Telegram HealthCheck

REST web application that provides health check functionality with output to Telegram messenger

Before note:

This application was designed in mind as a fully free hosted service for Azure cloud.

Requirements:

• Azure Cosmos DB account
• Azure App Service plan
• Azure App Service
• Telegram bot

Setup:

Azure:

1. Create dedicated resource group
2. Create required resources manually or using included templates

To host this application completely for free insure that you are using next settings to achieve that:

• All: Use the same region across all resources
• Azure Cosmos DB account: Use Free Tier Discount
• Azure App Service plan: Use F1 tier with Linux containers

Telegram:

This documentation will not cover any setup for Telegram messenger, but the process are straight forward.

Application configuration:

One application instance can have multiple health check endpoints. All endpoints are validated using HTTP GET method.

It's NOT RECOMMENDED to use UpdateEach value less than 2 minutes (0.00:02:00) because default value for HttpClient.Timeout are 100 seconds. Otherwise this could cause HTTP requests to be queued with afterwards delays, exceptions or application crashes.

Configuration for application can be changed in application settings file or using environmental variables. There are examples how to configure application:

1. Application settings file:

"CosmosDbConfiguration": {
  "ConnectionString": "AccountEndpoint=[AccountEndpoint];AccountKey=[AccountKey];"
},
"HealthCheckConfiguration": [
  {
    "Id": "Azure",
    "Url": "https://portal.azure.com",
    "UpdateEach": "0.00:02:00",
    "TelegramChatId": "[TelegramChatId]",
    "TelegramBotApiKey": "[TelegramBotApiKey]",
    "MessageWhenSucceeded": "🟢 Connection restored",
    "MessageWhenFailed": "🔴 Connection lost because {StatusText} ({StatusCode})"
  },
  {
    "Id": "Google",
    "Url": "https://google.com",
    "UpdateEach": "0.00:05:00",
    "TelegramChatId": "[TelegramChatId]",
    "TelegramBotApiKey": "[TelegramBotApiKey]",
    "MessageWhenSucceeded": "🟢 Connection restored",
    "MessageWhenFailed": "🔴 Connection lost because {StatusText} ({StatusCode})"
  }
]

2. Enviromental variables:

"CosmosDbConfiguration__ConnectionString": "AccountEndpoint=[AccountEndpoint];AccountKey=[AccountKey];"
"HealthCheckConfiguration__0__Id": "Azure"
"HealthCheckConfiguration__0__Url": "https://portal.azure.com"
"HealthCheckConfiguration__0__UpdateEach": "0.00:02:00"
"HealthCheckConfiguration__0__TelegramChatId": "[TelegramChatId]"
"HealthCheckConfiguration__0__TelegramBotApiKey": "[TelegramBotApiKey]"
"HealthCheckConfiguration__0__MessageWhenSucceeded": "🟢 Connection restored"
"HealthCheckConfiguration__0__MessageWhenFailed": "🔴 Connection lost because {StatusText} ({StatusCode})"
"HealthCheckConfiguration__1__Id": "Google"
"HealthCheckConfiguration__1__Url": "https://google.com"
"HealthCheckConfiguration__1__UpdateEach": "0.00:05:00"
"HealthCheckConfiguration__1__TelegramChatId": "[TelegramChatId]"
"HealthCheckConfiguration__1__TelegramBotApiKey": "[TelegramBotApiKey]"
"HealthCheckConfiguration__1__MessageWhenSucceeded": "🟢 Connection restored"
"HealthCheckConfiguration__1__MessageWhenFailed": "🔴 Connection lost because {StatusText} ({StatusCode})"