a memcached proxy with energy and pep
sriganes and trondn MB-25403: Remove ep_version statistic
Change-Id: I405906fcda605394e51a006849c55911d5a08284
Reviewed-on: http://review.couchbase.org/81649
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Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
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           a memcached/membase proxy with energy and pep

What is it?

moxi is a proxy capable of handling many connections for client
applications, providing those clients simplified management and
increased performance.  It can be used with memcached servers or
a Membase Cluster hosting both membase and memcached type buckets.

For more information see http://membase.org


To have moxi load a "vBucket" json configuration from a REST/HTTP
server, try...

  moxi http://host:port/url/of/vBucketServerMapJSON

Against a NorthScale server, for example, this would look like...

  moxi http://host:8091/pools/default/bucketsStreamingConfig/default

The above, also, is just shorthand (assuming you have no other flags
specified), for the following explicit command-line...

  moxi -z url=http://host:8091/url/of/vBucketServerMap.json

To provide reliability when running with multiple servers, moxi will 
accept multiple URLs.  For example...

  moxi \ 

When used with particular buckets, authentication may be required.
This can be done with the additional arguments to the -z flag...

  moxi -z auth=USER%PASSWD,url=http://host:8091...

To get more command line usage info:

  moxi -h

  Keeping moxi Running

On UNIX and UNIX-like systems, moxi may be started with an external
service management system.  This will vary from system to system
but many have BSD or SysV style init systems.  Other, more advanced
service systems may be used too. 

  File-based configuration:

You may also provide a configuration file to moxi that holds a static
vBucket server map.  This is most often used during development and
testing.  The file (such as vbucket1.cfg) would look like...

  11211 = {
    "hashAlgorithm": "CRC",
    "numReplicas": 0,
    "serverList": ["memcached_svr1:11311"],

The above configuration would tell moxi to listen on port 11211, and
proxy to memcached_svr1:11311.  To use a static configuration file,
you would start moxi like...

  moxi -z ./vbucket1.cfg

The "./" path prefix is required so that moxi knows you're passing in
a config file.



   -- libevent, http://www.monkey.org/~provos/libevent/ (libevent-dev)

   -- libconflate, http://github.com/northscale/libconflate

   -- libvbucket, http://github.com/northscale/libvbucket

As a backwards-compatible (ketama/consistent-hashing) alternative to
libvbucket, you may instead use libmemcached instead of libvbucket...

   -- libmemcached, http://tangent.org/552/libmemcached.html

To use moxi against membase, however, you'll want libvbucket.

                     -   -   -

To compile moxi (assuming you want libvbucket), after you got the
dependencies built and installed:


For example, if libevent is installed in /opt/local, you'd do...

  ./configure --with-libevent=/opt/local


  # To test that moxi still behaves like memcached
  # and passes all the tests that memcached passes...
  make test

  # To test moxi in a simple proxy topology of...
  #  client <-> moxi <-> memcached

  # To test moxi in a chained proxy topology of...
  #   client <-> moxi <-> moxi <-> moxi <-> memcached
  ./t/moxi.pl chain

  # To test moxi in a fanout topology of...
  #   client <---> moxi <---> memcached
  #                       |-> memcached
  #                       |-> memcached
  #                       |-> memcached
  ./t/moxi.pl fanout

  # To test moxi in a fanout and back in again topology of...
  #   client <---> moxi <---> moxi <-> memcached
  #            |-> moxi <-|
  #            |-> moxi <-|
  #            |-> moxi <-|
  ./t/moxi.pl fanoutin

  # To test moxi proxy cases...
  ./moxi -z 11333=localhost:11311 -t 1
  python t/moxi_mock.py

                     -   -   -

For vbucket development, start the following...

  ruby ./t/rest_mock.rb

Then start a "pretend" memcached server...

  ./moxi -vvv -p 11311


  ./moxi -vvv -z url=http://localhost:4567/pools/default/bucketsStreaming/default -Z port_listen=11211


  telnet localhost 11211

                     -   -   -
More notes:

If using Linux, you need a kernel with epoll (it's better than select()).

epoll isn't in Linux 2.4 yet, but there's a backport at:


You want the epoll-lt patch (level-triggered).

If you're using MacOS, you'll want libevent 1.1 or higher to deal with
a kqueue bug.

Also, be warned that the -k (mlockall) option to memcached might be
dangerous when using a large cache.  Just make sure the memcached machines
don't swap.  memcached does non-blocking network I/O, but not disk.  (it
should never go to disk, or you've lost the whole point of it)

The memcached website is at:


                     -   -   -

Building moxi for use with libmemcached

If you want to use moxi explicitly using ketama / consistent-hashing,
instead of libvbucket with membase, you'll need to compile moxi with

First, you would configure moxi differently at build-time...

  ./configure --enable-moxi-vbucket=no \
     CFLAGS=<libmemcached/include> \

After building, moxi understands the following kind of command-line...

  moxi -z <port=<more-config>>

  moxi -z <port=<memcached_host:memcached_port(,*)>>

moxi will listen on the given port and accept connections from
upstream memcached clients.  It will forward requests to downstream
memcached servers running on memcached_host:memcached_port.  For

  moxi -z 11211=my_memcached_server:11222

Above, moxi will listen on port 11211 and forward requests
to the memcached running on my_memcached_server that's listening
on port 11222.

You can list more than one memcached_host:memcached_port,
separated by commas.  For example...

  moxi -z 11211=memcached_1:11211,memcached_2:11211

The default downstream port is 11211, so you can also
just use...

  moxi -z 11211=memcached_1,memcached_2

If you have some memcached servers running on the same server,
but on different ports, you can put moxi in front of them
with something like...

  moxi -z 11211=server:11222,server:11233