gouptime

README

GoUptime

Table of Contents

• About
• Contributing
  • DataSource
  • Handlers
• Flow
• Prerequisites

About

GoUptime lets you verify if your favorites page are Up and notify you if there are something wrong with them!

Contributing

We are using a Priority Queue to handle a pages list with their respective priority. You can see the implementation right here.

The UptimeChecker structure (here) is your tools to check each page and do something with the result of. It use the PriorityQueue type to iterate over all pages ordered by their priority (descending order). On each iterate, it just do a HTTP GET Request against the URL provided and execute a method passing the URL, HTTP Status Code, HTTP Status Message and and sync.WaitGroup. The WaitGroup is used to communicate to the main thread that all pages were handled since we're using go routines.

In essence, the project is extensible. For that we created two interfaces: DataSource and Handlers, here and here respective.

DataSource

This interface MUST be implemented if you want to create your own way to populate a list of pages. This interface only need to implement a single "method": Dispatch that receive a map[string]HandlerFunc (hash list of handlers functions as value with their identifers as key) and returns a pointer to a PriorityQueue. The source of your data runs by your own. Whatever your data source are, you MUST give a list of: page URL, priority and a handler identifer, e.g:

[
    ["www.google.com", 100, "LOG"],
    ["www.alibaba.com", 20, "DISCORD"],
    ...
]

You will need to use the Page struct and the Node struct to construct your PriorityQueue. There is a built-in called CSVDataSource (here). It can help you to get familiarized.

NOTE: You have an sample CSV here

Handlers

This interface MUST be implemented if you want to create your own way to handle the result of the UptimeChecker. In each iteration, UptimeChecker will call the HandlerFunc associated with the target page. You only need to implement the Dispatch method, receiving the Page URL, HTTP Status Code, HTTP Status Message and and pointer to a sync.WaitGroup. The first thing that you need to do is declare a defer to the Done method of the WaitGroup. This is MANDATORY. No exceptions. If you don't do that, the process will freeze until you force their exit.

Handlers let you do something with the result of the request against the target page, e.g., send email notification, send WhatsApp message, Discord message, etc. There are three handlers built-in: StdOutHandler (useful for testing), LoggerHandler (write to a log file) and DiscordHandler (send message to a Discord channel), here, here and here respective.

Each handler MUST be registered in the main function. The RegisterHandler method of Handlers struct will do the work. You job is to give to you function an unique identifer as key and a pointer to your HandlerFunc as value. You can see the main file to see how that work.

Flow

We use gocron to make a unix CRON like behavior. So, the first step in main function is register all of the HandlerFuncs available. Then, we create a time frequency for our UptimeChecker, which is defined with the interval flag on command invocation. On each call, we initialize our UptimeChecker with the Init method, passing our DataSource and our Handlers as arguments. Next, the VerifyStatus method is executed, which iterate over our populated pages and executing their HandlerFunc.

Prerequisites

• Golang (tested on go1.16.6 linux/amd64)

Usage

To use with the CSVDataSource you need to set an environment var called CSV_PATH which contain the absolute path of the CSV file containing your populated pages with the format url,priority,handler (same as the CSV sample in this repo).

To use the Discord handler, you need to set two environment vars: DISCORD_BOT_TOKEN and DISCORD_CHANNEL_ID. Self explanatory.

You MUST pass interval flag to define the time interval to execute the job. The syntax is similar to UNIX CRON, but is enhanced by robfig/cron package. Please, see that doc to see features available.

$ CSV_PATH=$HOME/pages.csv DISCORD_BOT_TOKEN=XXX DISCORD_CHANNEL_ID=XXX ./gouptime -interval "@every 5m"

Examples for interval flag

• @every <interval> "interval" is a valid value for time.ParseDuration
• */5 * * * * * Every five seconds. Note that there is a extra value to the standard UNIX CRON entry. The first values define seconds intervals
• @daily Once a day or midnight
• @every 1h30 Every on hour thirty