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PSLX provides a set of tools to assist development, and they include

  1. LRU cache for caching.
  2. SQL tool for connecting to SQL database and executing queries.
  3. Mongodb tool for connection to mongodb.
  4. Fetcher tool to fetch partitioned ProtoTable (whose values are of the same proto message type and keys are timestamps).
  5. Watcher tool to fetch partitioned ProtoTable (whose values are of the same proto message type and keys are timestamps).
  6. Registry tool to be used as decorators to register functions.

Documentation for LRU Caching

LRU caching supports the following methods:

__init__(max_capacity)
  • Description: create a LRU cache with capacity equal max_capacity.
  • Arguments:
    1. max_capacity: the maximum capacity of the LRU cache.
get(key)
  • Description: get the value stored in the key in the LRU cache.
  • Arguments:
    1. key: the key of the value. If key is not found, the function will return None.
  • Return: the value corresponding to the key.
set(key, value)
  • Description: set the key value pair to the cache.
  • Arguments:
    1. key: the key of the pair to be inserted.
    2. value: the value of the pair to be inserted.

Documentation for SQL Tool

SQL tool supports the following methods:

__init__()
  • Description: create an instance of the SQL tool.
connect_to_database(credential, database)
  • Description: connect to the database name with credential.
  • Arguments:
    1. credential: the credential used to connect to the database.
    2. database: the name of the database that is going to be connected to.
execute_query_str(query_str, modification)
  • Description: execute the query string.
  • Arguments:
    1. query_str: the string of the query to be executed.
    2. modification: boolean indicating whether the query will modify the database.
execute_query_file(query_file, modification)
  • Description: execute the query contained in a file.
  • Arguments:
    1. query_file: the file that contains the query.
    2. modification: boolean indicating whether the query will modify the database.

Note that before executing any queries, please connect to a database first.

Documentation for Mongodb Tool

Mongodb tool supports the following methods:

__init__()
  • Description: create an instance of the Mongodb tool.
connect_to_database(credential)
  • Description: connect to mongodb with credential.
  • Arguments:
    1. credential: the credential used to the connect to mongodb.
list_databases()
  • Description: list all the database names.
list_collections(database_name)
  • Description: list the collection names in the database.
  • Arguments:
    1. database_name: the name of the database.
get_database(database_name)
  • Decription: get the database with database name.
  • Arguments:
    1. database_name: the name of the database.
get_collection(database_name, collection_name)
  • Decription: get the collection with collection name in a database.
  • Arguments:
    1. database_name: the name of the database.
    2. collection_name: the name of the collection.

Documentation for Fetcher Tool

Tool to fetch the latest, oldest data or data within a time range.

To initialize PartitionerFetcher

__init__(partitioner, logger)
  • Description: initialize a PartitionerFetcher
  • Arguments:
    1. partitioner: the partitioner object to fetch. It needs to have underlying storage of a ProtoTableStorage.
    2. logger: the logger for the fetcher.
fetch_latest()
  • Description: fetch the latest data entry, sorted by the key.
fetch_oldest()
  • Description: fetch the oldest data entry, sorted by the key.
fetch_range(start_time, end_time)
  • Description: fetch the data whose key is within the range.

Documentation for Watcher Tool

Tool to monitor a specific latest key.

To initialize PartitionerWatcher

__init__(partitioner, logger, delay, timeout)
  • Description: initialize a PartitionerWatcher
  • Arguments:
    1. partitioner: the partitioner object to watch. It needs to have underlying storage of a ProtoTableStorage.
    2. logger: the logger for the watcher.
    3. delay: the seconds between each trial.
    4. timeout: the seconds of watch timeout.
watch_key(key)
  • Description: watch for the appearance of the given key in the latest partition.
  • Arguments:
    1. key: the key to watch.

Documentation for Registry Tool

The registry tool can be used as a function decorator to store functions in a dictionary. The following code shows the simple usage of this tool:

from pslx.tool.registry_tool import RegistryTool

registry = RegistryTool()
@registry.register("example_func")
def example_func():
    ... ...