RingBufferLogHandler


1   package hudson.util;
2   
3   import java.util.AbstractList  ;
4   import java.util.List  ;
5   import java.util.logging.Handler  ;
6   import java.util.logging.LogRecord  ;
7   
8   /**
9    * Log {@link Handler} that stores the log records into a ring buffer.
10   *
11   * @author Kohsuke Kawaguchi
12   */
13  public class RingBufferLogHandler extends Handler   {
14  
15      private int start = 0;
16      private final LogRecord  [] records;
17      private int size = 0;
18  
19      public RingBufferLogHandler() {
20          this(256);
21      }
22  
23      public RingBufferLogHandler(int ringSize) {
24          records = new LogRecord  [ringSize];
25      }
26  
27      public synchronized void publish(LogRecord   record) {
28          int len = records.length;
29          records[(start+size)%len]=record;
30          if(size==len) {
31              start++;
32          } else {
33              size++;
34          }
35      }
36  
37      /**
38       * Returns the list view of {@link LogRecord}s in the ring buffer.
39       *
40       * <p>
41       * New records are always placed early in the list.
42       */
43      public List  <LogRecord  > getView() {
44          return new AbstractList  <LogRecord  >() {
45              public LogRecord   get(int index) {
46                  // flip the order
47                  return records[(start+(size-(index+1)))%records.length];
48              }
49  
50              public int size() {
51                  return size;
52              }
53          };
54      }
55  
56      // noop
57      public void flush() {}
58      public void close() throws SecurityException   {}
59  }
60
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