source: branches/samba-3.2.x/source/lib/dbwrap_ctdb.c

/* 
   Unix SMB/CIFS implementation.
   Database interface wrapper around ctdbd
   Copyright (C) Volker Lendecke 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"
#ifdef CLUSTER_SUPPORT
#include "ctdb.h"
#include "ctdb_private.h"
#include "ctdbd_conn.h"

struct db_ctdb_ctx {
        struct tdb_wrap *wtdb;
        uint32 db_id;
};

struct db_ctdb_rec {
        struct db_ctdb_ctx *ctdb_ctx;
        struct ctdb_ltdb_header header;
};

static NTSTATUS db_ctdb_store(struct db_record *rec, TDB_DATA data, int flag)
{
        struct db_ctdb_rec *crec = talloc_get_type_abort(
                rec->private_data, struct db_ctdb_rec);
        TDB_DATA cdata;
        int ret;

        cdata.dsize = sizeof(crec->header) + data.dsize;

        if (!(cdata.dptr = SMB_MALLOC_ARRAY(uint8, cdata.dsize))) {
                return NT_STATUS_NO_MEMORY;
        }

        memcpy(cdata.dptr, &crec->header, sizeof(crec->header));
        memcpy(cdata.dptr + sizeof(crec->header), data.dptr, data.dsize);

        ret = tdb_store(crec->ctdb_ctx->wtdb->tdb, rec->key, cdata, TDB_REPLACE);

        SAFE_FREE(cdata.dptr);

        return (ret == 0) ? NT_STATUS_OK : NT_STATUS_INTERNAL_DB_CORRUPTION;
}


/* for persistent databases the store is a bit different. We have to
   ask the ctdb daemon to push the record to all nodes after the
   store */
static NTSTATUS db_ctdb_store_persistent(struct db_record *rec, TDB_DATA data, int flag)
{
        struct db_ctdb_rec *crec = talloc_get_type_abort(
                rec->private_data, struct db_ctdb_rec);
        TDB_DATA cdata;
        int ret;
        NTSTATUS status;

        cdata.dsize = sizeof(crec->header) + data.dsize;

        if (!(cdata.dptr = SMB_MALLOC_ARRAY(uint8, cdata.dsize))) {
                return NT_STATUS_NO_MEMORY;
        }

        crec->header.rsn++;

        memcpy(cdata.dptr, &crec->header, sizeof(crec->header));
        memcpy(cdata.dptr + sizeof(crec->header), data.dptr, data.dsize);

        ret = tdb_store(crec->ctdb_ctx->wtdb->tdb, rec->key, cdata, TDB_REPLACE);
        status = (ret == 0) ? NT_STATUS_OK : NT_STATUS_INTERNAL_DB_CORRUPTION;
        
        /* now tell ctdbd to update this record on all other nodes */
        if (NT_STATUS_IS_OK(status)) {
                status = ctdbd_persistent_store(messaging_ctdbd_connection(), crec->ctdb_ctx->db_id, rec->key, cdata);
        }

        SAFE_FREE(cdata.dptr);

        return status;
}

static NTSTATUS db_ctdb_delete(struct db_record *rec)
{
        struct db_ctdb_rec *crec = talloc_get_type_abort(
                rec->private_data, struct db_ctdb_rec);
        TDB_DATA data;
        int ret;

        /*
         * We have to store the header with empty data. TODO: Fix the
         * tdb-level cleanup
         */

        data.dptr = (uint8 *)&crec->header;
        data.dsize = sizeof(crec->header);

        ret = tdb_store(crec->ctdb_ctx->wtdb->tdb, rec->key, data, TDB_REPLACE);

        return (ret == 0) ? NT_STATUS_OK : NT_STATUS_INTERNAL_DB_CORRUPTION;
}

static int db_ctdb_record_destr(struct db_record* data)
{
        struct db_ctdb_rec *crec = talloc_get_type_abort(
                data->private_data, struct db_ctdb_rec);

        DEBUG(10, (DEBUGLEVEL > 10
                   ? "Unlocking db %u key %s\n"
                   : "Unlocking db %u key %.20s\n",
                   (int)crec->ctdb_ctx->db_id,
                   hex_encode(data, (unsigned char *)data->key.dptr,
                              data->key.dsize)));

        if (tdb_chainunlock(crec->ctdb_ctx->wtdb->tdb, data->key) != 0) {
                DEBUG(0, ("tdb_chainunlock failed\n"));
                return -1;
        }

        return 0;
}

static struct db_record *db_ctdb_fetch_locked(struct db_context *db,
                                              TALLOC_CTX *mem_ctx,
                                              TDB_DATA key)
{
        struct db_ctdb_ctx *ctx = talloc_get_type_abort(db->private_data,
                                                        struct db_ctdb_ctx);
        struct db_record *result;
        struct db_ctdb_rec *crec;
        NTSTATUS status;
        TDB_DATA ctdb_data;
        int migrate_attempts = 0;

        if (!(result = talloc(mem_ctx, struct db_record))) {
                DEBUG(0, ("talloc failed\n"));
                return NULL;
        }

        if (!(crec = TALLOC_ZERO_P(result, struct db_ctdb_rec))) {
                DEBUG(0, ("talloc failed\n"));
                TALLOC_FREE(result);
                return NULL;
        }

        result->private_data = (void *)crec;
        crec->ctdb_ctx = ctx;

        result->key.dsize = key.dsize;
        result->key.dptr = (uint8 *)talloc_memdup(result, key.dptr, key.dsize);
        if (result->key.dptr == NULL) {
                DEBUG(0, ("talloc failed\n"));
                TALLOC_FREE(result);
                return NULL;
        }

        /*
         * Do a blocking lock on the record
         */
again:

        if (DEBUGLEVEL >= 10) {
                char *keystr = hex_encode(result, key.dptr, key.dsize);
                DEBUG(10, (DEBUGLEVEL > 10
                           ? "Locking db %u key %s\n"
                           : "Locking db %u key %.20s\n",
                           (int)crec->ctdb_ctx->db_id, keystr));
                TALLOC_FREE(keystr);
        }
        
        if (tdb_chainlock(ctx->wtdb->tdb, key) != 0) {
                DEBUG(3, ("tdb_chainlock failed\n"));
                TALLOC_FREE(result);
                return NULL;
        }

        if (db->persistent) {
                result->store = db_ctdb_store_persistent;
        } else {
                result->store = db_ctdb_store;
        }
        result->delete_rec = db_ctdb_delete;
        talloc_set_destructor(result, db_ctdb_record_destr);

        ctdb_data = tdb_fetch(ctx->wtdb->tdb, key);

        /*
         * See if we have a valid record and we are the dmaster. If so, we can
         * take the shortcut and just return it.
         */

        if ((ctdb_data.dptr == NULL) ||
            (ctdb_data.dsize < sizeof(struct ctdb_ltdb_header)) ||
            ((struct ctdb_ltdb_header *)ctdb_data.dptr)->dmaster != get_my_vnn()
#if 0
            || (random() % 2 != 0)
#endif
) {
                SAFE_FREE(ctdb_data.dptr);
                tdb_chainunlock(ctx->wtdb->tdb, key);
                talloc_set_destructor(result, NULL);

                migrate_attempts += 1;

                DEBUG(10, ("ctdb_data.dptr = %p, dmaster = %u (%u)\n",
                           ctdb_data.dptr, ctdb_data.dptr ?
                           ((struct ctdb_ltdb_header *)ctdb_data.dptr)->dmaster : -1,
                           get_my_vnn()));

                status = ctdbd_migrate(messaging_ctdbd_connection(),ctx->db_id, key);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(5, ("ctdb_migrate failed: %s\n",
                                  nt_errstr(status)));
                        TALLOC_FREE(result);
                        return NULL;
                }
                /* now its migrated, try again */
                goto again;
        }

        if (migrate_attempts > 10) {
                DEBUG(0, ("db_ctdb_fetch_locked needed %d attempts\n",
                          migrate_attempts));
        }

        memcpy(&crec->header, ctdb_data.dptr, sizeof(crec->header));

        result->value.dsize = ctdb_data.dsize - sizeof(crec->header);
        result->value.dptr = NULL;

        if ((result->value.dsize != 0)
            && !(result->value.dptr = (uint8 *)talloc_memdup(
                         result, ctdb_data.dptr + sizeof(crec->header),
                         result->value.dsize))) {
                DEBUG(0, ("talloc failed\n"));
                TALLOC_FREE(result);
        }

        SAFE_FREE(ctdb_data.dptr);

        return result;
}

/*
  fetch (unlocked, no migration) operation on ctdb
 */
static int db_ctdb_fetch(struct db_context *db, TALLOC_CTX *mem_ctx,
                         TDB_DATA key, TDB_DATA *data)
{
        struct db_ctdb_ctx *ctx = talloc_get_type_abort(db->private_data,
                                                        struct db_ctdb_ctx);
        NTSTATUS status;
        TDB_DATA ctdb_data;

        /* try a direct fetch */
        ctdb_data = tdb_fetch(ctx->wtdb->tdb, key);

        /*
         * See if we have a valid record and we are the dmaster. If so, we can
         * take the shortcut and just return it.
         * we bypass the dmaster check for persistent databases
         */
        if ((ctdb_data.dptr != NULL) &&
            (ctdb_data.dsize >= sizeof(struct ctdb_ltdb_header)) &&
            (db->persistent ||
             ((struct ctdb_ltdb_header *)ctdb_data.dptr)->dmaster == get_my_vnn())) {
                /* we are the dmaster - avoid the ctdb protocol op */

                data->dsize = ctdb_data.dsize - sizeof(struct ctdb_ltdb_header);
                if (data->dsize == 0) {
                        SAFE_FREE(ctdb_data.dptr);
                        data->dptr = NULL;
                        return 0;
                }

                data->dptr = (uint8 *)talloc_memdup(
                        mem_ctx, ctdb_data.dptr+sizeof(struct ctdb_ltdb_header),
                        data->dsize);

                SAFE_FREE(ctdb_data.dptr);

                if (data->dptr == NULL) {
                        return -1;
                }
                return 0;
        }

        SAFE_FREE(ctdb_data.dptr);

        /* we weren't able to get it locally - ask ctdb to fetch it for us */
        status = ctdbd_fetch(messaging_ctdbd_connection(),ctx->db_id, key, mem_ctx, data);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(5, ("ctdbd_fetch failed: %s\n", nt_errstr(status)));
                return -1;
        }

        return 0;
}

struct traverse_state {
        struct db_context *db;
        int (*fn)(struct db_record *rec, void *private_data);
        void *private_data;
};

static void traverse_callback(TDB_DATA key, TDB_DATA data, void *private_data)
{
        struct traverse_state *state = (struct traverse_state *)private_data;
        struct db_record *rec;
        TALLOC_CTX *tmp_ctx = talloc_new(state->db);
        /* we have to give them a locked record to prevent races */
        rec = db_ctdb_fetch_locked(state->db, tmp_ctx, key);
        if (rec && rec->value.dsize > 0) {
                state->fn(rec, state->private_data);
        }
        talloc_free(tmp_ctx);
}

static int traverse_persistent_callback(TDB_CONTEXT *tdb, TDB_DATA kbuf, TDB_DATA dbuf,
                                        void *private_data)
{
        struct traverse_state *state = (struct traverse_state *)private_data;
        struct db_record *rec;
        TALLOC_CTX *tmp_ctx = talloc_new(state->db);
        int ret = 0;
        /* we have to give them a locked record to prevent races */
        rec = db_ctdb_fetch_locked(state->db, tmp_ctx, kbuf);
        if (rec && rec->value.dsize > 0) {
                ret = state->fn(rec, state->private_data);
        }
        talloc_free(tmp_ctx);
        return ret;
}

static int db_ctdb_traverse(struct db_context *db,
                            int (*fn)(struct db_record *rec,
                                      void *private_data),
                            void *private_data)
{
        struct db_ctdb_ctx *ctx = talloc_get_type_abort(db->private_data,
                                                        struct db_ctdb_ctx);
        struct traverse_state state;

        state.db = db;
        state.fn = fn;
        state.private_data = private_data;

        if (db->persistent) {
                /* for persistent databases we don't need to do a ctdb traverse,
                   we can do a faster local traverse */
                return tdb_traverse(ctx->wtdb->tdb, traverse_persistent_callback, &state);
        }


        ctdbd_traverse(ctx->db_id, traverse_callback, &state);
        return 0;
}

static NTSTATUS db_ctdb_store_deny(struct db_record *rec, TDB_DATA data, int flag)
{
        return NT_STATUS_MEDIA_WRITE_PROTECTED;
}

static NTSTATUS db_ctdb_delete_deny(struct db_record *rec)
{
        return NT_STATUS_MEDIA_WRITE_PROTECTED;
}

static void traverse_read_callback(TDB_DATA key, TDB_DATA data, void *private_data)
{
        struct traverse_state *state = (struct traverse_state *)private_data;
        struct db_record rec;
        rec.key = key;
        rec.value = data;
        rec.store = db_ctdb_store_deny;
        rec.delete_rec = db_ctdb_delete_deny;
        rec.private_data = state->db;
        state->fn(&rec, state->private_data);
}

static int traverse_persistent_callback_read(TDB_CONTEXT *tdb, TDB_DATA kbuf, TDB_DATA dbuf,
                                        void *private_data)
{
        struct traverse_state *state = (struct traverse_state *)private_data;
        struct db_record rec;
        rec.key = kbuf;
        rec.value = dbuf;
        rec.store = db_ctdb_store_deny;
        rec.delete_rec = db_ctdb_delete_deny;
        rec.private_data = state->db;

        if (rec.value.dsize <= sizeof(struct ctdb_ltdb_header)) {
                /* a deleted record */
                return 0;
        }
        rec.value.dsize -= sizeof(struct ctdb_ltdb_header);
        rec.value.dptr += sizeof(struct ctdb_ltdb_header);

        return state->fn(&rec, state->private_data);
}

static int db_ctdb_traverse_read(struct db_context *db,
                                 int (*fn)(struct db_record *rec,
                                           void *private_data),
                                 void *private_data)
{
        struct db_ctdb_ctx *ctx = talloc_get_type_abort(db->private_data,
                                                        struct db_ctdb_ctx);
        struct traverse_state state;

        state.db = db;
        state.fn = fn;
        state.private_data = private_data;

        if (db->persistent) {
                /* for persistent databases we don't need to do a ctdb traverse,
                   we can do a faster local traverse */
                return tdb_traverse_read(ctx->wtdb->tdb, traverse_persistent_callback_read, &state);
        }

        ctdbd_traverse(ctx->db_id, traverse_read_callback, &state);
        return 0;
}

static int db_ctdb_get_seqnum(struct db_context *db)
{
        struct db_ctdb_ctx *ctx = talloc_get_type_abort(db->private_data,
                                                        struct db_ctdb_ctx);
        return tdb_get_seqnum(ctx->wtdb->tdb);
}

static int db_ctdb_trans_dummy(struct db_context *db)
{
        /*
         * Not implemented yet, just return ok
         */
        return 0;
}

struct db_context *db_open_ctdb(TALLOC_CTX *mem_ctx,
                                const char *name,
                                int hash_size, int tdb_flags,
                                int open_flags, mode_t mode)
{
        struct db_context *result;
        struct db_ctdb_ctx *db_ctdb;
        char *db_path;

        if (!lp_clustering()) {
                DEBUG(10, ("Clustering disabled -- no ctdb\n"));
                return NULL;
        }

        if (!(result = TALLOC_ZERO_P(mem_ctx, struct db_context))) {
                DEBUG(0, ("talloc failed\n"));
                TALLOC_FREE(result);
                return NULL;
        }

        if (!(db_ctdb = TALLOC_P(result, struct db_ctdb_ctx))) {
                DEBUG(0, ("talloc failed\n"));
                TALLOC_FREE(result);
                return NULL;
        }

        if (!NT_STATUS_IS_OK(ctdbd_db_attach(messaging_ctdbd_connection(),name, &db_ctdb->db_id, tdb_flags))) {
                DEBUG(0, ("ctdbd_db_attach failed for %s\n", name));
                TALLOC_FREE(result);
                return NULL;
        }

        db_path = ctdbd_dbpath(messaging_ctdbd_connection(), db_ctdb, db_ctdb->db_id);

        result->persistent = ((tdb_flags & TDB_CLEAR_IF_FIRST) == 0);

        /* only pass through specific flags */
        tdb_flags &= TDB_SEQNUM;

        /* honor permissions if user has specified O_CREAT */
        if (open_flags & O_CREAT) {
                chmod(db_path, mode);
        }

        db_ctdb->wtdb = tdb_wrap_open(db_ctdb, db_path, hash_size, tdb_flags, O_RDWR, 0);
        if (db_ctdb->wtdb == NULL) {
                DEBUG(0, ("Could not open tdb %s: %s\n", db_path, strerror(errno)));
                TALLOC_FREE(result);
                return NULL;
        }
        talloc_free(db_path);

        result->private_data = (void *)db_ctdb;
        result->fetch_locked = db_ctdb_fetch_locked;
        result->fetch = db_ctdb_fetch;
        result->traverse = db_ctdb_traverse;
        result->traverse_read = db_ctdb_traverse_read;
        result->get_seqnum = db_ctdb_get_seqnum;
        result->transaction_start = db_ctdb_trans_dummy;
        result->transaction_commit = db_ctdb_trans_dummy;
        result->transaction_cancel = db_ctdb_trans_dummy;

        DEBUG(3,("db_open_ctdb: opened database '%s' with dbid 0x%x\n",
                 name, db_ctdb->db_id));

        return result;
}
#endif