Berkeley DB congestion avoidance

[openldap] / servers / slapd / back-bdb / trans.c

diff --git a/servers/slapd/back-bdb/trans.c b/servers/slapd/back-bdb/trans.c
new file mode 100644 (file)
index 0000000..51fecf4
--- /dev/null
+++ b/servers/slapd/back-bdb/trans.c
@@ -0,0 +1,47 @@
+/* trans.c - bdb backend transaction routines */
+/* $OpenLDAP$ */
+
+#include "portable.h"
+
+#include <stdio.h>
+#include <ac/string.h>
+
+#include "back-bdb.h"
+#include "external.h"
+#include "lber_pvt.h"
+
+
+/* Congestion avoidance code
+ * for Deadlock Rollback
+ */
+
+void
+bdb_trans_backoff( int num_retries )
+{
+       int i;
+       int delay = 0;
+       int pow_retries = 1;
+       unsigned long key = 0;
+       unsigned long max_key = -1;
+       struct timeval timeout;
+
+       lutil_entropy( &key, sizeof( unsigned long ));
+
+       for ( i = 0; i < num_retries; i++ ) {
+               if ( i >= 5 ) break;
+               pow_retries *= 4;
+       }
+
+       delay = 16384 * (key * (double) pow_retries / (double) max_key);
+       delay = delay ? delay : 1;
+
+#ifdef NEW_LOGGING
+       LDAP_LOG( OPERATION, ERR, "delay = %d, num_retries = %d\n", delay, num_retries, 0 );
+#else
+       Debug( LDAP_DEBUG_TRACE,  "delay = %d, num_retries = %d\n", delay, num_retries, 0 );
+#endif
+
+       timeout.tv_sec = delay / 1000000;
+       timeout.tv_usec = delay % 1000000;
+       select( 0, NULL, NULL, NULL, &timeout );
+}