HADOOP-7487. DF should throw a more reasonable exception when mount cannot be determined. Contributed by Andrew Wang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1449992 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -387,6 +387,9 @@ Release 2.0.4-beta - UNRELEASED
 
     HADOOP-9323. Fix typos in API documentation. (suresh)
 
+    HADOOP-7487. DF should throw a more reasonable exception when mount cannot
+    be determined. (Andrew Wang via atm)
+
 Release 2.0.3-alpha - 2013-02-06 
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/DF.java

@@ -17,19 +17,22 @@
  */
 package org.apache.hadoop.fs;
 
-import java.io.File;
-import java.io.IOException;
 import java.io.BufferedReader;
-
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.ArrayList;
 import java.util.EnumSet;
+import java.util.NoSuchElementException;
 import java.util.StringTokenizer;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.util.Shell;
 
+import com.google.common.annotations.VisibleForTesting;
+
 /** Filesystem disk space usage statistics.
  * Uses the unix 'df' program to get mount points, and java.io.File for
  * space utilization. Tested on Linux, FreeBSD, Cygwin. */
@@ -45,6 +48,8 @@ public class DF extends Shell {
   private String filesystem;
   private String mount;
   
+  private ArrayList<String> output;
+
   enum OSType {
     OS_TYPE_UNIX("UNIX"),
     OS_TYPE_WIN("Windows"),
@@ -84,6 +89,7 @@ public class DF extends Shell {
     super(dfInterval);
     this.dirPath = path.getCanonicalPath();
     this.dirFile = new File(this.dirPath);
+    this.output = new ArrayList<String>();
   }
 
   protected OSType getOSType() {
@@ -127,7 +133,21 @@ public class DF extends Shell {
 
   /** @return the filesystem mount point for the indicated volume */
   public String getMount() throws IOException {
+    // Abort early if specified path does not exist
+    if (!dirFile.exists()) {
+      throw new FileNotFoundException("Specified path " + dirFile.getPath()
+          + "does not exist");
+    }
     run();
+    // Skip parsing if df was not successful
+    if (getExitCode() != 0) {
+      StringBuffer sb = new StringBuffer("df could not be run successfully: ");
+      for (String line: output) {
+        sb.append(line);
+      }
+      throw new IOException(sb.toString());
+    }
+    parseOutput();
     return mount;
   }
   
@@ -152,24 +172,44 @@ public class DF extends Shell {
 
   @Override
   protected void parseExecResult(BufferedReader lines) throws IOException {
-    lines.readLine();                         // skip headings
-  
+    output.clear();
     String line = lines.readLine();
-    if (line == null) {
-      throw new IOException( "Expecting a line not the end of stream" );
+    while (line != null) {
+      output.add(line);
+      line = lines.readLine();
     }
+  }
+  
+  @VisibleForTesting
+  protected void parseOutput() throws IOException {
+    if (output.size() < 2) {
+      StringBuffer sb = new StringBuffer("Fewer lines of output than expected");
+      if (output.size() > 0) {
+        sb.append(": " + output.get(0));
+      }
+      throw new IOException(sb.toString());
+    }
+    
+    String line = output.get(1);
     StringTokenizer tokens =
       new StringTokenizer(line, " \t\n\r\f%");
     
+    try {
       this.filesystem = tokens.nextToken();
+    } catch (NoSuchElementException e) {
+      throw new IOException("Unexpected empty line");
+    }
     if (!tokens.hasMoreTokens()) {            // for long filesystem name
-      line = lines.readLine();
-      if (line == null) {
-        throw new IOException( "Expecting a line not the end of stream" );
+      if (output.size() > 2) {
+        line = output.get(2);
+      } else {
+        throw new IOException("Expecting additional output after line: "
+            + line);
       }
       tokens = new StringTokenizer(line, " \t\n\r\f%");
     }
 
+    try {
       switch(getOSType()) {
         case OS_TYPE_AIX:
           Long.parseLong(tokens.nextToken()); // capacity
@@ -192,6 +232,11 @@ public class DF extends Shell {
           this.mount = tokens.nextToken();
           break;
      }
+    } catch (NoSuchElementException e) {
+      throw new IOException("Could not parse line: " + line);
+    } catch (NumberFormatException e) {
+      throw new IOException("Could not parse line: " + line);
+    }
   }
 
   public static void main(String[] args) throws Exception {

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestDFVariations.java

@@ -17,15 +17,22 @@
 */
 package org.apache.hadoop.fs;
 
-import junit.framework.TestCase;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 
+import java.io.BufferedReader;
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.io.StringReader;
 import java.util.EnumSet;
+import java.util.Random;
 
+import org.apache.hadoop.test.GenericTestUtils;
 import org.apache.hadoop.util.Shell;
+import org.junit.Test;
 
-public class TestDFVariations extends TestCase {
+public class TestDFVariations {
 
   public static class XXDF extends DF {
     private final String osName;
@@ -50,6 +57,7 @@ public class TestDFVariations extends TestCase {
     }
   }
 
+  @Test(timeout=5000)
   public void testOSParsing() throws Exception {
     for (DF.OSType ost : EnumSet.allOf(DF.OSType.class)) {
       XXDF df = new XXDF(ost.getId());
@@ -59,5 +67,73 @@ public class TestDFVariations extends TestCase {
     }
   }
   
+  @Test(timeout=5000)
+  public void testDFInvalidPath() throws Exception {
+    // Generate a path that doesn't exist
+    Random random = new Random(0xDEADBEEFl);
+    File file = null;
+    byte[] bytes = new byte[64];
+    while (file == null) {
+      random.nextBytes(bytes);
+      final String invalid = new String("/" + bytes);
+      final File invalidFile = new File(invalid);
+      if (!invalidFile.exists()) {
+        file = invalidFile;
+      }
+    }
+    DF df = new DF(file, 0l);
+    try {
+      df.getMount();
+    } catch (FileNotFoundException e) {
+      // expected, since path does not exist
+      GenericTestUtils.assertExceptionContains(file.getName(), e);
+    }
+  }
+  
+  @Test(timeout=5000)
+  public void testDFMalformedOutput() throws Exception {
+    DF df = new DF(new File("/"), 0l);
+    BufferedReader reader = new BufferedReader(new StringReader(
+        "Filesystem     1K-blocks     Used Available Use% Mounted on\n" +
+        "/dev/sda5       19222656 10597036   7649060  59% /"));
+    df.parseExecResult(reader);
+    df.parseOutput();
+    
+    reader = new BufferedReader(new StringReader(
+        "Filesystem     1K-blocks     Used Available Use% Mounted on"));
+    df.parseExecResult(reader);
+    try {
+      df.parseOutput();
+      fail("Expected exception with missing line!");
+    } catch (IOException e) {
+      GenericTestUtils.assertExceptionContains(
+          "Fewer lines of output than expected", e);
+      System.out.println(e.toString());
+    }
+    
+    reader = new BufferedReader(new StringReader(
+        "Filesystem     1K-blocks     Used Available Use% Mounted on\n" +
+        " "));
+    df.parseExecResult(reader);
+    try {
+      df.parseOutput();
+      fail("Expected exception with empty line!");
+    } catch (IOException e) {
+      GenericTestUtils.assertExceptionContains("Unexpected empty line", e);
+      System.out.println(e.toString());
+    }
+    
+    reader = new BufferedReader(new StringReader(
+        "Filesystem     1K-blocks     Used Available Use% Mounted on\n" +
+        "       19222656 10597036   7649060  59% /"));
+    df.parseExecResult(reader);
+    try {
+      df.parseOutput();
+      fail("Expected exception with missing field!");
+    } catch (IOException e) {
+      GenericTestUtils.assertExceptionContains("Could not parse line: ", e);
+      System.out.println(e.toString());
+    }
+  }
 }