path: root/source4/cluster/ctdb/server/ctdb_ltdb_server.c

/* 
   ctdb ltdb code - server side

   Copyright (C) Andrew Tridgell  2007

   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
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "lib/events/events.h"
#include "lib/tdb/include/tdb.h"
#include "system/network.h"
#include "system/filesys.h"
#include "../include/ctdb_private.h"
#include "db_wrap.h"
#include "lib/util/dlinklist.h"

/*
  this is the dummy null procedure that all databases support
*/
static int ctdb_null_func(struct ctdb_call_info *call)
{
	return 0;
}

/*
  this is a plain fetch procedure that all databases support
*/
static int ctdb_fetch_func(struct ctdb_call_info *call)
{
	call->reply_data = &call->record_data;
	return 0;
}



struct lock_fetch_state {
	struct ctdb_context *ctdb;
	void (*recv_pkt)(void *, struct ctdb_req_header *);
	void *recv_context;
	struct ctdb_req_header *hdr;
	uint32_t generation;
	bool ignore_generation;
};

/*
  called when we should retry the operation
 */
static void lock_fetch_callback(void *p)
{
	struct lock_fetch_state *state = talloc_get_type(p, struct lock_fetch_state);
	if (!state->ignore_generation &&
	    state->generation != state->ctdb->vnn_map->generation) {
		DEBUG(0,("Discarding previous generation lockwait packet\n"));
		talloc_free(state->hdr);
		return;
	}
	state->recv_pkt(state->recv_context, state->hdr);
	DEBUG(2,(__location__ " PACKET REQUEUED\n"));
}


/*
  do a non-blocking ltdb_lock, deferring this ctdb request until we
  have the chainlock

  It does the following:

   1) tries to get the chainlock. If it succeeds, then it returns 0

   2) if it fails to get a chainlock immediately then it sets up a
   non-blocking chainlock via ctdb_lockwait, and when it gets the
   chainlock it re-submits this ctdb request to the main packet
   receive function

   This effectively queues all ctdb requests that cannot be
   immediately satisfied until it can get the lock. This means that
   the main ctdb daemon will not block waiting for a chainlock held by
   a client

   There are 3 possible return values:

       0:    means that it got the lock immediately.
      -1:    means that it failed to get the lock, and won't retry
      -2:    means that it failed to get the lock immediately, but will retry
 */
int ctdb_ltdb_lock_requeue(struct ctdb_db_context *ctdb_db, 
			   TDB_DATA key, struct ctdb_req_header *hdr,
			   void (*recv_pkt)(void *, struct ctdb_req_header *),
			   void *recv_context, bool ignore_generation)
{
	int ret;
	struct tdb_context *tdb = ctdb_db->ltdb->tdb;
	struct lockwait_handle *h;
	struct lock_fetch_state *state;
	
	ret = tdb_chainlock_nonblock(tdb, key);

	if (ret != 0 &&
	    !(errno == EACCES || errno == EAGAIN || errno == EDEADLK)) {
		/* a hard failure - don't try again */
		return -1;
	}

	/* when torturing, ensure we test the contended path */
	if ((ctdb_db->ctdb->flags & CTDB_FLAG_TORTURE) &&
	    random() % 5 == 0) {
		ret = -1;
		tdb_chainunlock(tdb, key);
	}

	/* first the non-contended path */
	if (ret == 0) {
		return 0;
	}

	state = talloc(hdr, struct lock_fetch_state);
	state->ctdb = ctdb_db->ctdb;
	state->hdr = hdr;
	state->recv_pkt = recv_pkt;
	state->recv_context = recv_context;
	state->generation = ctdb_db->ctdb->vnn_map->generation;
	state->ignore_generation = ignore_generation;

	/* now the contended path */
	h = ctdb_lockwait(ctdb_db, key, lock_fetch_callback, state);
	if (h == NULL) {
		tdb_chainunlock(tdb, key);
		return -1;
	}

	/* we need to move the packet off the temporary context in ctdb_input_pkt(),
	   so it won't be freed yet */
	talloc_steal(state, hdr);
	talloc_steal(state, h);

	/* now tell the caller than we will retry asynchronously */
	return -2;
}

/*
  a varient of ctdb_ltdb_lock_requeue that also fetches the record
 */
int ctdb_ltdb_lock_fetch_requeue(struct ctdb_db_context *ctdb_db, 
				 TDB_DATA key, struct ctdb_ltdb_header *header, 
				 struct ctdb_req_header *hdr, TDB_DATA *data,
				 void (*recv_pkt)(void *, struct ctdb_req_header *),
				 void *recv_context, bool ignore_generation)
{
	int ret;

	ret = ctdb_ltdb_lock_requeue(ctdb_db, key, hdr, recv_pkt, 
				     recv_context, ignore_generation);
	if (ret == 0) {
		ret = ctdb_ltdb_fetch(ctdb_db, key, header, hdr, data);
		if (ret != 0) {
			ctdb_ltdb_unlock(ctdb_db, key);
		}
	}
	return ret;
}


/*
  paraoid check to see if the db is empty
 */
static void ctdb_check_db_empty(struct ctdb_db_context *ctdb_db)
{
	struct tdb_context *tdb = ctdb_db->ltdb->tdb;
	int count = tdb_traverse_read(tdb, NULL, NULL);
	if (count != 0) {
		DEBUG(0,(__location__ " tdb '%s' not empty on attach! aborting\n",
			 ctdb_db->db_path));
		ctdb_fatal(ctdb_db->ctdb, "database not empty on attach");
	}
}

/*
  a client has asked to attach a new database
 */
int32_t ctdb_control_db_attach(struct ctdb_context *ctdb, TDB_DATA indata,
			       TDB_DATA *outdata)
{
	const char *db_name = (const char *)indata.dptr;
	struct ctdb_db_context *ctdb_db, *tmp_db;
	int ret;

	/* see if we already have this name */
	for (tmp_db=ctdb->db_list;tmp_db;tmp_db=tmp_db->next) {
		if (strcmp(db_name, tmp_db->db_name) == 0) {
			/* this is not an error */
			outdata->dptr  = (uint8_t *)&tmp_db->db_id;
			outdata->dsize = sizeof(tmp_db->db_id);
			return 0;
		}
	}

	ctdb_db = talloc_zero(ctdb, struct ctdb_db_context);
	CTDB_NO_MEMORY(ctdb, ctdb_db);

	ctdb_db->ctdb = ctdb;
	ctdb_db->db_name = talloc_strdup(ctdb_db, db_name);
	CTDB_NO_MEMORY(ctdb, ctdb_db->db_name);

	ctdb_db->db_id = ctdb_hash(&indata);

	outdata->dptr  = (uint8_t *)&ctdb_db->db_id;
	outdata->dsize = sizeof(ctdb_db->db_id);

	/* check for hash collisions */
	for (tmp_db=ctdb->db_list;tmp_db;tmp_db=tmp_db->next) {
		if (tmp_db->db_id == ctdb_db->db_id) {
			DEBUG(0,("db_id 0x%x hash collision. name1='%s' name2='%s'\n",
				 tmp_db->db_id, db_name, tmp_db->db_name));
			talloc_free(ctdb_db);
			return -1;
		}
	}

	if (ctdb->db_directory == NULL) {
		ctdb->db_directory = VARDIR "/ctdb";
	}

	/* make sure the db directory exists */
	if (mkdir(ctdb->db_directory, 0700) == -1 && errno != EEXIST) {
		DEBUG(0,(__location__ " Unable to create ctdb directory '%s'\n", 
			 ctdb->db_directory));
		talloc_free(ctdb_db);
		return -1;
	}

	/* open the database */
	ctdb_db->db_path = talloc_asprintf(ctdb_db, "%s/%s.%u", 
					   ctdb->db_directory, 
					   db_name, ctdb->vnn);

	ctdb_db->ltdb = tdb_wrap_open(ctdb, ctdb_db->db_path, 
				      ctdb->tunable.database_hash_size, 
				      TDB_CLEAR_IF_FIRST, O_CREAT|O_RDWR, 0666);
	if (ctdb_db->ltdb == NULL) {
		DEBUG(0,("Failed to open tdb '%s'\n", ctdb_db->db_path));
		talloc_free(ctdb_db);
		return -1;
	}

	ctdb_check_db_empty(ctdb_db);

	DLIST_ADD(ctdb->db_list, ctdb_db);

	/* 
	   all databases support the "null" function. we need this in
	   order to do forced migration of records
	*/
	ret = ctdb_daemon_set_call(ctdb, ctdb_db->db_id, ctdb_null_func, CTDB_NULL_FUNC);
	if (ret != 0) {
		DEBUG(0,("Failed to setup null function for '%s'\n", ctdb_db->db_name));
		talloc_free(ctdb_db);
		return -1;
	}

	/* 
	   all databases support the "fetch" function. we need this
	   for efficient Samba3 ctdb fetch
	*/
	ret = ctdb_daemon_set_call(ctdb, ctdb_db->db_id, ctdb_fetch_func, CTDB_FETCH_FUNC);
	if (ret != 0) {
		DEBUG(0,("Failed to setup fetch function for '%s'\n", ctdb_db->db_name));
		talloc_free(ctdb_db);
		return -1;
	}
	
	/* tell all the other nodes about this database */
	ctdb_daemon_send_control(ctdb, CTDB_BROADCAST_ALL, 0,
				 CTDB_CONTROL_DB_ATTACH, 0, CTDB_CTRL_FLAG_NOREPLY,
				 indata, NULL, NULL);

	DEBUG(1,("Attached to database '%s'\n", ctdb_db->db_path));

	/* success */
	return 0;
}

/*
  called when a broadcast seqnum update comes in
 */
int32_t ctdb_ltdb_update_seqnum(struct ctdb_context *ctdb, uint32_t db_id, uint32_t srcnode)
{
	struct ctdb_db_context *ctdb_db;
	if (srcnode == ctdb->vnn) {
		/* don't update ourselves! */
		return 0;
	}

	ctdb_db = find_ctdb_db(ctdb, db_id);
	if (!ctdb_db) {
		DEBUG(0,("Unknown db_id 0x%x in ctdb_ltdb_update_seqnum\n", db_id));
		return -1;
	}

	tdb_increment_seqnum_nonblock(ctdb_db->ltdb->tdb);
	ctdb_db->seqnum = tdb_get_seqnum(ctdb_db->ltdb->tdb);
	return 0;
}

/*
  timer to check for seqnum changes in a ltdb and propogate them
 */
static void ctdb_ltdb_seqnum_check(struct event_context *ev, struct timed_event *te, 
				   struct timeval t, void *p)
{
	struct ctdb_db_context *ctdb_db = talloc_get_type(p, struct ctdb_db_context);
	struct ctdb_context *ctdb = ctdb_db->ctdb;
	uint32_t new_seqnum = tdb_get_seqnum(ctdb_db->ltdb->tdb);
	if (new_seqnum != ctdb_db->seqnum) {
		/* something has changed - propogate it */
		TDB_DATA data;
		data.dptr = (uint8_t *)&ctdb_db->db_id;
		data.dsize = sizeof(uint32_t);
		ctdb_daemon_send_control(ctdb, CTDB_BROADCAST_VNNMAP, 0,
					 CTDB_CONTROL_UPDATE_SEQNUM, 0, CTDB_CTRL_FLAG_NOREPLY,
					 data, NULL, NULL);		
	}
	ctdb_db->seqnum = new_seqnum;

	/* setup a new timer */
	ctdb_db->te = 
		event_add_timed(ctdb->ev, ctdb_db, 
				timeval_current_ofs(ctdb->tunable.seqnum_frequency, 0),
				ctdb_ltdb_seqnum_check, ctdb_db);
}

/*
  enable seqnum handling on this db
 */
int32_t ctdb_ltdb_enable_seqnum(struct ctdb_context *ctdb, uint32_t db_id)
{
	struct ctdb_db_context *ctdb_db;
	ctdb_db = find_ctdb_db(ctdb, db_id);
	if (!ctdb_db) {
		DEBUG(0,("Unknown db_id 0x%x in ctdb_ltdb_enable_seqnum\n", db_id));
		return -1;
	}

	if (ctdb_db->te == NULL) {
		ctdb_db->te = 
			event_add_timed(ctdb->ev, ctdb_db, 
					timeval_current_ofs(ctdb->tunable.seqnum_frequency, 0),
					ctdb_ltdb_seqnum_check, ctdb_db);
	}

	tdb_enable_seqnum(ctdb_db->ltdb->tdb);
	ctdb_db->seqnum = tdb_get_seqnum(ctdb_db->ltdb->tdb);
	return 0;
}