[ZOOKEEPER-4243] Resource leaks in org.apache.zookeeper.server.persistence.SnapStream#getInputStream and #getOutputStream

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Component/s: server
• Assignee: Unassigned
• Reporter: Martin Kellogg
• Created: 11/Mar/21 22:31
• Updated: 25/Mar/21 10:43
• Resolved: 25/Mar/21 10:43

Description

There are three (related) possible resource leaks in the getInputStream and getOutputStream methods in SnapStream.java. I noticed the first because of the use of the error-prone GZIPOutputStream, and the other two after looking at the surrounding code.

Here is the offending code (copied from https://github.com/apache/zookeeper/blob/master/zookeeper-server/src/main/java/org/apache/zookeeper/server/persistence/SnapStream.java#L102):

 

/**     
  * Return the CheckedInputStream based on the extension of the fileName.
  *     
  * @param file the file the InputStream read from
  * @return the specific InputStream     
  * @throws IOException    
  */    
public static CheckedInputStream getInputStream(File file) throws IOException {          
    FileInputStream fis = new FileInputStream(file);
    InputStream is; 
    switch (getStreamMode(file.getName())) { 
    case GZIP:            
        is = new GZIPInputStream(fis);
        break;        
    case SNAPPY:    
        is = new SnappyInputStream(fis);  
        break;        
    case CHECKED:       
    default:            
        is = new BufferedInputStream(fis);
    }        
    return new CheckedInputStream(is, new Adler32());
}
    
/**     
  * Return the OutputStream based on predefined stream mode.     
  *     
  * @param file the file the OutputStream writes to     
  * @param fsync sync the file immediately after write     
  * @return the specific OutputStream     
  * @throws IOException     
  */    
public static CheckedOutputStream getOutputStream(File file, boolean fsync) throws IOException {        
    OutputStream fos = fsync ? new AtomicFileOutputStream(file) : new FileOutputStream(file);        
    OutputStream os;        
    switch (streamMode) {        
        case GZIP:            
        os = new GZIPOutputStream(fos);  
        break;    
    case SNAPPY:        
        os = new SnappyOutputStream(fos);  
        break;        
    case CHECKED:       
    default:             
        os = new BufferedOutputStream(fos); 
    }       
    return new CheckedOutputStream(os, new Adler32());  
}

All three possible resource leaks are caused by the constructors of the intermediate streams (i.e. is and os), some of which might throw IOExceptions:

• in getOutputStream, the call to "new GZIPOutputStream" can throw an exception, because GZIPOutputStream writes out the header in the constructor. If it does throw, then fos is never closed. That it does so makes it hard to use correctly; someone raised this as an issue with the JDK folks [here|https://bugs.openjdk.java.net/browse/JDK-8180899], but they closed it as "won't fix" because the constructor is documented to throw (hence why we need to catch the exception here).
• in getInputStream, the call to "new GZIPInputStream" can throw an IOException for a similar reason, causing the file handle held by fis to leak.
• similarly, the call to "new SnappyInputStream" can throw an IOException, because it tries to read the file header during construction, which also causes fis to leak. SnappyOutputStream cannot throw; I checked [here|https://github.com/xerial/snappy-java/blob/master/src/main/java/org/xerial/snappy/SnappyOutputStream.java].

I will submit a PR with a fix on Github shortly and update this description with a link.

Issue Links

• duplicates: ZOOKEEPER-4246 Resource leaks in org.apache.zookeeper.server.persistence.SnapStream#getInputStream and #getOutputStream