lua-resty-pubsub

Lua Pubsub client driver for the ngx_lua based on the cosocket API.

Table of Contents

• Description
• Synopsis
• Configs
• Modules
  • resty.pubsub.producer
    • Methods
      • new
      • send
• Dependencies
• Installation
• TODO
• Author
• Copyright and License
• See Also

Description

This Lua library is a Pubsub 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. This library pushes messages (with attributes) to Google Cloud pubsub using nginx timers and http requests.

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-pubsub/lib/?.lua;;";

    server {
        location = /publish {
            resolver 8.8.8.8 ipv6=off;

            content_by_lua_block {
                local cjson = require "cjson"
                local pubsub_producer = require "resty.pubsub.producer"
                local OAUTH_TOKEN = ngx.shared.OAUTH_TOKEN -- A different dictionary can also be provided

                -- A callback which will recieve messages if gets successfully sent
                -- Types of messages & err are a table
                local success_callback = function (topic, err, messages)
                    ngx.log(ngx.INFO, "Messages: ", cjson.encode(messages), " successfully pushed to topic: ", topic)
                end

                -- A callback which will recieve messages if gets failed
                -- Types of messages & err are a table
                local error_callback = function (topic, err, messages)
                    for _, message in ipairs(messages) do
                        ngx.log(ngx.ERR, "Failed to send Message : ", cjson.encode(message), " with err: ", cjson.encode(err))
                    end
                end

                local publish = function()

                    -- Pubsub Producer Config
                    local pubsub_config = {
                        project_id = "demo-project",
                        topic = "demo-topic",
                        pubsub_base_domain = "pubsub.googleapis.com",
                        pubsub_base_port = 443,
                        is_emulator = false,
                        producer_config = {
                            max_batch_size = 200, -- number of packets
                            max_buffering = 5000, -- max number of packets in buffer
                            timer_interval = 10000, -- in milliseconds
                            last_flush_interval = 5000, -- in milliseconds
                            http_timeout = 6000, -- in milliseconds
                            keepalive_max_idle_timeout = 2000, -- in milliseconds
                            keepalive_pool_size = 50
                        },
                        oauth_config = {
                            service_account_key_path = "/etc/key.json", -- Replace this with your own key path
                            oauth_base_uri = "https://www.googleapis.com/oauth2/v4/token",
                            oauth_scopes = {
                                "https://www.googleapis.com/auth/pubsub"
                            },
                            oauth_token_dict = OAUTH_TOKEN
                        },
                        success_callback = success_callback,
                        error_callback = error_callback
                    }

                    -- Create the producer object
                    -- No matter how many times you call new, the producer instance will always be generated once per topic per worker process
                    local producer, err = pubsub_producer:new(pubsub_config)

                    -- Also check if there is any error while initializing producer
                    if err ~= nil then
                        ngx.log(ngx.ERR, "Unable to create pubsub producer ", err)
                        return
                    end

                    -- Finally send the message with attributes.
                    local ok, send_err = producer:send("Some Random Text", {
                        attr1 = "Test1",
                        attr2 = "Test2"
                    }, "optional_ordering_key")

                    -- Also check if there is any error while sending message
                    if send_err ~= nil then
                        ngx.log(ngx.ERR, "Unable to send data to pubsub: ", send_err)
                        return
                    end

                end

                -- Publish Message
                publish()
            }

        }
    }

Configs

Producer Configs

Property	Data Type	Description	Default Value
project_id	string	Specifies the project id as a string of your Pub/Sub project	none (Required)
topic	string	Specifies the topic in which the data needs to be send	none (Required)
pubsub_base_domain	string	Specifies the base domain through which the http connection is made.	pubsub.googleapis.com
pubsub_base_port	number	Specifies the base domain port through which the http connection is made.	443
is_emulator	boolean	Specifies a boolean value. true if you are communicating with.	false
producer_config.max_batch_size	number	Specifies the max batch size that will be pushed to pubsub.	200
producer_config.max_buffering	number	Specifies the max size of the buffer which will hold the data for a specific duration of time.	5000
producer_config.timer_interval	number (milliseconds)	Specifies the time interval in which the stale messages in buffer are checked for publishing.	10000
producer_config.last_flush_interval	number (milliseconds)	Specifies the max interval between the last flush time and current time. Used when packets in buffer are less than the batch size for a longer period of time.	10000
producer_config.http_timeout	number (milliseconds)	Sets the timeout protection for subsequent operations, including the connect method.	5000
producer_config.keepalive_max_idle_timeout	number (milliseconds)	Used in httpc:set_keepalive which attempts to puts the current connection into the ngx_lua cosocket connection pool.	2000
producer_config.keepalive_pool_size	number	Used in httpc:set_keepalive which attempts to puts the current connection into the ngx_lua cosocket connection pool.	50
oauth_config.service_account_key_path	string	Specifies the path for service account key that are used to authenticate to pub/sub project.	none (Required)
oauth_config.oauth_base_uri	string	Specifies the base uri to which request is made to Google authorization server for a token that will be used in subsequent requests.	https://www.googleapis.com/oauth2/v4/token
oauth_config.oauth_scopes	list of string	Specifies a table comprising of OAuth 2.0 scopes that you might need to request to access Google APIs, depending on the level of access you need.	{"https://www.googleapis.com/auth/pubsub"}
oauth_config.oauth_token_dict	lua_shared_dict	Specifies a shared memory zone across workers, to serve as a storage for the oauth token.	ngx.shared.OAUTH_TOKEN
success_handler	function	This is a callback function which will be provided with all the messages with their attributes which are successfully pushed to pubsub.	none (Optional)
error_handler	function	This is a callback function which will be executed when a batch fails.	none (Optional)

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Modules

resty.pubsub.producer

To load this module, just do this

    local producer = require "resty.pubsub.producer"

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Methods

new

syntax: local p, err = producer:new(pubsub_config)

send

syntax: p:send(message, attributes[, ordering_key])

• Requires a message of type string, attributes of type table and an optional ordering_key of type string

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Dependencies

Lua modules required to build this library are:

• lua-cjson library
• lua-resty-rsa library
• lua-resty-http library

Installation

For Installing module

Method 1 - Using luarocks

For installing luarocks refer this

You can simply run luarocks install lua-resty-pubsub for installing this library

Method 2 - Using Makefile

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

    # nginx.conf
    http {
        ..
        lua_shared_dict     OAUTH_TOKEN 1m; # Replace OAUTH_TOKEN with the name you mentioned in `oauth_token_dict`
        ..
        lua_package_path "/path/to/lua-resty-pubsub/lib/?.lua;;";
        ...
    }

You also need to add google resolver so as to connect with pubsub endpoints

    # default.conf
    server {
        location = /test {
            resolver 8.8.8.8 ipv6=off;
            ...
	    }
    }

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

Also if using OAUTH_TOKEN dictionary, add lua_shared_dict in nginx.conf

Finally run make install for installing the module

For Running Test Cases

Install Test::Nginx module for running test cases

Finally run make test for running the test cases

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TODO

1. Pubsub Message Fetch API
2. Add Unit Test Cases

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Author

Vasu Gupta (vasu7052) https://github.com/Vasu7052.

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Copyright and License

The MIT License (MIT)

Copyright (c) 2020 Wingify Software Pvt. Ltd.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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See Also

• the ngx_lua module: http://wiki.nginx.org/HttpLuaModule

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