Context API

quixstreams.context

set_message_context

def set_message_context(context: Optional[MessageContext])

[VIEW SOURCE]

Set a MessageContext for the current message in the given contextvars.Context

NOTE: This is for advanced usage only. If you need to change the message key, StreamingDataFrame.to_topic() has an argument for it.

Example Snippet:

from quixstreams import Application, set_message_context, message_context

# Changes the current sdf value based on what the message partition is.
def alter_context(value):
    context = message_context()
    if value > 1:
        context.headers = context.headers + (b"cool_new_header", value.encode())
        set_message_context(context)

app = Application()
sdf = app.dataframe()
sdf = sdf.update(lambda value: alter_context(value))

Arguments:

context: instance of MessageContext

message_context

def message_context() -> MessageContext

[VIEW SOURCE]

Get a MessageContext for the current message, which houses most of the message

metadata, like: - key - timestamp - partition - offset

Example Snippet:

from quixstreams import Application, message_context

# Changes the current sdf value based on what the message partition is.

app = Application()
sdf = app.dataframe()
sdf = sdf.apply(lambda value: 1 if message_context().partition == 2 else 0)

Returns:

instance of MessageContext