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Simple, distributed sorted sets with redis

Project description

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Simple, generic sorted sets backed by Redis that can be used to coordinate distributed systems. Unlike more common distribution libraries, e.g. Celery or RQ, redset avoids duplicate work for certain use-cases by maintaining a set of tasks instead of a list or queue.

Features

  • Safe for multiple producers and consumers
  • Seamless use with Python objects using serializers
  • No worker daemons to run, no client processes to maintain
  • Simple, easy-to-read implementation
  • Mimics Python’s native set interface
  • Battle-tested

Simple example

import json
import redis

from redset import TimeSortedSet

r = redis.Redis()
ss = TimeSortedSet(r, 'important_json_biz', serializer=json)

ss.add({'foo': 'bar1'})
ss.add({'foo': 'bar2'})

ss.add({'foo': 'bar3'})
ss.add({'foo': 'bar3'})

len(ss)
# 3


# ...some other process A

ss.peek()
# {'foo': 'bar1'}

ss.pop()
# {'foo': 'bar1'}


# ...meanwhile in process B (at exactly same time as A's pop)

ss.take(2)
# [{'foo': 'bar2'}, {'foo': 'bar3'}]

Docs

Here

About

This software was developed at Percolate, where we use it for all sorts of things that involve maintaining synchronized sets of things across process boundaries. A common use-case is to use redset for coordinating time-sensitive tasks where duplicate requests may be generated.

Redset is unopinionated about how consumers look or behave. Want to have a plain ‘ol Python consumer managed by supervisor? Fine. Want to be able to pop off items from within a celery job? Great. Redset has no say in where or how it is used: mechanism, not policy.

Usage concepts

redset.SortedSet and its subclasses can be instantiated with a few paramters that are notable.

Specifying a serializer

Since Redis only stores primitive numbers and strings, handling serialization and deserialization is a key part of making redset set usage simple in Python.

A serializer instance can be passed (which adheres to the redset.interfaces.Serializer interface, though it need not subclass it) to automatically handle packing and unpacking items managed with redset.

Specifying a scorer

A callable that specifies how to generate a score for items being added can also be passed to SortedSet’s constructor as scorer. This callable takes one argument, which is the item object (i.e. the item before serialization) to be “scored.”

Project details


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