpanReceiverBuilder.SPAN_RECEIVER_CONF_KEY,
+                LocalFileSpanReceiver.class.getName());
+    SpanReceiver rcvr =
+        new SpanReceiverBuilder(HTraceConfiguration.fromMap(confMap))
+            .logErrors(false).build();
+    Trace.addReceiver(rcvr);
+    TraceScope ts = Trace.startSpan("testWriteToLocalFile", Sampler.ALWAYS);
+    ts.close();
+    Trace.removeReceiver(rcvr);
+    rcvr.close();
+
+    ObjectMapper mapper = new ObjectMapper();
+    MilliSpan span = mapper.readValue(new File(traceFileName), MilliSpan.class);
+    assertEquals("testWriteToLocalFile", span.getDescription());
+  }
+}
diff --git a/pom.xml b/pom.xml
index a85149a..807b567 100644
--- a/pom.xml
+++ b/pom.xml
@@ -274,6 +274,9 @@
         <artifactId>maven-surefire-plugin</artifactId>
         <configuration>
           <redirectTestOutputToFile>true</redirectTestOutputToFile>
+          <systemPropertyVariables>
+            <java.io.tmpdir>${project.build.directory}</java.io.tmpdir>
+          </systemPropertyVariables>
         </configuration>
       </plugin>
     </plugins>