Name

lua-resty-kafka - Lua kafka client driver for the ngx_lua based on the cosocket API

Table of Contents

• Name
• Status
• Description
• Synopsis
• Modules
  • resty.kafka.client
    • Methods
      • new
      • fetch_metadata
      • refresh
  • resty.kafka.producer
    • Methods
      • new
      • send
      • offset
      • flush
• Installation
• TODO
• Author
• Copyright and License
• See Also

Status

This library is still under early development and is still experimental.

Description

This Lua library is a Kafka client driver for the ngx_lua nginx module:

http://wiki.nginx.org/HttpLuaModule

This Lua library takes advantage of ngx_lua's cosocket API, which ensures 100% nonblocking behavior.

Note that at least ngx_lua 0.9.3 or ngx_openresty 1.4.3.7 is required, and unfortunately only LuaJIT supported (--with-luajit).

Synopsis

    lua_package_path "/path/to/lua-resty-kafka/lib/?.lua;;";

    server {
        location /test {
            content_by_lua '
                local cjson = require "cjson"
                local client = require "resty.kafka.client"
                local producer = require "resty.kafka.producer"

                local broker_list = {
                    { host = "127.0.0.1", port = 9092 },
                }

                local key = "key"
                local message = "halo world"

                -- usually we do not use this library directly
                local cli = client:new(broker_list)
                local brokers, partitions = cli:fetch_metadata("test")
                if not brokers then
                    ngx.say("fetch_metadata failed, err:", partitions)
                end
                ngx.say("brokers: ", cjson.encode(brokers), "; partitions: ", cjson.encode(partitions))


                -- sync producer_type
                local p = producer:new(broker_list)

                local offset, err = p:send("test", key, message)
                if not offset then
                    ngx.say("send err:", err)
                    return
                end
                ngx.say("send success, offset: ", tonumber(offset))

                -- this is async producer_type and bp will be reused in the whole nginx worker
                local bp = producer:new(broker_list, { producer_type = "async" })

                local ok, err = bp:send("test", key, message)
                if not ok then
                    ngx.say("send err:", err)
                    return
                end

                ngx.say("send success, ok:", ok)
            ';
        }
    }

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Modules

resty.kafka.client

To load this module, just do this

    local client = require "resty.kafka.client"

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Methods

new

syntax: c = client:new(broker_list, client_config)

The broker_list is a list of broker, like the below

[
    {
        "host": "127.0.0.1",
        "port": 9092
    }
]

An optional client_config table can be specified. The following options are as follows:

client config

• socket_timeout

  Specifies the network timeout threshold in milliseconds. SHOULD lagrer than the request_timeout.

• keepalive_timeout

  Specifies the maximal idle timeout (in milliseconds) for the keepalive connection.

• keepalive_size

  Specifies the maximal number of connections allowed in the connection pool for per Nginx worker.

• refresh_interval

  Specifies the time to auto refresh the metadata in milliseconds. Then metadata will not auto refresh if is nil.

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fetch_metadata

syntax: brokers, partitions = c:fetch_metadata(topic)

In case of success, return the all brokers and partitions of the topic. In case of errors, returns nil with a string describing the error.

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refresh

syntax: brokers, partitions = c:refresh()

This will refresh the metadata of all topics which have been fetched by fetch_metadata. In case of success, return all brokers and all partitions of all topics. In case of errors, returns nil with a string describing the error.

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resty.kafka.producer

To load this module, just do this

    local producer = require "resty.kafka.producer"

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Methods

new

syntax: p = producer:new(broker_list, producer_config?, cluster_name?)

It's recommend to use async producer_type.

broker_list is the same as in client

An optional options table can be specified. The following options are as follows:

socket_timeout, keepalive_timeout, keepalive_size, refresh_interval are the same as in client_config

producer config, most like in http://kafka.apache.org/documentation.html#producerconfigs

• producer_type

  Specifies the producer.type. "async" or "sync"

• request_timeout

  Specifies the request.timeout.ms. Default 2000 ms

• required_acks

  Specifies the request.required.acks, SHOULD NOT be zero. Default 1.

• max_retry

  Specifies the message.send.max.retries. Default 3.

• retry_backoff

  Specifies the retry.backoff.ms. Default 100.

• partitioner

  Specifies the partitioner that choose partition from key and partition num. syntax: partitioner = function (key, partition_num, correlation_id) end, the correlation_id is an auto increment id in producer. Default partitioner is:

• api_version

  Specifies the produce API version. Default 2. This requires Kafka server 0.10 or above. If you use Kafka 0.9.x, api_version should be 0 or 1. If you use Kafka 0.8.x, api_version should be 0.

local function default_partitioner(key, num, correlation_id)
    local id = key and crc32(key) or correlation_id

    -- partition_id is continuous and start from 0
    return id % num
end

buffer config ( only work producer_type = "async" )

• flush_time

  Specifies the queue.buffering.max.ms. Default 1000.

• batch_num

  Specifies the batch.num.messages. Default 200.

• batch_size

  Specifies the send.buffer.bytes. Default 1M(may reach 2M). Be careful, SHOULD be smaller than the socket.request.max.bytes / 2 - 10k config in kafka server.

• max_buffering

  Specifies the queue.buffering.max.messages. Default 50,000.

• error_handle

  Specifies the error handle, handle data when buffer send to kafka error. syntax: error_handle = function (topic, partition_id, message_queue, index, err, retryable) end, the failed messages in the message_queue is like { key1, msg1, key2, msg2 } , key in the message_queue is empty string "" even if orign is nil. index is the message_queue length, should not use #message_queue. when retryable is true that means kafka server surely not committed this messages, you can safely retry to send; and else means maybe, recommend to log to somewhere.

Not support compression now.

The third optional cluster_name specifies the name of the cluster, default 1 (yeah, it's number). You can Specifies different names when you have two or more kafka clusters. And this only works with async producer_type.

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send

syntax: ok, err = p:send(topic, key, message)

1. In sync model

   In case of success, returns the offset (** cdata: LL **) of the current broker and partition. In case of errors, returns nil with a string describing the error.

2. In async model

   The message will write to the buffer first. It will send to the kafka server when the buffer exceed the batch_num, or every flush_time flush the buffer.

   It case of success, returns true. In case of errors, returns nil with a string describing the error (buffer overflow).

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offset

syntax: sum, details = p:offset()

Return the sum of all the topic-partition offset (return by the ProduceRequest api);
and the details of each topic-partition

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flush

syntax: ok = p:flush()

Always return true.

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Installation

You need to configure the lua_package_path directive to add the path of your lua-resty-kafka source tree to ngx_lua's LUA_PATH search path, as in

    # nginx.conf
    http {
        lua_package_path "/path/to/lua-resty-kafka/lib/?.lua;;";
        ...
    }

Ensure that the system account running your Nginx ''worker'' proceses have enough permission to read the .lua file.

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TODO

1. Fetch API
2. Offset API
3. Offset Commit/Fetch API

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Author

Dejiang Zhu (doujiang24) doujiang24@gmail.com.

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Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2014-2014, by Dejiang Zhu (doujiang24) doujiang24@gmail.com.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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See Also

• the ngx_lua module: http://wiki.nginx.org/HttpLuaModule
• the kafka protocol: https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol
• the lua-resty-redis library
• the lua-resty-logger-socket library
• the sarama

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