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/* $OpenLDAP$ */
/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
*
* Copyright 1998-2022 The OpenLDAP Foundation.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted only as authorized by the OpenLDAP
* Public License.
*
* A copy of this license is available in the file LICENSE in the
* top-level directory of the distribution or, alternatively, at
* <http://www.OpenLDAP.org/license.html>.
*/
#include "portable.h"
#include "lload.h"
static LloadTierInit roundrobin_init;
static LloadTierBackendCb roundrobin_add_backend;
static LloadTierBackendCb roundrobin_remove_backend;
static LloadTierSelect roundrobin_select;
struct lload_tier_type roundrobin_tier;
static LloadTier *
roundrobin_init( void )
{
LloadTier *tier;
tier = ch_calloc( 1, sizeof(LloadTier) );
tier->t_type = roundrobin_tier;
ldap_pvt_thread_mutex_init( &tier->t_mutex );
LDAP_CIRCLEQ_INIT( &tier->t_backends );
return tier;
}
static int
roundrobin_add_backend( LloadTier *tier, LloadBackend *b )
{
assert( b->b_tier == tier );
LDAP_CIRCLEQ_INSERT_TAIL( &tier->t_backends, b, b_next );
if ( !tier->t_private ) {
tier->t_private = b;
}
tier->t_nbackends++;
return LDAP_SUCCESS;
}
static int
roundrobin_remove_backend( LloadTier *tier, LloadBackend *b )
{
LloadBackend *next = LDAP_CIRCLEQ_LOOP_NEXT( &tier->t_backends, b, b_next );
assert_locked( &tier->t_mutex );
assert_locked( &b->b_mutex );
assert( b->b_tier == tier );
LDAP_CIRCLEQ_REMOVE( &tier->t_backends, b, b_next );
if ( b == tier->t_private ) {
if ( tier->t_nbackends ) {
tier->t_private = next;
} else {
assert( b == next );
tier->t_private = NULL;
}
}
tier->t_nbackends--;
return LDAP_SUCCESS;
}
static int
roundrobin_select(
LloadTier *tier,
LloadOperation *op,
LloadConnection **cp,
int *res,
char **message )
{
LloadBackend *b, *first, *next;
int rc = 0;
checked_lock( &tier->t_mutex );
first = b = tier->t_private;
checked_unlock( &tier->t_mutex );
if ( !first ) return rc;
do {
int result;
checked_lock( &b->b_mutex );
next = LDAP_CIRCLEQ_LOOP_NEXT( &tier->t_backends, b, b_next );
result = backend_select( b, op, cp, res, message );
checked_unlock( &b->b_mutex );
rc |= result;
if ( result && *cp ) {
/*
* Round-robin step:
* Rotate the queue to put this backend at the end. The race here
* is acceptable.
*/
checked_lock( &tier->t_mutex );
tier->t_private = next;
checked_unlock( &tier->t_mutex );
return rc;
}
b = next;
} while ( b != first );
return rc;
}
struct lload_tier_type roundrobin_tier = {
.tier_name = "roundrobin",
.tier_init = roundrobin_init,
.tier_startup = tier_startup,
.tier_reset = tier_reset,
.tier_destroy = tier_destroy,
.tier_oc = BER_BVC("olcBkLloadTierConfig"),
.tier_backend_oc = BER_BVC("olcBkLloadBackendConfig"),
.tier_add_backend = roundrobin_add_backend,
.tier_remove_backend = roundrobin_remove_backend,
.tier_select = roundrobin_select,
};
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