twemproxy

twemproxy (nutcracker) twemproxy (pronounced "two-em-proxy"), aka nutcracker is a fast and lightweight proxy for memcached and redis protocol. It was built primarily to reduce the number of connections to the caching servers on the backend. This, together with protocol pipelining and sharding enables you to horizontally scale your distributed caching architecture. Build To build twemproxy 0.5.0+ from distribution tarball: $ ./configure $ make $ sudo make install To build twemproxy 0.5.0+ from distribution tarball in debug mode: $ CFLAGS="-ggdb3 -O0" ./configure --enable-debug=full $ make $ sudo make install To build twemproxy from source with debug logs enabled and assertions enabled: $ git clone git@github.com:twitter/twemproxy.git $ cd twemproxy $ autoreconf -fvi $ ./configure --enable-debug=full $ make $ src/nutcracker -h A quick checklist: Use newer version of gcc (older version of gcc has problems) Use CFLAGS="-O1" ./configure && make Use CFLAGS="-O3 -fno-strict-aliasing" ./configure && make autoreconf -fvi && ./configure needs automake and libtool to be installed make check will run unit tests. Older Releases Distribution tarballs for older twemproxy releases (<= 0.4.1) can be found on Google Drive. The build steps are the same (./configure; make; sudo make install). Features Fast. Lightweight. Maintains persistent server connections. Keeps connection count on the backend caching servers low. Enables pipelining of requests and responses. Supports proxying to multiple servers. Supports multiple server pools simultaneously. Shard data automatically across multiple servers. Implements the complete memcached ascii and redis protocol. Easy configuration of server pools through a YAML file. Supports multiple hashing modes including consistent hashing and distribution. Can be configured to disable nodes on failures. Observability via stats exposed on the stats monitoring port. Works with Linux, *BSD, OS X and SmartOS (Solaris) Help Usage: nutcracker [-?hVdDt] [-v verbosity level] [-o output file] [-c conf file] [-s stats port] [-a stats addr] [-i stats interval] [-p pid file] [-m mbuf size] Options: -h, --help : this help -V, --version : show version and exit -t, --test-conf : test configuration for syntax errors and exit -d, --daemonize : run as a daemon -D, --describe-stats : print stats description and exit -v, --verbose=N : set logging level (default: 5, min: 0, max: 11) -o, --output=S : set logging file (default: stderr) -c, --conf-file=S : set configuration file (default: conf/nutcracker.yml) -s, --stats-port=N : set stats monitoring port (default: 22222) -a, --stats-addr=S : set stats monitoring ip (default: 0.0.0.0) -i, --stats-interval=N : set stats aggregation interval in msec (default: 30000 msec) -p, --pid-file=S : set pid file (default: off) -m, --mbuf-size=N : set size of mbuf chunk in bytes (default: 16384 bytes) Zero Copy In twemproxy, all the memory for incoming requests and outgoing responses is allocated in mbuf. Mbuf enables zero-copy because the same buffer on which a request was received from the client is used for forwarding it to the server. Similarly the same mbuf on which a response was received from the server is used for forwarding it to the client. Furthermore, memory for mbufs is managed using a reuse pool. This means that once mbuf is allocated, it is not deallocated, but just put back into the reuse pool. By default each mbuf chunk is set to 16K bytes in size. There is a trade-off between the mbuf size and number of concurrent connections twemproxy can support. A large mbuf size reduces the number of read syscalls made by twemproxy when reading requests or responses. However, with a large mbuf size, every active connection would use up 16K bytes of buffer which might be an issue when twemproxy is handling large number of concurrent connections from clients. When twemproxy is meant to handle a large number of concurrent client connections, you should set chunk size to a small value like 512 bytes using the -m or --mbuf-size=N argument. Configuration Twemproxy can be configured through a YAML file specified by the -c or --conf-file command-line argument on process start. The configuration file is used to specify the server pools and the servers within each pool that twemproxy manages. The configuration files parses and understands the following keys: listen: The listening address and port (name:port or ip:port) or an absolute path to sock file (e.g. /var/run/nutcracker.sock) for this server pool. client_connections: The maximum number of connections allowed from redis clients. Unlimited by default, though OS-imposed limitations will still apply. hash: The name of the hash function. Possible values are: one_at_a_time md5 crc16 crc32 (crc32 implementation compatible with libmemcached) crc32a (correct crc32 implementation as per the spec) fnv1_64 fnv1a_64 (default) fnv1_32 fnv1a_32 hsieh murmur jenkins hash_tag: A two character string that specifies the part of the key used for hashing. Eg "{}" or "$$". Hash tag enable mapping different keys to the same server as long as the part of the key within the tag is the same. distribution: The key distribution mode for choosing backend servers based on the computed hash value. Possible values are: ketama (default, recommended. An implementation of https://en.wikipedia.org/wiki/Consistent_hashing) modula (use hash modulo number of servers to choose the backend) random (choose a random backend for each key of each request) timeout: The timeout value in msec that we wait for to establish a connection to the server or receive a response from a server. By default, we wait indefinitely. backlog: The TCP backlog argument. Defaults to 512. tcpkeepalive: A boolean value that controls if tcp keepalive is enabled for connections to servers. Defaults to false. preconnect: A boole