Drivers¶
Tooz is provided with several drivers implementing the provided coordination API. While all drivers provides the same set of features with respect to the API, some of them have different properties.
Zookeeper¶
Driver: tooz.drivers.zookeeper.KazooDriver
Entrypoint name: zookeeper
or kazoo
Summary:
The zookeeper is the reference implementation and provides the most solid features as it’s possible to build a cluster of zookeeper servers that is resilient towards network partitions for example.
Test driver: tooz.drivers.zake.ZakeDriver
Test driver entrypoint name: zake
Considerations¶
- Primitives are based on sessions (and typically require careful selection of session heartbeat periodicity and server side configuration of session expiry).
Memcached¶
Driver: tooz.drivers.memcached.MemcachedDriver
Entrypoint name: memcached
Summary:
The memcached driver is a basic implementation and provides little resiliency, though it’s much simpler to setup. A lot of the features provided in tooz are based on timeout (heartbeats, locks, etc) so are less resilient than other backends.
Considerations¶
- Less resilient than other backends such as zookeeper and redis.
- Primitives are often based on TTL(s) that may expire before being renewed.
- Lacks certain primitives (compare and delete) so certain functionality is fragile and/or broken due to this.
Redis¶
Driver: tooz.drivers.redis.RedisDriver
Entrypoint name: redis
Summary:
The redis driver is a basic implementation and provides reasonable resiliency when used with redis-sentinel. A lot of the features provided in tooz are based on timeout (heartbeats, locks, etc) so are less resilient than other backends.
Considerations¶
- Less resilient than other backends such as zookeeper.
- Primitives are often based on TTL(s) that may expire before being renewed.
IPC¶
Driver: tooz.drivers.ipc.IPCDriver
Entrypoint name: ipc
Summary:
The IPC driver is based on Posix IPC API and implements a lock mechanism and some basic group primitives (with huge limitations).
Considerations¶
- The lock can only be distributed locally to a computer processes.
File¶
Driver: tooz.drivers.file.FileDriver
Entrypoint name: file
Summary:
The file driver is a simple driver based on files and directories. It implements a lock based on POSIX or Window file level locking mechanism and some basic group primitives (with huge limitations).
Considerations¶
- The lock can only be distributed locally to a computer processes.
- Certain concepts provided by it are not crash tolerant.
PostgreSQL¶
Driver: tooz.drivers.pgsql.PostgresDriver
Entrypoint name: postgresql
Summary:
The postgresql driver is a driver providing only a distributed lock (for now) and is based on the PostgreSQL database server and its API(s) that provide for advisory locks to be created and used by applications. When a lock is acquired it will release either when explicitly released or automatically when the database session ends (for example if the program using the lock crashes).
Considerations¶
- Lock that may be acquired restricted by
max_locks_per_transaction * (max_connections + max_prepared_transactions)
upper bound (PostgreSQL server configuration settings).
MySQL¶
Driver: tooz.drivers.mysql.MySQLDriver
Entrypoint name: mysql
Summary:
The MySQL driver is a driver providing only distributed locks (for now) and is based on the MySQL database server supported get_lock primitives. When a lock is acquired it will release either when explicitly released or automatically when the database session ends (for example if the program using the lock crashes).
Considerations¶
- Does not work correctly on some MySQL versions.
- Does not work when MySQL replicates from one server to another (locks are local to the server that they were created from).