dsdb-schema: do not reload more often than schema_reload_interval

Samba 4 use to try to reload the schema every time dsdb_get_schema was
called (which could be 20+ time per ldb request). Now we only reload at
most every xx seconds (xx being the value of dsdb:"schema_reload_interval"
 or 120). The timestamp of the last reloaded schema is kept in the
 dsdb_schema object. There is also a timestamp in the ldb_context, that
 is used by the LDAP server to know if it has to reload the schema after
 handling the request. This is used to allow that the schema will be
 immediately reload after a schemaUpdateNow request has been issued, the
 reload can't occur in the handling of the LDAP request itself because
 we have a transaction autostarted.

4 files changed, 42 insertions, 2 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/samldb.c b/source4/dsdb/samdb/ldb_modules/samldb.c
index 41c97bf32a..7b98dd62c1 100644
--- a/source4/dsdb/samdb/ldb_modules/samldb.c
+++ b/source4/dsdb/samdb/ldb_modules/samldb.c
@@ -4,6 +4,7 @@
    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005
    Copyright (C) Simo Sorce  2004-2008
    Copyright (C) Matthias Dieter Wallnöfer 2009-2011
+   Copyright (C) Matthieu Patou 2012
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -428,6 +429,8 @@ static int samldb_add_handle_msDS_IntId(struct samldb_ctx *ac)
 	struct ldb_context *ldb;
 	struct ldb_result *ldb_res;
 	struct ldb_dn *schema_dn;
+	struct samldb_msds_intid_persistant *msds_intid_struct;
+	struct dsdb_schema *schema;
 
 	ldb = ldb_module_get_ctx(ac->module);
 	schema_dn = ldb_get_schema_basedn(ldb);
diff --git a/source4/dsdb/samdb/ldb_modules/schema_load.c b/source4/dsdb/samdb/ldb_modules/schema_load.c
index 4c166d51ce..f922aabba9 100644
--- a/source4/dsdb/samdb/ldb_modules/schema_load.c
+++ b/source4/dsdb/samdb/ldb_modules/schema_load.c
@@ -49,6 +49,10 @@ static struct dsdb_schema *dsdb_schema_refresh(struct ldb_module *module, struct
 	struct dsdb_control_current_partition *ctrl;
 	struct ldb_context *ldb = ldb_module_get_ctx(module);
 	struct dsdb_schema *new_schema;
+	int interval;
+	time_t ts, lastts;
+	struct loadparm_context *lp_ctx =
+		(struct loadparm_context *)ldb_get_opaque(ldb, "loadparm");
 	
 	struct schema_load_private_data *private_data = talloc_get_type(ldb_module_get_private(module), struct schema_load_private_data);
 	if (!private_data) {
@@ -61,6 +65,14 @@ static struct dsdb_schema *dsdb_schema_refresh(struct ldb_module *module, struct
 		return schema;
 	}
 
+	lastts = schema->last_refresh;
+	ts = time(NULL);
+	interval = lpcfg_parm_int(lp_ctx, NULL, "dsdb", "schema_reload_interval", 120);
+	if (lastts > (ts - interval)) {
+		DEBUG(11, ("Less than %d seconds since last reload, returning cached version ts = %d\n", interval, (int)lastts));
+		return schema;
+	}
+
 	res = talloc_zero(schema, struct ldb_result);
 	if (res == NULL) {
 		return NULL;
@@ -84,7 +96,16 @@ static struct dsdb_schema *dsdb_schema_refresh(struct ldb_module *module, struct
 		talloc_free(res);
 		return NULL;
 	}
-	
+
+	/*
+	 * We update right now the last refresh timestamp so that if
+	 * the schema partition hasn't change we don't keep on retrying.
+	 * Otherwise if the timestamp was update only when the schema has
+	 * actually changed (and therefor completely reloaded) we would
+	 * continue to hit the database to get the highest USN.
+	 */
+	schema->last_refresh = ts;
+
 	ctrl = talloc(treq, struct dsdb_control_current_partition);
 	if (!ctrl) {
 		talloc_free(res);
@@ -130,7 +151,7 @@ static struct dsdb_schema *dsdb_schema_refresh(struct ldb_module *module, struct
 	if (ret != LDB_SUCCESS) {
 		return schema;
 	}
-	
+
 	if (is_global_schema) {
 		dsdb_make_schema_global(ldb, new_schema);
 	}
@@ -226,6 +247,7 @@ static int dsdb_schema_from_db(struct ldb_module *module, struct ldb_dn *schema_
 	ret = dsdb_set_schema(ldb, (*schema));
 
 	(*schema)->refresh_in_progress = false;
+	(*schema)->last_refresh = time(NULL);
 
 	if (ret != LDB_SUCCESS) {
 		ldb_debug_set(ldb, LDB_DEBUG_FATAL,
@@ -324,9 +346,22 @@ static int schema_load_del_transaction(struct ldb_module *module)
 
 static int schema_load_extended(struct ldb_module *module, struct ldb_request *req)
 {
+	time_t *lastts;
+	struct ldb_context *ldb = ldb_module_get_ctx(module);
+	struct dsdb_schema *schema;
+
 	if (strcmp(req->op.extended.oid, DSDB_EXTENDED_SCHEMA_UPDATE_NOW_OID) != 0) {
 		return ldb_next_request(module, req);
 	}
+	lastts = (time_t *)ldb_get_opaque(ldb, DSDB_OPAQUE_LAST_SCHEMA_UPDATE_MSG_OPAQUE_NAME);
+	if (!lastts) {
+		lastts = talloc(ldb, time_t);
+	}
+	schema = dsdb_get_schema(ldb, NULL);
+	/* Force a refresh */
+	schema->last_refresh = 0;
+	*lastts = 0;
+	ldb_set_opaque(ldb, DSDB_OPAQUE_LAST_SCHEMA_UPDATE_MSG_OPAQUE_NAME, lastts);
 
 	/* This is a no-op.  We reload as soon as we can */
 	return ldb_module_done(req, NULL, NULL, LDB_SUCCESS);
diff --git a/source4/dsdb/samdb/samdb.h b/source4/dsdb/samdb/samdb.h
index 50f7bf7d13..2a4bd355eb 100644
--- a/source4/dsdb/samdb/samdb.h
+++ b/source4/dsdb/samdb/samdb.h
@@ -199,6 +199,7 @@ struct dsdb_extended_dn_store_format {
 	bool store_extended_dn_in_ldb;
 };
 
+#define DSDB_OPAQUE_LAST_SCHEMA_UPDATE_MSG_OPAQUE_NAME "DSDB_OPAQUE_LAST_SCHEMA_UPDATE"
 #define DSDB_OPAQUE_PARTITION_MODULE_MSG_OPAQUE_NAME "DSDB_OPAQUE_PARTITION_MODULE_MSG"
 
 /* this takes a struct dsdb_fsmo_extended_op */
diff --git a/source4/dsdb/schema/schema.h b/source4/dsdb/schema/schema.h
index b1ae76882a..d3dd035e01 100644
--- a/source4/dsdb/schema/schema.h
+++ b/source4/dsdb/schema/schema.h
@@ -245,6 +245,7 @@ struct dsdb_schema {
 	struct ldb_module *loaded_from_module;
 	struct dsdb_schema *(*refresh_fn)(struct ldb_module *module, struct dsdb_schema *schema, bool is_global_schema);
 	bool refresh_in_progress;
+	time_t last_refresh;
 	/* an 'opaque' sequence number that the reload function may also wish to use */
 	uint64_t reload_seq_number;