dump_redis_to_disk.py

"""
Copies all keys from the source Redis host to the destination Redis host.
Useful to migrate Redis instances where commands like SLAVEOF and MIGRATE are
restricted (e.g. on Amazon ElastiCache).

The script scans through the keyspace of the given database number and uses
a pipeline of DUMP and RESTORE commands to migrate the keys.

Requires Redis 2.8.0 or higher.

Python requirements:
redis==2.10.3
"""
import os
import redis
from redis.exceptions import ResponseError

def migrate():
    source = redis.Redis(os.getenv('REDIS_HOST'))

    size = source.dbsize()

    if size == 0:
        print 'No keys found.'
        return

    COUNT = 2000 # scan size

    non_existing = 0
    already_existing = 0
    cursor = 0

    while True:
        cursor, keys = source.scan(cursor, count=COUNT)
        pipeline = source.pipeline()
        for key in keys:
            pipeline.pttl(key)
            pipeline.dump(key)
        result = pipeline.execute()

        for key, ttl, data in zip(keys, result[::2], result[1::2]):
            if ttl is None:
                ttl = 0
            if data != None:
		print('%s %s' % (key, data.encode('base64').replace('\n', '')))
            else:
                non_existing += 1

        if cursor == 0:
            break


if __name__ == '__main__':
    migrate()