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RedisGears Functions Runtime

Python RedisGears functions are run using an embedded Python interpreter. Each function uses a separate sub-interpreter. All functions share the same environment and dependencies. The environment is imported with several defaults.

The following sections describe the runtime environment.

Python Interpreter

RedisGears embeds a Python version 3.7.2+ interpreter.

All functions use that interpreter. Each call to RG.PYEXECUTE maintains its own globals dictionary that isolates its execution context from other calls. This means that all the functions submitted in that call share the interpreter and globals dictionary.

Further reference

For more information refer to:

Environment

The interpreter's environment can be extended with any dependent package that can later be imported and used by functions in their respective sub-interpreters.

Further reference

For more information about installing dependencies refer to:

GearsBuilder

The GearsBuilder class is imported to the runtime's environment by default.

It exposes the functionality of the function's context builder .

execute

The execute() function is imported to the runtime's environment by default.

This function executes an arbitrary Redis command.

Further reference

For more information about Redis commands refer to:

Python API 

def execute(command, *args)

Arguments

  • command : the command to execute
  • args : the command's arguments

Examples 

# Pings the server (reply should be 'PONG')
reply = execute('PING')

atomic

The atomic() Python context is imported to the runtime's environment by default.

The context ensures that all operations in it are executed atomically by blocking the main Redis process.

Python API 

class atomic()

Examples 

# Increments two keys atomically
def transaction(_):
    with atomic():
        execute('INCR', f'{{{hashtag()}}}:foo')
        execute('INCR', f'{{{hashtag()}}}:bar')

gb = GB('ShardsIDReader')
gb.foreach(transaction)
gb.run()

configGet

The configGet() function is imported to the runtime's environment by default.

This function fetches the current value of a RedisGears configuration option.

Python API 

def configGet(key)

Arguments

  • key : the configuration option key

Examples 

# Gets the current value for 'ProfileExecutions'
foo = configGet('ProfileExecutions')

gearsConfigGet

The gearsConfigGet() function is imported to the runtime's environment by default.

This function fetches the current value of a RedisGears configuration option and returns a default value if that key does not exist.

Python API 

def gearsConfigGet(key, default=None)

Arguments

  • key : the configuration option key
  • default : a default value

Examples 

# Gets the 'foo' configuration option key and defaults to 'bar'
foo = gearsConfigGet('foo', default='bar')

hashtag

The hashtag() function is imported to the runtime's environment by default.

This function returns a hashtag that maps to the lowest hash slot served by the local engine's shard. Put differently, it is useful as a hashtag for partitioning in a cluster.

Python API 

def hashtag()

Examples 

# Get the shard's hashtag
ht = hashtag()

log

The log() function is imported to the runtime's environment by default.

This function prints a message to Redis' log.

Python API 

def log(message, level='notice')

Arguments

  • message : the message to output
  • level : the message's log level can be one of these:
    • 'debug'
    • 'verbose'
    • 'notice'
    • 'warning'

Examples 

# Dumps every datum in the DB to the log for "debug" purposes
GB().foreach(lambda x: Log(str(x), level='debug')).run()