HADOOP-18526. checkstyle and TRACE of stack in s3afs.initialize()

off by default...test/log4j.properties has it commented out

Change-Id: Ie83b74009ccae8869b2c5386206b913e0f76af2f

Author: steveloughran

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java

@@ -458,6 +458,12 @@ public void initialize(URI name, Configuration originalConf)
     AuditSpan span = null;
     try {
       LOG.debug("Initializing S3AFileSystem for {}", bucket);
+      if (LOG.isTraceEnabled()) {
+        // log a full trace for deep diagnostics of where an object is created,
+        // for tracking down memory leak issues.
+        LOG.trace("Filesystem for {} creation stack",
+            name, new RuntimeException(super.toString()));
+      }
       // clone the configuration into one with propagated bucket options
       Configuration conf = propagateBucketOptions(originalConf, bucket);
       // HADOOP-17894. remove references to s3a stores in JCEKS credentials.

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/TestInstrumentationLifecycle.java

@@ -22,7 +22,6 @@
 
 import org.junit.Test;
 
-import org.apache.hadoop.fs.statistics.StoreStatisticNames;
 import org.apache.hadoop.metrics2.MetricsSystem;
 import org.apache.hadoop.test.AbstractHadoopTestBase;
 

hadoop-tools/hadoop-aws/src/test/resources/log4j.properties

@@ -53,6 +53,8 @@ log4j.logger.org.apache.hadoop.ipc.Server=WARN
 # for debugging low level S3a operations, uncomment these lines
 # Log all S3A classes
 log4j.logger.org.apache.hadoop.fs.s3a=DEBUG
+# when logging at trace, the stack of the initialize() call is logged
+#log4j.logger.org.apache.hadoop.fs.s3a.S3AFileSystem=TRACE
 #log4j.logger.org.apache.hadoop.fs.s3a.S3AUtils=INFO
 #log4j.logger.org.apache.hadoop.fs.s3a.Listing=INFO
 log4j.logger.org.apache.hadoop.fs.s3a.SDKV2Upgrade=WARN