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During the AOF rewrite process, the parent process needs to accumulate the new writes in an in-memory buffer: when the child will terminate the AOF rewriting process this buffer (that ist the difference between the dataset when the rewrite was started, and the current dataset) is flushed to the new AOF file. We used to implement this buffer using an sds.c string, but sds.c has a 2GB limit. Sometimes the dataset can be big enough, the amount of writes so high, and the rewrite process slow enough that we overflow the 2GB limit, causing a crash, documented on github by issue #504. In order to prevent this from happening, this commit introduces a new system to accumulate writes, implemented by a linked list of blocks of 10 MB each, so that we also avoid paying the reallocation cost. Note that theoretically modern operating systems may implement realloc() simply as a remaping of the old pages, thus with very good performances, see for instance the mremap() syscall on Linux. However this is not always true, and jemalloc by default avoids doing this because there are issues with the current implementation of mremap(). For this reason we are using a linked list of blocks instead of a single block that gets reallocated again and again. The changes in this commit lacks testing, that will be performed before merging into the unstable branch. This fix will not enter 2.4 because it is too invasive. However 2.4 will log a warning when the AOF rewrite buffer is near to the 2GB limit.
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
Building Redis
--------------
Redis can be compiled and used on Linux, OSX, OpenBSD, NetBSD, FreeBSD.
We support big endian and little endian architectures.
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
NOTE: if after building Redis with a 32 bit target you need to rebuild it
with a 64 bit target you need to perform a "make clean" in the root
directory of the Redis distribution.
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 here:
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
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.
Enjoy!
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