Berkeley DB congestion avoidance

servers/slapd/back-bdb/Makefile.in

@@ -6,12 +6,12 @@ SRCS = init.c tools.c config.c \
 	add.c bind.c compare.c delete.c modify.c modrdn.c search.c \
 	extended.c passwd.c referral.c operational.c \
 	attr.c index.c key.c dbcache.c filterindex.c \
-	dn2entry.c dn2id.c error.c id2entry.c idl.c nextid.c cache.c
+	dn2entry.c dn2id.c error.c id2entry.c idl.c nextid.c cache.c trans.c
 OBJS = init.lo tools.lo config.lo \
 	add.lo bind.lo compare.lo delete.lo modify.lo modrdn.lo search.lo \
 	extended.lo passwd.lo referral.lo operational.lo \
 	attr.lo index.lo key.lo dbcache.lo filterindex.lo \
-	dn2entry.lo dn2id.lo error.lo id2entry.lo idl.lo nextid.lo cache.lo
+	dn2entry.lo dn2id.lo error.lo id2entry.lo idl.lo nextid.lo cache.lo trans.lo
 
 LDAP_INCDIR= ../../../include       
 LDAP_LIBDIR= ../../../libraries

servers/slapd/back-bdb/add.c

@@ -33,6 +33,8 @@ bdb_add(Operation *op, SlapReply *rs )
 	DB_LOCK		lock;
 	int		noop = 0;
 
+	int		num_retries = 0;
+
 #ifdef LDAP_SYNC
 	Operation* ps_list;
 #endif
@@ -96,6 +98,7 @@ retry:	/* transaction retry */
 			rs->sr_text = "internal error";
 			goto return_results;
 		}
+		bdb_trans_backoff( ++num_retries );
 		ldap_pvt_thread_yield();
 	}
 

servers/slapd/back-bdb/delete.c

@@ -33,6 +33,8 @@ bdb_delete( Operation *op, SlapReply *rs )
 
 	int		noop = 0;
 
+	int		num_retries = 0;
+
 #ifdef LDAP_SYNC
 	Operation* ps_list;
 #endif
@@ -66,6 +68,7 @@ retry:	/* transaction retry */
 			rs->sr_text = "internal error";
 			goto return_results;
 		}
+		bdb_trans_backoff( ++num_retries );
 		ldap_pvt_thread_yield();
 	}
 

servers/slapd/back-bdb/modify.c

@@ -304,6 +304,8 @@ bdb_modify( Operation *op, SlapReply *rs )
 
 	int		noop = 0;
 
+	int		num_retries = 0;
+
 #ifdef LDAP_SYNC
 	Operation* ps_list;
 	struct psid_entry *pm_list, *pm_prev;
@@ -347,6 +349,7 @@ retry:	/* transaction retry */
 			rs->sr_text = "internal error";
 			goto return_results;
 		}
+		bdb_trans_backoff( ++num_retries );
 		ldap_pvt_thread_yield();
 	}
 

servers/slapd/back-bdb/modrdn.c

@@ -51,6 +51,8 @@ bdb_modrdn( Operation	*op, SlapReply *rs )
 
 	int		noop = 0;
 
+	int		num_retries = 0;
+
 #ifdef LDAP_SYNC
         Operation *ps_list;
 	struct psid_entry *pm_list, *pm_prev;
@@ -105,6 +107,7 @@ retry:	/* transaction retry */
 			rs->sr_text = "internal error";
 			goto return_results;
 		}
+		bdb_trans_backoff( ++num_retries );
 		ldap_pvt_thread_yield();
 	}
 

servers/slapd/back-bdb/passwd.c

@@ -36,6 +36,8 @@ bdb_exop_passwd( Operation *op, SlapReply *rs )
 	u_int32_t	locker = 0;
 	DB_LOCK		lock;
 
+	int		num_retries = 0;
+
 	assert( ber_bvcmp( &slap_EXOP_MODIFY_PASSWD, &op->oq_extended.rs_reqoid ) == 0 );
 
 	rc = slap_passwd_parse( op->oq_extended.rs_reqdata,
@@ -118,6 +120,7 @@ retry:	/* transaction retry */
 			rs->sr_text = "internal error";
 			goto done;
 		}
+		bdb_trans_backoff( ++num_retries );
 		ldap_pvt_thread_yield();
 	}
 

servers/slapd/back-bdb/proto-bdb.h

@@ -540,6 +540,12 @@ bdb_send_ldap_intermediate(
 	struct berval *cookie );
 #endif
 
+/*
+ * trans.c
+ */
+
+void
+bdb_trans_backoff( int num_retries );
 
 LDAP_END_DECL
 

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 );
+}

servers/slapd/proto-slap.h

@@ -1112,6 +1112,8 @@ LDAP_SLAPD_V (ldap_pvt_thread_mutex_t)	passwd_mutex;
 #endif
 LDAP_SLAPD_V (ldap_pvt_thread_mutex_t)	gmtime_mutex;
 
+LDAP_SLAPD_V (ldap_pvt_thread_mutex_t)	rand_mutex;
+
 LDAP_SLAPD_V (AccessControl *) global_acl;
 
 LDAP_SLAPD_V (ber_socket_t)	dtblsize;