external/bsd/openldap/dist/servers/slapd/back-bdb/trans.c

   1 /* trans.c - bdb backend transaction routines */
   2 /* $OpenLDAP: pkg/ldap/servers/slapd/back-bdb/trans.c,v 1.8.2.3 2008/02/11 23:26:46 kurt Exp $ */
   3 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
   4  *
   5  * Copyright 2000-2008 The OpenLDAP Foundation.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted only as authorized by the OpenLDAP
  10  * Public License.
  11  *
  12  * A copy of this license is available in the file LICENSE in the
  13  * top-level directory of the distribution or, alternatively, at
  14  * <http://www.OpenLDAP.org/license.html>.
  15  */
  16
  17 #include "portable.h"
  18
  19 #include <stdio.h>
  20 #include <ac/string.h>
  21
  22 #include "back-bdb.h"
  23 #include "lber_pvt.h"
  24 #include "lutil.h"
  25
  26
  27 /* Congestion avoidance code
  28  * for Deadlock Rollback
  29  */
  30
  31 void
  32 bdb_trans_backoff( int num_retries )
  33 {
  34         int i;
  35         int delay = 0;
  36         int pow_retries = 1;
  37         unsigned long key = 0;
  38         unsigned long max_key = -1;
  39         struct timeval timeout;
  40
  41         lutil_entropy( (unsigned char *) &key, sizeof( unsigned long ));
  42
  43         for ( i = 0; i < num_retries; i++ ) {
  44                 if ( i >= 5 ) break;
  45                 pow_retries *= 4;
  46         }
  47
  48         delay = 16384 * (key * (double) pow_retries / (double) max_key);
  49         delay = delay ? delay : 1;
  50
  51         Debug( LDAP_DEBUG_TRACE,  "delay = %d, num_retries = %d\n", delay, num_retries, 0 );
  52
  53         timeout.tv_sec = delay / 1000000;
  54         timeout.tv_usec = delay % 1000000;
  55         select( 0, NULL, NULL, NULL, &timeout );
  56 }