255 lines
12 KiB
Markdown
255 lines
12 KiB
Markdown
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[](https://travis-ci.org/JohnSully/KeyDB) [](https://gitter.im/KeyDB/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
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[](https://stackshare.io/eq-alpha-technology-inc/eq-alpha-technology-inc)
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What is KeyDB?
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--------------
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KeyDB is a high performance fork of Redis focusing on multithreading, memory efficiency, and high throughput. In addition to multithreading KeyDB also has features only available in Redis Enterprise such as [Active Replication](https://github.com/JohnSully/KeyDB/wiki/Active-Replication), [FLASH storage](https://github.com/JohnSully/KeyDB/wiki/FLASH-Storage) support, and some not available at all such as direct backup to AWS S3.
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On the same hardware KeyDB can perform twice as many queries per second as Redis, with 60% lower latency.
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KeyDB has full compatibility with the Redis protocol, modules, and scripts. This includes full support for transactions, and atomic execution of scripts. For more information see our architecture section below.
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Try our docker container: https://hub.docker.com/r/eqalpha/keydb
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Talk on Gitter: https://gitter.im/KeyDB
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[Subscribe to the KeyDB mailing list](https://eqalpha.us20.list-manage.com/subscribe/post?u=978f486c2f95589b24591a9cc&id=4ab9220500)
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Management GUI: We recommend [FastoNoSQL](https://fastonosql.com/) which has official KeyDB support.
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New: Active Replica Support
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---------------------------
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New! KeyDB now has support for Active Replicas. This feature greatly simplifies hot-spare failover and allows you to distribute writes over replicas instead of just a single master. For more information [see the wiki page](https://github.com/JohnSully/KeyDB/wiki/Active-Replication).
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Why fork Redis?
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---------------
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The Redis maintainers have continually reiterated that they do not plan to support multithreading. While we have great respect for the redis team, we feel the analysis justifying this decision is incorrect. In addition we wanted open source implementations of features currently only available in proprietary modules. We feel a fork is the best way to accelerate development in the areas of most interest to us.
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We plan to track the Redis repo closely and hope our projects can learn from each other.
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Benchmarking KeyDB
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------------------
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<img src=https://cdn-images-1.medium.com/max/1400/1*s7mTb7Qb0kxc951mz8bdgA.png width=420 height=300/><img src=https://cdn-images-1.medium.com/max/1400/1*R00A5U4AFGohGOYHMfT6fA.png height=300/>
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Please note keydb-benchmark and redis-benchmark are currently single threaded and too slow to properly benchmark KeyDB. We recommend using a redis cluster benchmark tool such as [memtier](https://github.com/RedisLabs/memtier_benchmark). Please ensure your machine has enough cores for both KeyDB and memteir if testing locally. KeyDB expects exclusive use of any cores assigned to it.
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For more details on how we benchmarked KeyDB along with performance numbers check out our blog post: [Redis Should Be Multithreaded](https://medium.com/@john_63123/redis-should-be-multi-threaded-e28319cab744?source=friends_link&sk=7ce8e9fe3ec8224a4d27ef075d085457)
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New Configuration Options
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-------------------------
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With new features comes new options:
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server-threads N
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server-thread-affinity [true/false]
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The number of threads used to serve requests. This should be related to the number of queues available in your network hardware, *not* the number of cores on your machine. Because KeyDB uses spinlocks to reduce latency; making this too high will reduce performance. We recommend using 4 here. By default this is set to one.
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scratch-file-path /path
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If you would like to use the [FLASH backed](https://github.com/JohnSully/KeyDB/wiki/FLASH-Storage) storage this option configures the directory for KeyDB's temporary files. This feature relies on snapshotting to work so must be used on a BTRFS filesystem. ZFS may also work but is untested. With this feature KeyDB will use RAM as a cache and page to disk as necessary. NOTE: This requires special compilation options, see Building KeyDB below.
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db-s3-object /path/to/bucket
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If you would like KeyDB to dump and load directly to AWS S3 this option specifies the bucket. Using this option with the traditional RDB options will result in KeyDB backing up twice to both locations. If both are specified KeyDB will first attempt to load from the local dump file and if that fails load from S3. This requires the AWS CLI tools to be installed and configured which are used under the hood to transfer the data.
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All other configuration options behave as you'd expect. Your existing configuration files should continue to work unchanged.
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Building KeyDB
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--------------
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KeyDB can be compiled and is tested for use on Linux. KeyDB currently relies on SO_REUSEPORT's load balancing behavior which is available only in Linux. When we support marshalling connections across threads we plan to support other operating systems such as FreeBSD.
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Install dependencies:
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% sudo apt install build-essential nasm autotools-dev autoconf libjemalloc-dev tcl tcl-dev uuid-dev
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Compiling is as simple as:
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% make
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You can enable flash support with (Note: autoconf and autotools must be installed):
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% make MALLOC=memkind
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Fixing build problems with dependencies or cached build options
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---------
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KeyDB has some dependencies which are included into the `deps` directory.
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`make` does not automatically rebuild dependencies even if something in
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the source code of dependencies changes.
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When you update the source code with `git pull` or when code inside the
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dependencies tree is modified in any other way, make sure to use the following
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command in order to really clean everything and rebuild from scratch:
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make distclean
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This will clean: jemalloc, lua, hiredis, linenoise.
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Also if you force certain build options like 32bit target, no C compiler
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optimizations (for debugging purposes), and other similar build time options,
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those options are cached indefinitely until you issue a `make distclean`
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command.
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Fixing problems building 32 bit binaries
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---------
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If after building KeyDB with a 32 bit target you need to rebuild it
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with a 64 bit target, or the other way around, you need to perform a
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`make distclean` in the root directory of the KeyDB distribution.
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In case of build errors when trying to build a 32 bit binary of KeyDB, try
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the following steps:
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* Install the packages libc6-dev-i386 (also try g++-multilib).
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* Try using the following command line instead of `make 32bit`:
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`make CFLAGS="-m32 -march=native" LDFLAGS="-m32"`
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Allocator
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---------
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Selecting a non-default memory allocator when building KeyDB is done by setting
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the `MALLOC` environment variable. KeyDB is compiled and linked against libc
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malloc by default, with the exception of jemalloc being the default on Linux
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systems. This default was picked because jemalloc has proven to have fewer
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fragmentation problems than libc malloc.
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To force compiling against libc malloc, use:
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% make MALLOC=libc
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To compile against jemalloc on Mac OS X systems, use:
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% make MALLOC=jemalloc
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Verbose build
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-------------
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KeyDB will build with a user friendly colorized output by default.
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If you want to see a more verbose output use the following:
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% make V=1
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Running KeyDB
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-------------
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To run KeyDB with the default configuration just type:
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% cd src
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% ./keydb-server
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If you want to provide your keydb.conf, you have to run it using an additional
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parameter (the path of the configuration file):
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% cd src
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% ./keydb-server /path/to/keydb.conf
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It is possible to alter the KeyDB configuration by passing parameters directly
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as options using the command line. Examples:
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% ./keydb-server --port 9999 --replicaof 127.0.0.1 6379
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% ./keydb-server /etc/keydb/6379.conf --loglevel debug
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All the options in keydb.conf are also supported as options using the command
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line, with exactly the same name.
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Playing with KeyDB
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------------------
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You can use keydb-cli to play with KeyDB. Start a keydb-server instance,
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then in another terminal try the following:
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% cd src
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% ./keydb-cli
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keydb> ping
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PONG
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keydb> set foo bar
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OK
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keydb> get foo
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"bar"
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keydb> incr mycounter
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(integer) 1
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keydb> incr mycounter
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(integer) 2
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keydb>
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You can find the list of all the available commands at http://redis.io/commands.
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Installing KeyDB
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-----------------
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In order to install KeyDB binaries into /usr/local/bin just use:
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% make install
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You can use `make PREFIX=/some/other/directory install` if you wish to use a
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different destination.
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Make install will just install binaries in your system, but will not configure
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init scripts and configuration files in the appropriate place. This is not
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needed if you want just to play a bit with KeyDB, but if you are installing
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it the proper way for a production system, we have a script doing this
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for Ubuntu and Debian systems:
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% cd utils
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% ./install_server.sh
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_Note_: `install_server.sh` will not work on Mac OSX; it is built for Linux only.
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The script will ask you a few questions and will setup everything you need
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to run KeyDB properly as a background daemon that will start again on
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system reboots.
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You'll be able to stop and start KeyDB using the script named
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`/etc/init.d/keydb_<portnumber>`, for instance `/etc/init.d/keydb_6379`.
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Multithreading Architecture
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---------------------------
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KeyDB works by running the normal Redis event loop on multiple threads. Network IO, and query parsing are done concurrently. Each connection is assigned a thread on accept(). Access to the core hash table is guarded by spinlock. Because the hashtable access is extremely fast this lock has low contention. Transactions hold the lock for the duration of the EXEC command. Modules work in concert with the GIL which is only acquired when all server threads are paused. This maintains the atomicity guarantees modules expect.
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Unlike most databases the core data structure is the fastest part of the system. Most of the query time comes from parsing the REPL protocol and copying data to/from the network.
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Future work:
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- Allow rebalancing of connections to different threads after the connection
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- Allow multiple readers access to the hashtable concurrently
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Docker Build
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------------
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Run the following commands for a full source download and build:
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```
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git clone git@github.com:JohnSully/KeyDB.git
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docker run -it --rm -v `pwd`/KeyDB:/build -w /build devopsdood/keydb-builder make
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```
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Then you have fresh binaries built, you can also pass any other options to the make command above after the word make. E.g.
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```docker run -it --rm -v `pwd`/KeyDB:/build -w /build devopsdood/keydb-builder make MAllOC=memkind```
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The above commands will build you binaries in the src directory. Standard `make install` without Docker command will work after if you wish to install
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If you'd prefer you can build the Dockerfile in the repo instead of pulling the above container for use:
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`docker build -t KeyDB .`
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Code contributions
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-----------------
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Note: by contributing code to the KeyDB project in any form, including sending
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a pull request via Github, a code fragment or patch via private email or
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public discussion groups, you agree to release your code under the terms
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of the BSD license that you can find in the COPYING file included in the KeyDB
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source distribution.
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Please see the CONTRIBUTING file in this source distribution for more
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information.
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