MemcachedLock

Distributed lock that is implemented based on Memcached’s caching service.

Implements: Lock, IConfigurable, IReferenceable, IOpenable

Description

The MemcachedLock class allows you to create a lock that is implemented based on the Memcached’s caching service.

Important points

  • The current implementation does not support authentication.

Configuration parameters

  • connection(s):
    • discovery_key: (optional) key to retrieve the connection from IDiscovery
    • host: host name or IP address
    • port: port number
    • uri: resource URI or connection string with all parameters in it
  • options:
    • max_size: maximum number of values stored in this cache (default: 1000)
    • max_key_size: maximum key length (default: 250)
    • max_expiration: maximum expiration duration in milliseconds (default: 2592000)
    • max_value: maximum value length (default: 1048576)
    • pool_size: pool size (default: 5)
    • reconnect: reconnection timeout in milliseconds (default: 10 sec)
    • retries: number of retries (default: 3)
    • timeout: default caching timeout in milliseconds (default: 1 minute)
    • failures: number of failures before stop retrying (default: 5)
    • retry: retry timeout in milliseconds (default: 30 sec)
    • idle: idle timeout before disconnect in milliseconds (default: 5 sec)

References

  • *:discovery:*:*:1.0 - (optional) IDiscovery services to resolve connection

Instance methods

close

Closes a component and frees used resources.

close(context: Optional[str])

  • context: IContext - (optional) a context to trace execution through a call chain.

configure

Configures a component by passing its configuration parameters.

configure(config: ConfigParams)

  • config: ConfigParams - configuration parameters to be set.

is_open

Checks if the component is open.

is_open(): bool

  • returns: bool - true if the component is open and false otherwise.

open

Opens the component.

open(context: Optional[IContext])

  • context: IContext - (optional) a context to trace execution through a call chain.

release_lock

Releases a prevously acquired lock by its key.

release_lock(context: Optional[IContext], key: str)

  • context: IContext - (optional) a context to trace execution through a call chainn.
  • key: str - unique lock key to release.

set_references

Sets references to dependent components.

set_references(references: IReferences)

  • references: IReferences - references to locate the component’s dependencies.

try_acquire_lock

Makes a single attempt to acquire a lock by its key. It returns immediately a positive or negative result.

try_acquire_lock(correlation_id: Optional[str], key: str, ttl: int): bool

  • correlation_id: Optional[str] - (optional) transaction id used to trace execution through the call chain.
  • key: str - unique lock key to acquire.
  • ttl: int - lock timeout (time to live) in milliseconds.
  • returns: bool - true if lock was successfull and false otherwise.

Examples

lock = MemcachedLock()
lock.configure(ConfigParams.from_tuples(
    "connection.host", "localhost",
    "connection.port", 11211
))
        
lock.open("123")
lock.acquire_lock("123", "key1", 3000, 1000)
try:
    # Processing...
    pass
finally:
    lock.release_lock("123", "key1")