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[324] make sure initial SQLite3 DB creation is exception safe.

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this is not really an issue of this task, and I believe we should soon stop
creating the schema in the accessor context in the first place, but the bug
is real so I fixed it anyway.  Assuming this creation code and the older
version of implementation will be gone soon, I simply duplicated the mostly
same code in both old and new implementations.

Also, it seemed extremely difficult (I'd say it's effectively impossible) to
test these cases.  I couldn't come up with any reasonable way to test them,
so I didn't add any test.
This commit is contained in:
JINMEI Tatuya
2012-04-02 11:07:50 -07:00
parent 16ad60fe0d
commit 4df83ec7d1
2 changed files with 93 additions and 34 deletions
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65
src/lib/datasrc/sqlite3_accessor.cc
View File

@@ -378,36 +378,67 @@ pair<int, int> checkSchemaVersion(sqlite3* db) {
}
}
// A helper class used in createDatabase() below so we manage the one shot
// transaction safely.
class ScopedTransaction {
public:
ScopedTransaction(sqlite3* db) : db_(NULL) {
// try for 5 secs (50*0.1)
for (size_t i = 0; i < 50; ++i) {
const int rc = sqlite3_exec(db, "BEGIN EXCLUSIVE TRANSACTION",
NULL, NULL, NULL);
if (rc == SQLITE_OK) {
break;
} else if (rc != SQLITE_BUSY || i == 50) {
isc_throw(SQLite3Error, "Unable to acquire exclusive lock "
"for database creation: " << sqlite3_errmsg(db));
}
doSleep();
}
// Hold the DB pointer once we have successfully acquired the lock.
db_ = db;
}
~ScopedTransaction() {
if (db_ != NULL) {
// Note: even rollback could fail in theory, but in that case
// we cannot do much for safe recovery anyway. We could at least
// log the event, but for now don't even bother to do that, with
// the expectation that we'll soon stop creating the schema in this
// module.
sqlite3_exec(db_, "ROLLBACK", NULL, NULL, NULL);
}
}
void commit() {
if (sqlite3_exec(db_, "COMMIT TRANSACTION", NULL, NULL, NULL) !=
SQLITE_OK) {
isc_throw(SQLite3Error, "Unable to commit newly created database "
"schema: " << sqlite3_errmsg(db_));
}
db_ = NULL;
}
private:
sqlite3* db_;
};
// return db version
pair<int, int>
createDatabase(sqlite3* db) {
logger.info(DATASRC_SQLITE_SETUP);
// try to get an exclusive lock. Once that is obtained, do the version
// check *again*, just in case this process was racing another
//
// try for 5 secs (50*0.1)
int rc;
logger.info(DATASRC_SQLITE_SETUP);
for (size_t i = 0; i < 50; ++i) {
rc = sqlite3_exec(db, "BEGIN EXCLUSIVE TRANSACTION", NULL, NULL,
NULL);
if (rc == SQLITE_OK) {
break;
} else if (rc != SQLITE_BUSY || i == 50) {
isc_throw(SQLite3Error, "Unable to acquire exclusive lock "
"for database creation: " << sqlite3_errmsg(db));
}
doSleep();
}
ScopedTransaction trasaction(db);
pair<int, int> schema_version = checkSchemaVersion(db);
if (schema_version.first == -1) {
for (int i = 0; SCHEMA_LIST[i] != NULL; ++i) {
if (sqlite3_exec(db, SCHEMA_LIST[i], NULL, NULL, NULL) !=
SQLITE_OK) {
isc_throw(SQLite3Error,
"Failed to set up schema " << SCHEMA_LIST[i]);
"Failed to set up schema " << SCHEMA_LIST[i]);
}
}
sqlite3_exec(db, "COMMIT TRANSACTION", NULL, NULL, NULL);
trasaction.commit();
// Return the version. We query again to ensure that the only point
// in which the current schema version is defined is in the create

62
src/lib/datasrc/sqlite3_datasrc.cc
View File

@@ -743,28 +743,56 @@ pair<int, int> check_schema_version(sqlite3* db) {
}
}
// A helper class used in create_database() below so we manage the one shot
// transaction safely.
class ScopedTransaction {
public:
ScopedTransaction(sqlite3* db) : db_(NULL) {
// try for 5 secs (50*0.1)
for (size_t i = 0; i < 50; ++i) {
const int rc = sqlite3_exec(db, "BEGIN EXCLUSIVE TRANSACTION",
NULL, NULL, NULL);
if (rc == SQLITE_OK) {
break;
} else if (rc != SQLITE_BUSY || i == 50) {
isc_throw(Sqlite3Error, "Unable to acquire exclusive lock "
"for database creation: " << sqlite3_errmsg(db));
}
do_sleep();
}
// Hold the DB pointer once we have successfully acquired the lock.
db_ = db;
}
~ScopedTransaction() {
if (db_ != NULL) {
// Note: even rollback could fail in theory, but in that case
// we cannot do much for safe recovery anyway. We could at least
// log the event, but for now don't even bother to do that, with
// the expectation that we'll soon stop creating the schema in this
// module.
sqlite3_exec(db_, "ROLLBACK", NULL, NULL, NULL);
}
}
void commit() {
if (sqlite3_exec(db_, "COMMIT TRANSACTION", NULL, NULL, NULL) !=
SQLITE_OK) {
isc_throw(Sqlite3Error, "Unable to commit newly created database "
"schema: " << sqlite3_errmsg(db_));
}
db_ = NULL;
}
private:
sqlite3* db_;
};
// return db version
pair<int, int> create_database(sqlite3* db) {
logger.info(DATASRC_SQLITE_SETUP);
// try to get an exclusive lock. Once that is obtained, do the version
// check *again*, just in case this process was racing another
//
// try for 5 secs (50*0.1)
int rc;
logger.info(DATASRC_SQLITE_SETUP);
for (size_t i = 0; i < 50; ++i) {
rc = sqlite3_exec(db, "BEGIN EXCLUSIVE TRANSACTION", NULL, NULL,
NULL);
if (rc == SQLITE_OK) {
break;
} else if (rc != SQLITE_BUSY || i == 50) {
isc_throw(Sqlite3Error, "Unable to acquire exclusive lock "
"for database creation: " << sqlite3_errmsg(db));
}
do_sleep();
}
ScopedTransaction transaction(db);
pair<int, int> schema_version = check_schema_version(db);
if (schema_version.first == -1) {
for (int i = 0; SCHEMA_LIST[i] != NULL; ++i) {
@@ -774,7 +802,7 @@ pair<int, int> create_database(sqlite3* db) {
"Failed to set up schema " << SCHEMA_LIST[i]);
}
}
sqlite3_exec(db, "COMMIT TRANSACTION", NULL, NULL, NULL);
transaction.commit();
// Return the version. We query again to ensure that the only point
// in which the current schema version is defined is in the