/* ------------------------------------------------------------------- * * bdberl: Berkeley DB Driver for Erlang * Copyright (c) 2008 The Hive. All rights reserved. * * ------------------------------------------------------------------- */ #include #include #include #include #include "hive_hash.h" #include "bdberl_drv.h" #include "bin_helper.h" /** * Function prototypes */ static int open_database(const char* name, DBTYPE type, unsigned flags, PortData* data, int* errno); static int close_database(int dbref, unsigned flags, PortData* data); static void do_async_put(void* arg); static void do_async_put_free(void* arg); static void do_async_get(void* arg); static void do_async_get_free(void* arg); static void do_async_txnop(void* arg); static int add_dbref(PortData* data, int dbref); static int del_dbref(PortData* data, int dbref); static int has_dbref(PortData* data, int dbref); static int add_portref(int dbref, ErlDrvPort port); static int del_portref(int dbref, ErlDrvPort port); static int alloc_dbref(); static void* zalloc(unsigned int size); /** * Global instance of DB_ENV; only a single one exists per O/S process. */ static DB_ENV* G_DB_ENV; /** * Global variable to track the return code from opening the DB_ENV. We track this * value so as to provide a useful error code when the user attempts to open the * port and it fails due to an error that occurred when opening the environment. */ static int G_DB_ENV_ERROR; /** * G_DATABASES is a global array of Database structs. Used to track currently opened DB* * handles and ensure that they get cleaned up when all ports which were using them exit or * explicitly close them. * * This array is allocated when the driver is first initialized and does not grow/shrink * dynamically. G_DATABASES_SIZE contains the size of the array. G_DATABASES_NAMES is a hash of * filenames to array index for an opened Database. * * All access to G_DATABASES and G_DATABASES_NAMES must be protected by the read/write lock * G_DATABASES_RWLOCK. */ static Database* G_DATABASES; static int G_DATABASES_SIZE; static ErlDrvRWLock* G_DATABASES_RWLOCK; static hive_hash* G_DATABASES_NAMES; /** * Helpful macros */ #define READ_LOCK(L) erl_drv_rwlock_rlock(L) #define READ_UNLOCK(L) erl_drv_rwlock_runlock(L) #define PROMOTE_READ_LOCK(L) { erl_drv_rwlock_runlock(L); erl_drv_rwlock_rwlock(L); } #define WRITE_LOCK(L) erl_drv_rwlock_rwlock(L) #define WRITE_UNLOCK(L) erl_drv_rwlock_rwunlock(L) #define UNPACK_BYTE(_buf, _off) (_buf[_off]) #define UNPACK_INT(_buf, _off) *((int*)(_buf+(_off))) #define UNPACK_STRING(_buf, _off) (char*)(_buf+(_off)) #define UNPACK_BLOB(_buf, _off) (void*)(_buf+(_off)) #define RETURN_BH(bh, outbuf) *outbuf = (char*)bh.bin; return bh.bin->orig_size; #define RETURN_INT(val, outbuf) { \ BinHelper bh; \ bin_helper_init(&bh, 4); \ bin_helper_push_int32(&bh, val); \ RETURN_BH(bh, outbuf); } DRIVER_INIT(bdberl_drv) { printf("DRIVER INIT\n"); // Setup flags we'll use to init the environment int flags = DB_INIT_LOCK | /* Enable support for locking */ DB_INIT_TXN | /* Enable support for transactions */ DB_INIT_MPOOL | /* Enable support for memory pools */ DB_RECOVER | /* Enable support for recovering from failures */ DB_CREATE | /* Create files as necessary */ DB_REGISTER | /* Run recovery if needed */ DB_THREAD; /* Make the environment free-threaded */ // Initialize global environment -- use environment variable DB_HOME to // specify where the working directory is db_env_create(&G_DB_ENV, 0); G_DB_ENV_ERROR = G_DB_ENV->open(G_DB_ENV, 0, flags, 0); if (G_DB_ENV_ERROR == 0) { // Use the BDBERL_MAX_DBS environment value to determine the max # of // databases to permit the VM to open at once. Defaults to 1024. G_DATABASES_SIZE = 1024; char* max_dbs_str = getenv("BDBERL_MAX_DBS"); /* TODO: Use erl_drv_getenv */ if (max_dbs_str != 0) { G_DATABASES_SIZE = atoi(max_dbs_str); if (G_DATABASES_SIZE <= 0) { G_DATABASES_SIZE = 1024; } } // Make sure we can distiguish between lock timeouts and deadlocks G_DB_ENV->set_flags(G_DB_ENV, DB_TIME_NOTGRANTED, 1); // BDB is setup -- allocate structures for tracking databases G_DATABASES = (Database*) driver_alloc(sizeof(Database) * G_DATABASES_SIZE); memset(G_DATABASES, '\0', sizeof(Database) * G_DATABASES_SIZE); G_DATABASES_RWLOCK = erl_drv_rwlock_create("bdberl_drv: G_DATABASES_RWLOCK"); G_DATABASES_NAMES = hive_hash_new(G_DATABASES_SIZE); } else { // Something bad happened while initializing BDB; in this situation we // cleanup and set the environment to zero. Attempts to open ports will // fail and the user will have to sort out how to resolve the issue. G_DB_ENV->close(G_DB_ENV, 0); G_DB_ENV = 0; } return &bdberl_drv_entry; } static ErlDrvData bdberl_drv_start(ErlDrvPort port, char* buffer) { // Make sure we have a functional environment -- if we don't, // bail... if (!G_DB_ENV) { return ERL_DRV_ERROR_BADARG; } PortData* d = (PortData*)driver_alloc(sizeof(PortData)); memset(d, '\0', sizeof(PortData)); // Save handle to the port d->port = port; // Make sure port is running in binary mode set_port_control_flags(port, PORT_CONTROL_FLAG_BINARY); return (ErlDrvData)d; } static void bdberl_drv_stop(ErlDrvData handle) { PortData* d = (PortData*)handle; // TODO: Investigate if we need to worry about queued up async operations. It seems like the VM // SHOULD ensure the port doesn't disappear while something is in the queue... // If a txn is currently active, terminate it. We _must_ do it synchronously (unfortunately) as // there doesn't seem to be a to do an async op while stopping the driver. if (d->txn) { d->txn->abort(d->txn); } // Close all the databases we previously opened while (d->dbrefs) { close_database(d->dbrefs->dbref, 0, d); } // Release the port instance data driver_free(handle); } static void bdberl_drv_finish() { // Driver is unloading -- cleanup and shut down the BDB environment. Note that we assume // all ports have been released and thuse all databases/txns/etc are also gone. G_DB_ENV->close(G_DB_ENV, 0); driver_free(G_DATABASES); erl_drv_rwlock_destroy(G_DATABASES_RWLOCK); hive_hash_destroy(G_DATABASES_NAMES); } static int bdberl_drv_control(ErlDrvData handle, unsigned int cmd, char* inbuf, int inbuf_sz, char** outbuf, int outbuf_sz) { PortData* d = (PortData*)handle; switch(cmd) { case CMD_OPEN_DB: { // Extract the type code and filename from the inbuf // Inbuf is: <> unsigned flags = (unsigned) UNPACK_INT(inbuf, 0); DBTYPE type = (DBTYPE) UNPACK_BYTE(inbuf, 4); char* name = UNPACK_STRING(inbuf, 5); int dbref; int status; int rc = open_database(name, type, flags, d, &dbref); if (rc == 0) { status = STATUS_OK; } else { status = STATUS_ERROR; dbref = rc; } // Pack the status and dbref (or errno) into a binary and return it // Outbuf is: <> BinHelper bh; bin_helper_init(&bh, 5); bin_helper_push_byte(&bh, status); bin_helper_push_int32(&bh, dbref); RETURN_BH(bh, outbuf); } case CMD_CLOSE_DB: { // TODO: If data is inflight, fail. Abort any open txns. // Take the provided dbref and attempt to close it // Inbuf is: <> int dbref = UNPACK_INT(inbuf, 0); unsigned flags = (unsigned) UNPACK_INT(inbuf, 4); int rc = close_database(dbref, flags, d); // Outbuf is: <> RETURN_INT(rc, outbuf); } case CMD_TXN_BEGIN: { // If an async operaiton is pending, fail if (d->async_op != CMD_NONE) { RETURN_INT(ERROR_ASYNC_PENDING, outbuf); } // If we already have a txn open, fail if (d->txn != 0) { RETURN_INT(ERROR_TXN_OPEN, outbuf); } // Outbuf is <> int rc = G_DB_ENV->txn_begin(G_DB_ENV, 0, &(d->txn), 0); RETURN_INT(rc, outbuf); } case CMD_TXN_COMMIT: case CMD_TXN_ABORT: { // If an async operation is pending, fail if (d->async_op != CMD_NONE) { RETURN_INT(ERROR_ASYNC_PENDING, outbuf); } // If we don't already have a txn open, fail if (d->txn == 0) { RETURN_INT(ERROR_NO_TXN, outbuf); } // Allocate operation structure AsyncData* adata = zalloc(sizeof(AsyncData)); adata->port = d; // Update port data to indicate we have an operation in progress d->async_op = cmd; // Schedule async operation to execute the commit/abort unsigned int key = (unsigned int)d->port; driver_async(d->port, &key, &do_async_txnop, adata, 0); // Outbuf is <> RETURN_INT(0, outbuf); } case CMD_PUT: case CMD_GET: { // If another async op is pending, fail if (d->async_op != CMD_NONE) { RETURN_INT(ERROR_ASYNC_PENDING, outbuf); } // Inbuf is: << DbRef:32, Rest/binary>> int dbref = UNPACK_INT(inbuf, 0); // Make sure this port currently has dbref open -- if it doesn't, error out. Of note, // if it's in our list, we don't need to grab the RWLOCK, as we don't have to worry about // the underlying handle disappearing since we have a reference. if (has_dbref(d, dbref)) { // Allocate operation structure void* thread_data = zalloc(sizeof(AsyncData) + inbuf_sz); AsyncData* adata = (AsyncData*)thread_data; adata->port = d; adata->db = G_DATABASES[dbref].db; adata->payload = thread_data + sizeof(AsyncData); // Copy the payload into place memcpy(adata->payload, inbuf, inbuf_sz); // Mark the port as busy and then schedule the appropriate async operation d->async_op = cmd; unsigned int key = (unsigned int)d->port; if (cmd == CMD_PUT) { driver_async(d->port, &key, &do_async_put, thread_data, &do_async_put_free); } else if (cmd == CMD_GET) { driver_async(d->port, &key, &do_async_get, thread_data, &do_async_get_free); } // Let caller know that the operation is in progress // Outbuf is: <<0:32>> RETURN_INT(0, outbuf); } else { // Invalid dbref RETURN_INT(ERROR_INVALID_DBREF, outbuf); } } } *outbuf = 0; return 0; } static void bdberl_drv_ready_async(ErlDrvData handle, ErlDrvThreadData thread_data) { // TODO: If GET/PUT fails due to DEADLOCK, detect and cleanup txn pointer accordingly printf("ready_async\n"); PortData* d = (PortData*)handle; switch (d->async_op) { case CMD_PUT: case CMD_TXN_COMMIT: case CMD_TXN_ABORT: { // Extract return code == if it's zero, send back "ok" to driver process; otherwise // send a {error, Reason} tuple AsyncData* adata = (AsyncData*)thread_data; if (adata->rc == 0) { ErlDrvTermData response[] = { ERL_DRV_ATOM, driver_mk_atom("ok") }; driver_output_term(d->port, response, sizeof(response) / sizeof(response[0])); } else { ErlDrvTermData response[] = { ERL_DRV_ATOM, driver_mk_atom("error"), ERL_DRV_INT, adata->rc, ERL_DRV_TUPLE, 2}; driver_output_term(d->port, response, sizeof(response) / sizeof(response[0])); } // If this was a commit/abort, clear out the txn handle if (d->async_op == CMD_TXN_COMMIT || d->async_op == CMD_TXN_ABORT) { d->txn = 0; } // Cleanup async data and mark the port as not busy driver_free(adata); d->async_op = CMD_NONE; break; } case CMD_GET: { // Extract return code == if it's zero, send back {ok, Payload} or not_found to driver // process; otherwise send a {error, Reason} tuple AsyncData* adata = (AsyncData*)thread_data; if (adata->rc == 0) { ErlDrvTermData response[] = { ERL_DRV_ATOM, driver_mk_atom("ok"), ERL_DRV_BUF2BINARY, (ErlDrvTermData)adata->payload, (ErlDrvUInt)adata->payload_sz, ERL_DRV_TUPLE, 2}; driver_output_term(d->port, response, sizeof(response) / sizeof(response[0])); } else if (adata->rc == DB_NOTFOUND) { printf("not found\n"); ErlDrvTermData response[] = { ERL_DRV_ATOM, driver_mk_atom("not_found") }; driver_output_term(d->port, response, sizeof(response) / sizeof(response[0])); } else { ErlDrvTermData response[] = { ERL_DRV_ATOM, driver_mk_atom("error"), ERL_DRV_INT, adata->rc, ERL_DRV_TUPLE, 2}; driver_output_term(d->port, response, sizeof(response) / sizeof(response[0])); } // Cleanup async data and mark the port as not busy driver_free(adata->payload); driver_free(adata); d->async_op = CMD_NONE; break; } } } static void bdberl_drv_process_exit(ErlDrvData handle, ErlDrvMonitor *monitor) { } static int open_database(const char* name, DBTYPE type, unsigned int flags, PortData* data, int* dbref_res) { *dbref_res = -1; READ_LOCK(G_DATABASES_RWLOCK); // Look up the database by name in our hash table Database* database = (Database*)hive_hash_get(G_DATABASES_NAMES, name); if (database) { // Convert the database pointer into a dbref int dbref = database - G_DATABASES; // Great, the database was previously opened by someone else. Add it to our // list of refs, and if it's a new addition also register this port with the // Database structure in G_DATABASES if (add_dbref(data, dbref)) { // Need to update G_DATABASES -- grab the write lock PROMOTE_READ_LOCK(G_DATABASES_RWLOCK); // Add a reference to this port add_portref(dbref, data->port); // Release RW lock and return the ref WRITE_UNLOCK(G_DATABASES_RWLOCK); *dbref_res = dbref; return 0; } else { // Already in our list of opened databases -- unlock and return the reference READ_UNLOCK(G_DATABASES_RWLOCK); *dbref_res = dbref; return 0; } } else { // This database hasn't been opened yet -- grab a write lock PROMOTE_READ_LOCK(G_DATABASES_RWLOCK); // While waiting on the write lock, another thread could have slipped in and // opened the database, so do one more check to see if the database is already // open database = (Database*)hive_hash_get(G_DATABASES_NAMES, name); if (database) { // Database got created while we were waiting on the write lock, add a reference // to our port and drop the lock ASAP int dbref = database - G_DATABASES; add_portref(dbref, data->port); WRITE_UNLOCK(G_DATABASES_RWLOCK); add_dbref(data, dbref); *dbref_res = dbref; return 0; } // Database hasn't been created while we were waiting on write lock, so // create/open it // Find the first available slot in G_DATABASES; the index will be our // reference for database operations int dbref = alloc_dbref(); if (dbref < 0) { // No more slots available WRITE_UNLOCK(G_DATABASES_RWLOCK); return ERROR_MAX_DBS; } // Create the DB handle DB* db; int rc = db_create(&db, G_DB_ENV, 0); if (rc != 0) { // Failure while creating the database handle -- drop our lock and return // the code WRITE_UNLOCK(G_DATABASES_RWLOCK); return rc; } // Attempt to open our database rc = db->open(db, 0, name, 0, type, flags, 0); if (rc != 0) { // Failure while opening the database -- cleanup the handle, drop the lock // and return db->close(db, 0); WRITE_UNLOCK(G_DATABASES_RWLOCK); return rc; } // Database is open. Store all the data into the allocated ref G_DATABASES[dbref].db = db; G_DATABASES[dbref].name = strdup(name); G_DATABASES[dbref].ports = zalloc(sizeof(PortList)); G_DATABASES[dbref].ports->port = data->port; // Make entry in hash table of names hive_hash_add(G_DATABASES_NAMES, G_DATABASES[dbref].name, &(G_DATABASES[dbref])); // Drop the write lock WRITE_UNLOCK(G_DATABASES_RWLOCK); // Add the dbref to the port list add_dbref(data, dbref); *dbref_res = dbref; return 0; } } static int close_database(int dbref, unsigned flags, PortData* data) { printf("Closing %d for port %p\n", dbref, data->port); // Remove this database from our list if (del_dbref(data, dbref)) { // Something was actually deleted from our list -- now we need to disassociate the // calling port with the global database structure. WRITE_LOCK(G_DATABASES_RWLOCK); assert(G_DATABASES[dbref].db != 0); assert(G_DATABASES[dbref].ports != 0); // Now disassociate this port from the database's port list del_portref(dbref, data->port); // Finally, if there are no other references to the database, close out // the database completely Database* database = &G_DATABASES[dbref]; if (database->ports == 0) { printf("Closing actual database for dbref %d\n", dbref); // Close out the BDB handle database->db->close(database->db, flags); // Remove the entry from the names map hive_hash_remove(G_DATABASES_NAMES, database->name); free((char*)database->name); // Zero out the whole record memset(database, '\0', sizeof(Database)); } WRITE_UNLOCK(G_DATABASES_RWLOCK); return 1; } return 0; } static void do_async_put(void* arg) { printf("do_async_put\n"); // Payload is: <> AsyncData* adata = (AsyncData*)arg; unsigned flags = UNPACK_INT(adata->payload, 4); // Setup DBTs DBT key; DBT value; memset(&key, '\0', sizeof(DBT)); memset(&value, '\0', sizeof(DBT)); // Parse payload into DBTs key.size = UNPACK_INT(adata->payload, 8); key.data = UNPACK_BLOB(adata->payload, 12); value.size = UNPACK_INT(adata->payload, 12 + key.size); value.data = UNPACK_BLOB(adata->payload, 12 + key.size + 4); // Execute the actual put -- we'll process the result back in the driver_async_ready function // All databases are opened with AUTO_COMMIT, so if msg->port->txn is NULL, the put will still // be atomic adata->rc = adata->db->put(adata->db, adata->port->txn, &key, &value, flags); } static void do_async_put_free(void* arg) { printf("do_async_put_free\n"); } static void do_async_get(void* arg) { printf("do_async_get\n"); AsyncData* adata = (AsyncData*)arg; // Setup DBTs DBT key; DBT value; memset(&key, '\0', sizeof(DBT)); memset(&value, '\0', sizeof(DBT)); // Parse payload into DBT // Payload is: << DbRef:32, KeyLen:32, Key:KeyLen >> key.size = *((int*)(adata->payload + 4)); key.data = (void*)(adata->payload + 8); // Allocate memory to hold the value -- hard code initial size to 4k // TODO: Make this smarter! value.data = zalloc(4096); value.ulen = 4096; value.flags = DB_DBT_USERMEM; int rc = adata->db->get(adata->db, adata->port->txn, &key, &value, 0); while (rc == DB_BUFFER_SMALL) { // Grow our value buffer and try again value.data = driver_realloc(value.data, value.size); value.ulen = value.size; rc = adata->db->get(adata->db, adata->port->txn, &key, &value, 0); } adata->payload = value.data; adata->payload_sz = value.size; // Not ulen -- we want the actual data size adata->rc = rc; } static void do_async_get_free(void* arg) { printf("do_async_get_free\n"); } static void do_async_txnop(void* arg) { printf("do_async_txnop\n"); // Execute the actual commit/abort AsyncData* adata = (AsyncData*)arg; if (adata->port->async_op == CMD_TXN_COMMIT) { adata->rc = adata->port->txn->commit(adata->port->txn, 0); } else { adata->rc = adata->port->txn->abort(adata->port->txn); } } static void* zalloc(unsigned int size) { void* res = driver_alloc(size); memset(res, '\0', size); return res; } #define zfree(p) driver_free(p) static int add_portref(int dbref, ErlDrvPort port) { PortList* current = G_DATABASES[dbref].ports; if (current) { PortList* last = 0; do { // If the current item matches our port, bail -- nothing to do here if (current->port == port) { return 0; } last = current; current = current->next; } while (current != 0); // At the end of the list -- allocate a new entry for this por current = (PortList*)zalloc(sizeof(PortList)); current->port = port; last->next = current; return 1; } else { // Current was initially NULL, so alloc the first one and add it. current = zalloc(sizeof(PortList)); current->port = port; G_DATABASES[dbref].ports = current; return 1; } } static int del_portref(int dbref, ErlDrvPort port) { PortList* current = G_DATABASES[dbref].ports; PortList* last = 0; while (current) { if (current->port == port) { // Found our match -- look back and connect the last item to our next if (last) { last->next = current->next; } else { G_DATABASES[dbref].ports = current->next; } // Delete this entry zfree(current); return 1; } last = current; current = current->next; } // Didn't delete anything return 0; } /** * Add a db reference to a port's DbRefList. Returns 1 if added; 0 if already present */ static int add_dbref(PortData* data, int dbref) { DbRefList* current = data->dbrefs; if (current) { DbRefList* last = 0; do { if (current->dbref == dbref) { return 0; } last = current; current = current->next; } while (current != 0); // At the end of the list -- allocate a new entry current = zalloc(sizeof(DbRefList)); current->dbref = dbref; last->next = current; return 1; } else { // Current was initially NULL, so alloc the first one current = zalloc(sizeof(DbRefList)); current->dbref = dbref; data->dbrefs = current; return 1; } } /** * Delete a db reference from a port's DbRefList. Returns 1 if deleted; 0 if not */ static int del_dbref(PortData* data, int dbref) { DbRefList* current = data->dbrefs; DbRefList* last = 0; while (current) { if (current->dbref == dbref) { // Found our match -- look back and connect the last item to our next if (last) { last->next = current->next; } else { data->dbrefs = current->next; } // Delete this entry zfree(current); return 1; } last = current; current = current->next; } // Didn't delete anything return 0; } /** * Validate that a provided dbref is currently opened by a port. Return 1 if true; 0 if false. */ static int has_dbref(PortData* data, int dbref) { DbRefList* current = data->dbrefs; while (current) { if (current->dbref == dbref) { return 1; } current = current->next; } return 0; } /** * Allocate a Database structure; find first available slot in G_DATABASES and return the * index of it. If no free slots are available, return -1 */ static int alloc_dbref() { int i; for (i = 0; i < G_DATABASES_SIZE; i++) { if (G_DATABASES[i].db == 0) { return i; } } return -1; }