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yrmcds is a memory object caching system with master/slave replication.

Currently, yrmcds supports two protocols: the first is an enhanced memcached, and another is a protocol to implement distributed resource counters.

Since the memcached protocol is perfectly compatible with the original implementation, yrmcds can be used as a drop-in replacement for memcached. Thanks to its virtual-IP based replication system, existing applications can obtain high-available memcached-compatible service without any modifications.

A companion client library libyrmcds and a PHP extension are also available.

yrmcds was developed originally for kintone.com.

License

yrmcds is licensed under the BSD 2-clause license.

The source code contains a SipHash implementation borrowed from csiphash which is licensed under the MIT license.

Features

• Complete memcached text and binary protocols with these extensions:
  • Server-side locking
  • Dump keys
• Distributed resource counter protocol.
• Optional memory security to store confidential information like SSL session data.
• Large objects can be stored in temporary files, not in memory.
• Virtual-IP based master-slave replication.
  • Automatic fail-over
  • Automatic recovery of redundancy.
• Global LRU eviction / no slab distribution problem.
  • Unlike memcached, yrmcds is not involved with slabs problems. (1, 2)

A companion client library and a PHP extension are also available.

See also usage guide, future plans, differences from memcached, design notes and some benchmark results.

Prerequisites

• Linux.
• GCC or clang with C++17 support.
• GNU make.

Build

Just run make.

yrmcds runs faster when linked with TCMalloc. On Debian/Ubuntu, install libgoogle-perftools-dev package to prepare TCMalloc.

The makefile automatically detects TCMalloc if available.

Install

On Ubuntu, sudo make install installs yrmcds under /usr/local. What make install does are:

• Install yrmcdsd under /usr/local/sbin.
• Install service start script for systemd or upstart.
• Install logrotate script.
• Create /etc/yrmcds.conf.

About the name

The name yrmcds was taken from "Ymmt's Replicating MemCacheD for Sessions".
As it reads, yrmcds was developed mainly for session storage.

The correct pronunciation sounds like: "Yo-Ru-Mac-Do" (夜マクド in Japanese).