reducers

reducers are responsible for handling a small piece of computing a value over a set of points. The way this works is that the reducer will receive individual update calls with each point that makes it to the reduce /put.

built-in

• count
• date
• funcr
• iterate
• math
• maximum
• minimum

write your own

Writing your own reducer is an easy task and should be a common one for various reducers not yet part of the core flume project. To write one you simply extend from the flume.reducer class and implement the following methods:

• __init__(self, ...) make sure to use the constructor to handle passing in the field names from the points that you will be manipulating.

• update(self, point) this is called for every point that makes it into the current interval of reduction. You should use the names of the fields you stored previously in the constructor to compute the value you wanted.

• result(self) should return the current value of the reduction being calculated. This means that if you're just counting the appearance of a field you'd return the current count.

• reset(self) reset is called at the end of every interval as defined in the call to the reduce proc.