ZkOCaml

Apache zookeeper client binding for OCAML programming language.

ZkOCaml: an one-minute introduction for beginners

ZkOCaml is the first(as far as I know) Ocaml binding for Apache Zookeeper. If you are wondering what is Apache Zookeeper, please visit the zookeeper official website to get more information about it, hereinafter is an one-sentence description that can inform of you what is apache zookeeper:

ZooKeeper is a high-performance coordination service for distributed applications. It exposes common services - such as naming, configuration management, synchronization, and group services - in a simple interface so you don't have to write them from scratch. You can use it off-the-shelf to implement consensus, group management, leader election, and presence protocols.

ZkOCaml provides a complete API binding of Ocaml for apache zookeeper(hereinafter referred to as zookeeper), including synchronous and asynchronous interface as well as some useful auxiliary APIs. That is, you may create/delete/get/update(CRUD) a zookeeper node(ZNode) in Ocaml language synchronously and/or asynchronously without any pains.

How to build ZkOCaml

Prepare to build ZkOCaml

First of all, you have to get ZkOCaml source code from github:

~$git clone git@github.com:forhappy/zkocaml.git

Dependencies

ZkOCaml has no other dependencies except for zookeeper c API implementation, which usually resides in zookeeper-X.Y.Z/src/c, hence you need to install zookeeper c API at first.

Install ZkOCaml

all you have to do is just a make to compile ZkOCaml:

ZkOCaml$ make

If you want to install ZkOCaml into your system after you have compiled ZkOCaml, you need to make install(as root):

ZkOCaml$ make install

Getting started in 5 minutes

Examples

How to connect to zookeeper service

open Zookeeper

let watcher_fn zhandle event_type conn_state path watcher_ctx =
  if event_type = Zookeeper.ZOO_SESSION_EVENT then
    if conn_state = Zookeeper.ZOO_CONNECTED_STATE then
      print_string "Connected to zookeeper service successfully.\n"
    else if conn_state = Zookeeper.ZOO_EXPIRED_SESSION_STATE then
      print_string "Zookeeper session expired\n"

let zh = init "127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183" watcher_fn 3600 {client_id = 0L; passwd=""} "hello world" 0;;

read_line();;

How to create a node asynchronously

open Zookeeper

let acl = [|{perms = 0x1f; scheme = "auth"; id = ""}|]
let create_flag = Zookeeper.ZOO_SEQUENCE

let watcher_fn zhandle event_type conn_state path watcher_ctx =
  if event_type = Zookeeper.ZOO_SESSION_EVENT then
    if conn_state = Zookeeper.ZOO_CONNECTED_STATE then
      print_string "Connected to zookeeper service successfully.\n"
    else if conn_state = Zookeeper.ZOO_EXPIRED_SESSION_STATE then
      print_string "Zookeeper session expired\n"

let string_completion rc value data =
  if rc = Zookeeper.ZOK then
    print_string ("Create node Ok with returned value: " ^ value ^ "\n")
  else
    print_string "Failed to create node.\n"

let connect host = init host watcher_fn 3600 {client_id = 0L; passwd=""} "hello world" 0

let acreate_node handle path value = acreate handle path value acl Zookeeper.ZOO_SEQUENCE string_completion "(*acreate*)"

let handle = connect "127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183";;

read_line();;

let _ = acreate_node handle "/example" "hello";;

read_line();;

API specification

See docs/* and examples/* for more details about ZkOCaml's API specification.

License

Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.