Concurrent priority queue in redis?
I would like to implement a concurrent priority queue in Redis, with multiple processes on different machines adding items (with scores) and multiple other processes popping these items, lowest score first.
A simple queue can be implemented with LPUSH and RPOP.
Using a ZSET, I can add the items using ZADD and pop them with ZRANGE and ZREM, as long as there is only one reader.
For multiple readers I think I need something like ZPOP which combines ZRANGE and ZREM in a single atomic operation. Otherwise two readers may get the same item from ZRANGE before either can ZREM it. Retrying if ZREM returns 0 would work but is not desirable.
Is there some way I can do this using the current Redis commands? Is there any reason this hasn't been added to Redis already? It seems like it would be a pretty simple command to implement.
You can guarantee atomicity if you use a Lua script that does the ZRANGE & ZREM or with a MULTI/EXEC block. This will prevent multiple workers from interfering with each other.
I assume that ZPOP wasn't put in in the first place because it isn't a common use case and, when needed, it can be easily scripted.
Priority queue in Redis aka ZPOP – Charles Nagy, Notice that we don't need any special locking or concurrency control because we check the return value of zrem command. If it managed to� Now you have a perfect priority queue implementation using basic redis commands. ZREM vs ZREMRANGEBYRANK. ZREM has the time complexity (quoting redio.io): O(M*log(N)) with N being the number of elements in the sorted set and M the number of elements to be removed. ZREMRANGEBYRANK’s time complecity:
you can use redis command: watch
WATCH zset element = ZRANGE zset 0 0 MULTI ZREM zset element EXEC
if exec fails (return a null reply), just repeat those commands.
6.4.1 First-in, first-out queues, why, and will implement a worker process that can be run in parallel to send multiple If there are no high-priority items, then items in the medium-priority level� Concurrent priority queue in redis? 0. Redis Sorted Set Member Size and Performance. 0. Set options for ZADD command in laravel redis. 2. Redis sorted set based on
gabfl/redis-priority-queue: Simple Redis work queue with , redis-priority-queue is a simple work queue similar to Redis lists with the following added features: An item can be added with a priority (between -9007199254740992 and 9007199254740992) Queues are automatically de-duplicated (duplicate items are voided when pushing them) I ended up storing in <thread-specific-processing-queue> which is a redis z-set, and not a queue. So the expiry time is the score of the element in the z-set. Then I use redis scheduling pattern to scan the z-set based on score and then put back the expired keys to main queue. – Mopparthy Ravindranath Jul 28 '15 at 8:20
Distributed Java Queues on Top of Redis, Messages may be sent according to their age or according to some other predefined priority ranking. In order to store these pending messages,� Redis Connection Settings. By default, Kue will connect to Redis using the client default settings (port defaults to 6379, host defaults to 127.0.0.1, prefix defaults to q). Queue#createQueue(options) accepts redis connection options in options.redis key.
RPOPLPUSH – Redis, A simple form of queue is often obtained pushing values into a list in the producer side, with the smallest delay possible, using a number of parallel workers. REDIS_START_URLS_BATCH_SIZE : int (deprecated by CONCURRENT_REQUESTS) Default number of messages to fetch from redis on each attempt. REDIS_START_URLS_AS_SET : bool (default: True) Use SET operations to retrieve messages from the redis queue. REDIS_ENCODING : str (default: "utf-8") Default encoding to use when decoding messages from redis queue
BLPOP – Redis, Priority ordering details. If the client tries to blocks for multiple keys, but at least one key contains elements, the returned key / element pair is the first key from left � php artisan queue:table php artisan migrate Redis. In order to use the redis queue driver, you should configure a Redis database connection in your config/database.php configuration file. Redis Cluster. If your Redis queue connection uses a Redis Cluster, your queue names must contain a key hash tag. This is required in order to ensure all of