union

The union proc is part of the set operators that can be used to join two streams back into one but applying some set operator to the items of the stream. In this case it allows points from both streams to pass and de-duplicates common points.

...
( ... , ....) | union(*fieldnames) | ...

Argument	Description	Required?
*fieldnames	list or tuple of field names to calculate the union on	No, default: time

unioning two streams

from flume import *

(
    (emit(points=[
        {'time': '2010-01-01T00:00:00.000Z', 'a': 0},
        {'time': '2010-01-01T00:01:00.000Z', 'a': 1},
        {'time': '2010-01-01T00:02:00.000Z', 'a': 2}
    ]),
    emit(points=[
        {'time': '2010-01-01T00:01:00.000Z', 'a': 1},
        {'time': '2010-01-01T00:02:00.000Z', 'a': 2},
        {'time': '2010-01-01T00:05:00.000Z', 'a': 3}
    ]))
    | union()
    | write('stdio')
).execute()

The above would produce the output:

{"a": 0, "time": "2010-01-01T00:00:00.000Z"}
{"a": 1, "time": "2010-01-01T00:01:00.000Z"}
{"a": 2, "time": "2010-01-01T00:02:00.000Z"}
{"a": 3, "time": "2010-01-01T00:05:00.000Z"}