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Redis Storage Driver Design (Zaqar)

Revision as of 05:08, 9 August 2014 by Prashanthr (talk | contribs)


Redis is an in memory key-value datastore which can organize data as strings, hashes, lists, sets, sorted sets, bitmaps and hyperloglogs. Being In-memory makes it in ideal candidate for high load, low latency messages.

The main use cases of the driver are listed below:

1. High-throughput (2K+ messages/sec per queue)

2. Lots of small messages (<= 1K)

3. Messages are short-lived (minutes, not hours)

4. High durability is optional (2 copies, RAM only)

5. HA is still very important

Components of the basic driver

The basic driver includes support for a single instance redis store as a data backend.

The driver supports 6 main required functions of a marconi storage driver which are:

Message Controller

Helps organize messages scoped by every queue.

Organization of Data

Message id's list ( Redis Sorted Set )
Each queue in the system has a set of message ids currently in the queue. The list is sorted based on a ranking which is incremented atomically using the counter(MESSAGE_RANK_COUNTER_SUFFIX) also stored in the database for every queue.

Messages(Redis Hash):

Each message is stored using the UUID of the message as the redis key. The datastructure has the following information.
NOTE: This datastructure is serialized using msgpack.

Name Field
id id
created iso cr_iso
ttl t
expires e
body b
claim c
claim expiry time c.e
client uuid u
created time cr

Queue Controller

Queues are scoped by project, which is prefixed to the queue name.

Queues ( Redis Sorted Set ):
Id: queues_set


Name Field
name <project-id.queue-name>

The set helps faster existence checks, while the list helps paginated retrieval of queues.

Queue Information (Redis Hash):

This Data structure holds all meta information about a queue.

Scope: <project-id_q-name>

Name Field
count(size) c
claimed cl
metadata m
creation time t

Claims Controller

Claims list ( Redis Set ) contains claim ids active for a queue.

Redis ID: <project-id_q-name>

Claim info(Redis Hash):

Contains the metadata information for a particular claim.

Name Field
ttl t
grace g
id if
claim c
client UUID u

Catalogue Controller


Pools Controller


Current Status

The basic driver is a "Work in Progress" and is expected to be a part of the code base by Juno-3 deadline (Sept 4th 2014). The clustering and persistence extension is expected to be developed before the end of Kilo. It is also one of the requirements for the graduation of Marconi.


Blueprint URL Functionality
[1] Redis as an alternative driver for MongoDB
[2] Redis Storage Driver for Marconi

Submitted Patches

Patch URL Implemented Feature
[3] Messages and Queue Controllers
[4] Claims Controller
[5] Pools and Catalog Controllers

Future Work

1. Support Async connections to the redis database.