Corvus

Corvus is a fast and lightweight redis cluster proxy for redis 3.0 with cluster mode enabled.

Why

Most redis client implementations don't support redis cluster. We have a lot of services relying on redis, which are written in Python, Java, Go, Nodejs etc. It's hard to provide redis client libraries for multiple languages without breaking compatibilities. We used twemproxy before, but it relies on sentinel for high availabity, it also requires restarting to add or remove backend redis instances, which causes service interruption. And twemproxy is single threaded, we have to deploy multiple twemproxy instances for large number of clients, which causes the sa headaches.

Therefore, we made corvus.

Features

• Fast.
• Lightweight.
• Painless upgrade to official redis cluster from twemproxy.
• Multiple threading.
• Reuseport support.
• Pipeline support.
• Statsd integration.
• Syslog integration.
• Can direct read operations to slaves.

Performance

See details in our test results.

Requirements

• Linux >= 3.9
• Redis <= 3.0.7 (For version up to/including 0.2.3)

Build

If use the releases downloaded from releases page, just make:

$ make

With debug mode enabled:

make debug

If build from latest source:

git clone https://github.com/eleme/corvus.git
cd corvus
git submodule update --init
make deps # need autoconf
make

Binary can be found at ./src/corvus.

Configuration

Example configuration file is at corvus.conf.

Usage

$ ./src/corvus path/to/corvus.conf

Commands

• All single-key commands (like SET, GET, INCR..) are supported.
• Batch commands are split into multiple single-key commands.
• Commands performing complex multi-key operations like unions or intersections are available as well as long as the keys all belong to the same node.

Modified commands

• MGET: split to multiple GET.
• MSET: split to multiple SET.
• DEL: split to multiple single key DEL.
• EXISTS: split to multiple single key EXISTS.
• PING: ignored and won't be forwarded.
• INFO, TIME: won't be forwarded to backend redis, information collected in proxy will be returned.
• SLOWLOG: return the slowlogs saved by corvus itself. Note that unlike redis, in the slowlog entry there's an additional remote latency field before the total latency field. The slowlog will also log the slowest sub command for multiple-key commands: MGET, MSET, DEL, EXISTS. The total latency of sub cmd entry will just be the same as its parent cmd.
• AUTH: do authentication in proxy.
• CONFIG: support get, set, and rewrite sub-command to retrieve and manipulate corvus config.
• SELECT: ignored if index is 0, won't be forwarded.

Restricted commands

• EVAL: at least one key should be given. If there are multiple keys, all of them should belong to the same node.

The following commands require all argument keys to belong to the same redis node:

• SORT.
• RPOP, LPUSH.
• SDIFF, SDIFFSTORE, SINTER, SINTERSTORE, SMOVE, SUNION, SUNIONSTORE.
• ZINTERSTORE, ZUNIONSTORE.
• PFCOUNTE, PFMERGE.

Unsupported commands

The following commands are not available, such as KEYS, we can't search keys across all backend redis instances.

• KEYS, MIGRATE, MOVE, OBJECT, RANDOMKEY, RENAME, RENAMENX, SCAN, WAIT.
• BITOP, MSETNX
• BLPOP, BRPOP, BRPOPLPUSH.
• PSUBSCRIBE, PUBLISH, PUBSUB, PUNSUBSCRIBE, SUBSCRIBE, UNSUBSCRIBE.
• EVALSHA, SCRIPT.
• DISCARD, EXEC, MULTI, UNWATCH, WATCH.
• CLUSTER.
• ECHO, QUIT.
• BGREWRITEAOF, BGSAVE, CLIENT, COMMAND, CONFIG, DBSIZE, DEBUG, FLUSHALL, FLUSHDB, LASTSAVE, MONITOR, ROLE, SAVE, SHUTDOWN, SLAVEOF, SYNC.

License

MIT. Copyright (c) 2016 Eleme Inc.

See LICENSE for details.