Redis with iDB Storage

The branch adds a new iDB Disk Data Storage to redis. You can use the redis as database storage with iDB. And iDB can be used to replace the original RDB Disk Data Storage too.

Disk Data Storage Features Comparison

RDB Storage

Purpose: Redis is a memcache, but can save the memcached data to disk.

• Save all data to disk even if it is only once change occurs.
• Support Asynchronous saved only.
• much greater than the memory capacity of the storage will cause problems

iDB Storage

Purpose: the Key/value Database(Persistent data storage) with a memcache.

• Save changes only, not all.
• Support Synchronous or Asynchronous saved.
• No problem with large data storage.
• Support hierarchy key/value, like path of a key.
• Support subkeys with pagination or not.
• Support the local partition keys for pagination.
• support the multiple attributes of a key
  • the key name can not include any dot '.' char
    • if u wana use the '.' char in key name, u must escape it by ''
    • seperate the key and attribute by dot('.') char.
  • the attribute is always string.
  • the 'get key.value' is same as 'get key'
  • get/set key.attribute

if set the expired time, it will cache in memory only instead of saving to iDB. if set the negated expired time, it will cache in memory for the abs(expired_time) and save to iDB.

Known Issues for iDB

• [Replication] the full resynchronization can not send the whole data if the database size greater than the memcache.

Configuration

the new options added to redis.conf:

# enable/disable iDB storage
idb-enabled yes
# the store path for iDB
idb-path ./my.idb
# the max page size for idb
# 0 means do not enable the pagination(partition key).
idb-pagesize 0
# enable/disable sync write or async write on background.
idb-sync no
# enabled/disable the redis dump file(rdb) storage.
rdb-enabled no

Donot forget these options:

#maybe u wanna limit the memory cache size:
maxmemory 512mb
#it's a cache only now, so just remove any key accordingly to the LRU algorith
maxmemory-policy allkeys-lru

The database 0 means default and root database in iDB. The others database number can be visited in the default database(just keep compatibility):

select 1
set KeyName 1
select 2
set KeyName 2
select 0
get .db1/KeyName  #get KeyName in the database 1.
get .db2/KeyName  #get KeyName in the database 2.

Commands

New commands list here:

• subkeys [KeyPath [subkeysPattern [Count [skipCount]]]]
  • the subkeys will iterate all matched subkeys in the keyPath for iDB.
  • skipCount: skip the count of matched subkeys before.
  • count: return the count of matched subkeys. it should be less than or equ idb-pagesize(if idb-pagesize enabled).
  • eg, subkeys, will return all the keys in the iDB if idb-pagesize == 0.
  • Note: keys command only return all keys in the memory cache.
• Attribute operations: [todo these attributes are Disk IO directly, no memcache yet]
  • the attribute ".value" means the key's value.
  • the attribute ".type" means the key's type.
  • aset key attribute value: set the attribute of the key
  • aget/aexists/adel key attribute: get/(check exists)/del the attribute of the key
  • attrs key: list the attributes of the key(not fined)

Build

before building, you need ensure cmake installed, and run

git submodule update --init --recursive

if you update the deps/idb/ by git pull, you should make idb too:

cd deps/idb
git checkout master
git pull
make

Todo

• force to read the key's attributes from disk.
• the key's attributes should be cached in memory.
  • the simple way is treat the "." as reserved word, do not be allowed in key name.
• the current dbsize command only for the keys in memcache.
• the most of debug command only for the keys in memcache.
• ![Bug] AOF can not work on iDB. because AOF is still use dict(memcache) to save.
• !List, Set, Hash items should treat as subkey when saving to disk.
  • Or if items is very large to do so.
• !+ abstract new storage struct for memcache, aof, rdb, disk storage
• Exchange value should be as an atomic operation?
  • I use two dicts to keep the changed keys, one is dirtyKeys, another is dirtyQueue. (if asynchronous is enabled.)
  • modifies will be added to dirtyKeys if no saving.
  • any modifies will be added to dirtyQueue when bgsaving occurs.
  • the dirtyKeys will be empty and swap them(dirtyQueue, dirtyKeys) after saving
  • maybe it is no problem, redis is single thread app after all.

Redis

Where to find complete Redis documentation?

======= This README is just a fast quick start document. You can find more detailed documentation at http://redis.io.

What is Redis?

Redis is often referred as a data structures server. What this means is that Redis provides access to mutable data structures via a set of commands, which are sent using a server-client model with TCP sockets and a simple protocol. So different processes can query and modify the same data structures in a shared way.

Data structures implemented into Redis have a few special properties:

• Redis cares to store them on disk, even if they are always served and modified into the server memory. This means that Redis is fast, but that is also non-volatile.
• Implementation of data structures stress on memory efficiency, so data structures inside Redis will likely use less memory compared to the same data structure modeled using an high level programming language.
• Redis offers a number of features that are natural to find in a database, like replication, tunable levels of durability, cluster, high availability.

Another good example is to think of Redis as a more complex version of memcached, where the operations are not just SETs and GETs, but operations to work with complex data types like Lists, Sets, ordered data structures, and so forth.

If you want to know more, this is a list of selected starting points:

• Introduction to Redis data types. http://redis.io/topics/data-types-intro
• Try Redis directly inside your browser. http://try.redis.io
• The full list of Redis commands. http://redis.io/commands
• There is much more inside the Redis official documentation. http://redis.io/documentation

Building Redis

Redis can be compiled and used on Linux, OSX, OpenBSD, NetBSD, FreeBSD. We support big endian and little endian architectures, and both 32 bit and 64 bit systems.

It may compile on Solaris derived systems (for instance SmartOS) but our support for this platform is best effort and Redis is not guaranteed to work as well as in Linux, OSX, and *BSD there.

It is as simple as:

% make

You can run a 32 bit Redis binary using:

% make 32bit

After building Redis is a good idea to test it, using:

% make test

Fixing build problems with dependencies or cached build options

Redis has some dependencies which are included into the deps directory. make does not rebuild dependencies automatically, even if something in the source code of dependencies is changes.

When you update the source code with git pull or when code inside the dependencies tree is modified in any other way, make sure to use the following command in order to really clean everything and rebuild from scratch:

make distclean

This will clean: jemalloc, lua, hiredis, linenoise.

Also if you force certain build options like 32bit target, no C compiler optimizations (for debugging purposes), and other similar build time options, those options are cached indefinitely until you issue a make distclean command.

Fixing problems building 32 bit binaries

If after building Redis with a 32 bit target you need to rebuild it with a 64 bit target, or the other way around, you need to perform a make distclean in the root directory of the Redis distribution.

In case of build errors when trying to build a 32 bit binary of Redis, try the following steps:

• Install the packages libc6-dev-i386 (also try g++-multilib).
• Try using the following command line instead of make 32bit: make CFLAGS="-m32 -march=native" LDFLAGS="-m32"

Allocator

Selecting a non-default memory allocator when building Redis is done by setting the MALLOC environment variable. Redis is compiled and linked against libc malloc by default, with the exception of jemalloc being the default on Linux systems. This default was picked because jemalloc has proven to have fewer fragmentation problems than libc malloc.

To force compiling against libc malloc, use:

% make MALLOC=libc

To compile against jemalloc on Mac OS X systems, use:

% make MALLOC=jemalloc

Verbose build

Redis will build with a user friendly colorized output by default. If you want to see a more verbose output use the following:

% make V=1

Running Redis

To run Redis with the default configuration just type:

% cd src
% ./redis-server

If you want to provide your redis.conf, you have to run it using an additional parameter (the path of the configuration file):

% cd src
% ./redis-server /path/to/redis.conf

It is possible to alter the Redis configuration passing parameters directly as options using the command line. Examples:

% ./redis-server --port 9999 --slaveof 127.0.0.1 6379
% ./redis-server /etc/redis/6379.conf --loglevel debug

All the options in redis.conf are also supported as options using the command line, with exactly the same name.

Playing with Redis

You can use redis-cli to play with Redis. Start a redis-server instance, then in another terminal try the following:

% cd src
% ./redis-cli
redis> ping
PONG
redis> set foo bar
OK
redis> get foo
"bar"
redis> incr mycounter
(integer) 1
redis> incr mycounter
(integer) 2
redis>

You can find the list of all the available commands at http://redis.io/commands.

Installing Redis

In order to install Redis binaries into /usr/local/bin just use:

% make install

You can use make PREFIX=/some/other/directory install if you wish to use a different destination.

Make install will just install binaries in your system, but will not configure init scripts and configuration files in the appropriate place. This is not needed if you want just to play a bit with Redis, but if you are installing it the proper way for a production system, we have a script doing this for Ubuntu and Debian systems:

% cd utils
% ./install_server.sh

The script will ask you a few questions and will setup everything you need to run Redis properly as a background daemon that will start again on system reboots.

You'll be able to stop and start Redis using the script named /etc/init.d/redis_<portnumber>, for instance /etc/init.d/redis_6379.

Code contributions

Note: by contributing code to the Redis project in any form, including sending a pull request via Github, a code fragment or patch via private email or public discussion groups, you agree to release your code under the terms of the BSD license that you can find in the COPYING file included in the Redis source distribution.

Please see the CONTRIBUTING file in this source distribution for more information.

Enjoy!