https://github.com/membase/libvbucket

Utility library providing mapping to virtual buckets
https://github.com/membase/libvbucket

Last synced: 16 days ago
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Utility library providing mapping to virtual buckets

• Host: GitHub
• URL: https://github.com/membase/libvbucket
• Owner: membase
• License: apache-2.0
• Created: 2010-05-26T18:22:52.000Z (over 14 years ago)
• Default Branch: master
• Last Pushed: 2017-11-02T00:30:47.000Z (about 7 years ago)
• Last Synced: 2024-07-31T22:55:18.534Z (3 months ago)
• Language: C
• Homepage: http://www.membase.org/
• Size: 692 KB
• Stars: 52
• Watchers: 23
• Forks: 17
• Open Issues: 2
• Metadata Files:
  • Readme: README.markdown
  • License: LICENSE

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README

        
libvbucket: a vbucket library for memcached

===========================================

Config Syntax

-------------

libvbucket uses JSON for it's configuration format. The directory

`tests/config` contains sample configurations for [vbucket][1] and

[ketama][2] distribution algorithms taken from a live Couchbase

cluster.

Envelope Section

----------------

Configurations can have an optional envelope. If it is absent,

libvbucket will treat the config stream as a VBucket section.

### name

The username which should be used for nodes.  This will be used for both

authentication in HTTP and over memcached binary protocol.  Note that 

"default" is a special bucket which does not use HTTP auth or memcached

protocol auth.  Specifying "default" and empty string for password will

configure the client to use the default bucket.

    "name": "default",

### saslPassword

The password which should be used for nodes, which need authentication.

    "saslPassword": "",

### nodeLocator

The distribution algorithm which will be used to map keys to nodes. If this

field is absent the `vbucket` locator will be used. The possible values

are `ketama` and `vbucket`.

    "nodeLocator": "vbucket",

### vBucketServerMap

The section which describes the vbucket configuration. See the "VBucket

Section" below.

### nodes

The list of objects which describe the nodes in the cluster. The

parser will look for `couchApiBase`, `hostname` and `ports` fields in

this entry.

* hostname

  The hostname and port of the cluster's REST interface.

      "hostname": "172.16.16.76:8091",

* couchApiBase

  The endpoint for CouchDB REST interface. This endpoint should be used

  for Couch view execution.

      "couchApiBase": "http://172.16.16.76:8091/default",

* ports

  List of node ports. Currenty it contains `direct` and `proxy` port to

  connect to the node using memcached protocol. The proxy port could be

  used for vbucket unaware, legacy clients.

      "ports": {

        "proxy": 11211,

        "direct": 11210

      },

VBucket Section

---------------

The configuration string is JSON.

Example:

    {

      "hashAlgorithm": "CRC",

      "numReplicas": 2,

      "serverList": ["server1:11211", "server2:11210", "server3:11211"],

      "vBucketMap":

        [

          [0, 1, 2],

          [1, 2, 0],

          [2, 1, -1],

          [1, 2, 0]

        ]

    }

### hashAlgorithm

The hash algorithm can be in upper or lower case. libvbucket currently

uses a CRC32 hashing algorithm, a good general purpose hash for short

strings.  The hash algorithm will typically be ketama for memcached

type buckets.

### numReplicas

numReplicas is the number of extra copies that will be stored on

servers. Each vBucket in vBucketMap must have this number of server

indexes plus one (the master server).

### serverList

This has one string per server, in whatever format your app expects a

server config string in. This may change to be more structured later.

### vBucketMap

This contains one entry per vBucket, and the number of entries must be

a power of two. Each entry must be an array of `numReplicas+1`

zero-based indices into serverList, with the first entry indicating

the master server for the bucket and the remaining entries specifying

the replicas, in order. `-1` indicates that no server is mapped for that

particular master/replica of that particular vBucket.

Note there is also a vBucketMapForward which can be sent by the server

in the case that changes are occurring.  The vBucketMapForward indicates

what the future state of the cluster layout will be.

[1]: https://github.com/membase/libvbucket/blob/master/tests/config/vbucket-eight-nodes

[2]: https://github.com/membase/libvbucket/blob/master/tests/config/ketama-eight-nodes