Pandatech.SharedKernel 1.0.0

Pandatech.SharedKernel

Welcome to the Pandatech.SharedKernel NuGet package - a centralized library designed to streamline development across all PandaTech projects. This package consolidates shared configurations, utilities, and extensions into a single, reusable resource.

Although this package is primarily intended for internal use, it is publicly available for anyone who may find it useful. We recommend forking or copying the classes in this repository and creating your own package to suit your needs.

By leveraging this shared kernel, we aim to:

• Reduce the amount of boilerplate code required to start a new project.
• Ensure consistency across all PandaTech projects.
• Simplify the process of updating shared configurations and utilities.

Scope

This package currently supports:

• OpenAPI Configuration with SwaggerUI and Scalar.
• Logging with Serilog.
• MediatR and FluentValidation configurations.
• Cors Configuration with easy configuration options.
• Resilience Pipelines for HttpClient operations.
• Controller Extensions for mapping old-style MVC controllers.
• OpenTelemetry Integration for tracking metrics, traces, and logging.
• Health Checks with default endpoints and startup validation.
• Various Extensions and Utilities, including enumerable, string, and queryable extensions.

Prerequisites

• .NET 9.0 SDK or higher

Installation

To install the Pandatech.SharedKernel package, use the following command:

dotnet add package Pandatech.SharedKernel

Alternatively, you can add it via the NuGet Package Manager in Visual Studio, VS Code or Rider.

Full SharedKernel Demo

This section demonstrates how to use the Pandatech.SharedKernel package in a fully functional application. It includes examples of:

• Comprehensive appsettings.json configurations.
• Environment-specific settings in appsettings.{Environment}.json.
• A complete Program.cs implementation with all major features integrated.

Follow this example to set up your project with all the features provided by this library.

appsettings.json

{
    "OpenApi": {
        "DisabledEnvironments": [
            "Production"
        ],
        "SecuritySchemes": [
            {
                "HeaderName": "Client-Type",
                "Description": "Specifies the client type, e.g., '2'."
            },
            {
                "HeaderName": "Authorization",
                "Description": "Access token for the API."
            }
        ],
        "Documents": [
            {
                "Title": "Administrative Panel Partners",
                "Description": "This document describes the API endpoints for the Administrative Panel Partners.",
                "GroupName": "admin-v1",
                "Version": "v1",
                "ForExternalUse": false
            },
            {
                "Title": "Integration",
                "Description": "Integration API Endpoints",
                "GroupName": "integration-v1",
                "Version": "v1",
                "ForExternalUse": true
            }
        ],
        "Contact": {
            "Name": "Pandatech",
            "Url": "https://pandatech.it",
            "Email": "info@pandatech.it"
        }
    },
    "SwaggerUi": {
        "InjectedCssPaths": [
            "/assets/css/panda-style.css"
        ],
        "InjectedJsPaths": [
            "/assets/js/docs.js"
        ]
    },
    "ScalarUi": {
        "FaviconPath": "/assets/images/favicon.svg"
    }
}

appsettings.{Environment}.json

{
    "Serilog": {
        "MinimumLevel": {
            "Default": "Information",
            "Override": {
                "Microsoft": "Information",
                "System": "Information"
            }
        }
    },
    "RepositoryName": "be-lib-sharedkernel",
    "ConnectionStrings": {
        "PersistentStorage": "/persistence"
    },
    "Security": {
        "AllowedCorsOrigins": "https://example.com,https://api.example.com"
    }
}

Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.LogStartAttempt();
AssemblyRegistry.Add(typeof(Program).Assembly);

builder
   .AddPandaVault()
   .AddSerilog()
   .AddResponseCrafter(NamingConvention.ToSnakeCase)
   .AddOpenApi()
   .AddOpenTelemetry()
   .AddEndpoints(AssemblyRegistry.ToArray())
   .AddControllers(AssemblyRegistry.ToArray())
   .AddMediatrWithBehaviors(AssemblyRegistry.ToArray())
   .AddResilienceDefaultPipeline()
   .MapDefaultTimeZone()
   .AddCors();

builder.Services.AddHealthChecks();


var app = builder.Build();

app
   .UseRequestResponseLogging()
   .UseResponseCrafter()
   .UseCors()
   .MapEndpoints()
   .MapDefaultEndpoints()
   .EnsureHealthy()
   .ClearAssemblyRegistry()
   .UseOpenApi();

app.LogStartSuccess();
app.Run();

For a deeper dive into each feature, please refer to the following sections.

OpenAPI

Microsoft.AspNetCore.OpenApi is the new standard for creating OpenAPI JSON files. We have adopted this library instead of Swashbuckle for generating OpenAPI definitions. Along with this new library, we have integrated SwaggerUI and Scalar to provide user-friendly interfaces in addition to the JSON files.

Key Features

• Multiple API Documents: Easily define and organize multiple API documentation groups.
• Enum String Values: Enum string values are automatically displayed in the documentation, simplifying integration for external partners.
• Customizable SwaggerUI: Add custom styles and JavaScript to tailor the UI.
• Security Schemes: Configure security headers directly in your OpenAPI settings.

Adding OpenAPI to Your Project

To enable OpenAPI in your project, add the following code:

var builder = WebApplication.CreateBuilder(args);
builder.AddOpenApi();
var app = builder.Build();
app.UseOpenApi();
app.Run();

You can also customize the AddOpenApi method with options:

builder.AddOpenApi(options =>
{
    options.AddSchemaTransformer<CustomSchemaTransformer>();
});

Configuration

Add the following configuration to your appsettings.json file:

{
    "OpenApi": {
        "DisabledEnvironments": [
            "Production"
        ],
        "SecuritySchemes": [
            {
                "HeaderName": "Authorization",
                "Description": "Access token for the API."
            }
        ],
        "Documents": [
            {
                "Title": "Admin Panel API",
                "Description": "API for administrative functions.",
                "GroupName": "admin-v1",
                "Version": "v1",
                "ForExternalUse": false
            },
            {
                "Title": "Integration",
                "Description": "Integration API Endpoints",
                "GroupName": "integration-v1",
                "Version": "v1",
                "ForExternalUse": true
            }
        ],
        "Contact": {
            "Name": "Pandatech",
            "Url": "https://pandatech.it",
            "Email": "info@pandatech.it"
        }
    },
    "SwaggerUi": {
        "InjectedCssPaths": [
            "/assets/css/panda-style.css"
        ],
        "InjectedJsPaths": [
            "/assets/js/docs.js"
        ]
    },
    "ScalarUi": {
        "FaviconPath": "/assets/images/favicon.svg"
    }
}

Notes

• For External Use: If you set ForExternalUse: true for a document, it will be available both within the regular SwaggerUI and a separate SwaggerUI instance. This allows you to provide a dedicated URL to external partners while keeping internal documents private.
• Scalar UI Limitations: Scalar currently does not support multiple documents within a single URL. Consequently, all documents in Scalar will be separated into individual URLs. Support for multiple documents is expected in future Scalar updates.

Example URLs

Based on the above configuration, the UI will be accessible at the following URLs:

• Swagger (all documents): http://localhost/swagger
• Swagger (external document only): http://localhost/doc/integration-v1
• Scalar (admin document): http://localhost/scalar/admin-v1
• Scalar (integration document): http://localhost/scalar/integration-v1

Logging

Key Features

• Serilog Integration: Simplified setup for structured logging using Serilog.
• Environment-Specific Configuration: Logs are written to the console and/or files based on the environment (Local, Development, Production).
• Elastic Common Schema Formatting: Logs are formatted using the Elastic Common Schema (ECS) for compatibility with Elasticsearch.
• Request and Response Logging Middleware: Middleware that logs incoming requests and outgoing responses while redacting sensitive information.
• Log Filtering: Excludes unwanted logs from Hangfire Dashboard, Swagger, and outbox database commands.
• Distributed: Designed to work with distributed systems and microservices.

Adding Logging to Your Project

To enable Serilog logging in your project, add the following code:

var builder = WebApplication.CreateBuilder(args);
builder.AddSerilog();

In your middleware pipeline, add the request and response logging middleware:

var app = builder.Build();
app.UseRequestResponseLogging();

In your appsettings.{Environment}.json configure Serilog. Example:

{
    "Serilog": {
        "MinimumLevel": {
            "Default": "Information",
            "Override": {
                "Microsoft": "Information",
                "System": "Information"
            }
        }
    },
    "RepositoryName": "be-lib-sharedkernel",
    "ConnectionStrings": {
        "PersistentStorage": "/persistence"
    }
}

Work Specifics

• Environment-Specific Logging:
  • Local Environment: Logs are written to the console.
  • Production: Logs are written to a file.
  • Other Environments: Logs are written to both the console and a file.
• Log File Location: Logs are stored in a persistent path defined in your configuration, organized by repository name and environment.
• Sensitive Data Redaction: The middleware automatically redacts sensitive information such as passwords, secrets, tokens, and authentication details from headers and bodies.

Startup Logging

The package provides methods to log application startup events:

• LogStartAttempt(): Logs when the application start is attempted.
• LogStartSuccess(): Logs when the application has successfully started, including the initialization time.
• LogModuleRegistrationSuccess(moduleName): Logs successful registration of a module.
• LogModuleUseSuccess(moduleName): Logs successful usage of a module.

Example:

var builder = WebApplication.CreateBuilder(args);
builder.LogStartAttempt();
// Configure services
var app = builder.Build();
// Configure middleware
app.UseRequestResponseLogging();
// Other middleware
app.LogStartSuccess();
app.Run();

MediatR and FluentValidation Integration

Key Features

• MediatR Integration: Simplifies the implementation of the Mediator pattern for handling commands and queries.
• Custom Interfaces for CQRS: Provides ICommand and IQuery interfaces to facilitate the Command Query Responsibility Segregation (CQRS) pattern.
• Validation Behaviors: Automatically validates requests using FluentValidation before they reach the handler.
• FluentValidation Extensions: Includes custom validators for common scenarios like file size, file type, JSON validity, and XSS sanitization.

Adding MediatR to Your Project

To enable MediatR with validation behaviors in your project, add the following code:

var builder = WebApplication.CreateBuilder(args);
builder.AddMediatrWithBehaviors([typeof(Program).Assembly]);

This extension method registers MediatR and adds custom pipeline behaviors for validation. It scans the specified assemblies for handlers and validators.

How It Works

Custom Interfaces for CQRS The package provides custom interfaces to distinguish between commands and queries, aligning with the CQRS pattern:

• Commands:
  • ICommand<TResponse> and ICommand
  • Handled by ICommandHandler<TCommand, TResponse> and ICommandHandler<TCommand>
• Queries:
  • IQuery<TResponse> and IQuery
  • Handled by IQueryHandler<TQuery, TResponse> and IQueryHandler<TQuery>

These interfaces help in organizing your application logic and can be extended in the future, for example, to route read requests to replicas and write requests to a primary database.

Validation Behaviors

Two custom pipeline behaviors are added to MediatR:

• ValidationBehaviorWithResponse<TRequest, TResponse>: Used for requests that expect a response.
• ValidationBehaviorWithoutResponse<TRequest, TResponse>: Used for requests that do not expect a response.

These behaviors automatically validate the incoming requests using FluentValidation validators before they reach the handler. If validation fails, a BadRequestException is thrown with the validation errors.

BadRequestException is from Pandatech.ResponseCrafter NuGet package

FluentValidation Extensions

The package includes extension methods to simplify common validation scenarios:

• File Validations:
  • HasMaxFileSize(maxFileSizeInMb): Validates that an uploaded file does not exceed the specified maximum size.
    • FileTypeIsOneOf(allowedFileExtensions): Validates that the uploaded file has one of the allowed file extensions.
• String Validations:
  • IsValidJson(): Validates that a string is a valid JSON.
    • IsXssSanitized(): Validates that a string is sanitized against XSS attacks.

Cors

Key Features

• Non-Production Environment: Allows all origins for ease of development and testing.
• Production Environment
  • Restricts origins to a specific list defined in the configurations.
  • Automatically handles www and non-www versions of allowed origins.
  • Supports credentials, all methods and headers, and preflight caching.

Adding Cors to Your Project

To enable Cors in your project, add the following code:

var builder = WebApplication.CreateBuilder(args);
builder.AddCors();
var app = builder.Build();
app.UseCors();
app.Run();

Configuration

Add following to your appsetings.production.json file:

{
    "Security": {
        "AllowedCorsOrigins": "https://example.com,https://api.example.com"
    }
}

• AllowedCorsOrigins: A comma- or semicolon-separated list of allowed origins. Invalid URLs are automatically filtered out.

Resilience Pipelines

Key Features

• Default Resilience Pipeline: Provides a pre-configured resilience pipeline with retry, circuit breaker, and timeout policies.
• Polly Integration: Utilizes the Microsoft.Extensions.Http.Resilience library which is built on Polly library for implementing advanced resilience strategies.
• Flexible Configuration: Can be applied globally via WebApplicationBuilder or locally within specific HTTP client configurations.
• HTTP Client Resilience: Enhances the reliability of HTTP client calls by handling transient faults and network issues.

Adding Resilience Pipelines to Your Project

To enable the default resilience pipeline in your project, you have 3 options:

1. Global Configuration via WebApplicationBuilder This method applies the resilience pipeline to all HTTP clients registered in your application.

   var builder = WebApplication.CreateBuilder(args);
   builder.AddResilienceDefaultPipeline();
   

2. Local Configuration within HTTP Client Registration This method applies the resilience pipeline to a specific HTTP client registration.

   builder.Services.AddHttpClient("MyHttpClient")
    .AddResilienceDefaultPipeline();
   

3. Configuration within HttpClientService.cs

   public class MyHttpClientService
   {
   private readonly ResiliencePipelineProvider<string> _resiliencePipelineProvider;
   private readonly HttpClient _httpClient;
   
       public MyHttpClientService(ResiliencePipelineProvider<string> resiliencePipelineProvider, HttpClient httpClient)
       {
           _resiliencePipelineProvider = resiliencePipelineProvider;
           _httpClient = httpClient;
       }
   
       public async Task FooAsync()
       {
           var pipeline = _resiliencePipelineProvider.GetDefaultPipeline();
           var response = await pipeline.ExecuteAsync(() => _httpClient.GetAsync("https://example.com"));
       }
   }
   

How It Works

The default resilience pipeline includes the following policies:

• Retry Policy for 429 (Too Many Requests): Retries the request up to 5 times with an exponential backoff, respecting the Retry-After header if present.
• Retry Policy for Network Errors and Timeouts: Retries network-related failures up to 7 times with an exponential backoff.
• Circuit Breaker Policy: Breaks the circuit when the failure ratio exceeds 50% within a 30-second sampling duration, with a minimum throughput of 200 requests.
• Timeout Policy: Times out requests that take longer than 8 seconds.

Controller Extensions

For mapping old style MVC controllers, use builder.AddControllers(). The AddControllers() method can also accept assembly names as parameters to scan for controllers.

Example:

builder.AddControllers([typeof(Program).Assembly]);

OpenTelemetry

Use builder.AddOpenTelemetry() to add OpenTelemetry to your project. This will track metrics, traces, and logging at runtime, including ASP.NET Core and HttpClient operations.

Example:

var builder = WebApplication.CreateBuilder(args);
builder.AddOpenTelemetry();

HealthChecks

The app.EnsureHealthy() extension method performs a health check at startup and will terminate the application if it is not healthy.

Example:

var app = builder.Build();
app.EnsureHealthy();

Default Endpoints

To map default endpoints, use app.MapDefaultEndpoints(). This will add the following endpoints:

• Ping Endpoint: url/above-board/ping
• Health Check Endpoint: url/above-board/health
• Prometheus Metrics Endpoint: url/above-board/metrics
• Prometheus Health Metrics Endpoint: url/above-board/metrics/health

Note: To use Prometheus endpoints, you need to apply OpenTelemetry as well.

Example:

app.MapDefaultEndpoints();

Additional Extensions and NuGet Packages

This package includes various extensions and utilities to aid development:

• Enumerable Extensions: Additional LINQ methods for collections.
• Host Environment Extensions: Methods to simplify environment checks (e.g., IsLocal(), IsQa()).
• Queryable Extensions: Extensions for IQueryable, such as conditional WhereIf.
• String Extensions: Utility methods for string manipulation.
• Time Zone Extensions: Methods to handle default time zones within your application. Use .MapDefaultTimeZone(), which retrieves DefaultTimeZone from appsettings.json and sets it as the default time zone.
• UrlBuilder: A utility for building URLs with query parameters.

Related NuGet Packages

• Pandatech.Crypto: Provides cryptographic utilities.
• Pandatech.FluentMinimalApiMapper: Simplifies mapping in minimal APIs.
• Pandatech.RegexBox: A collection of useful regular expressions.
• Pandatech.ResponseCrafter: A utility for crafting consistent API responses.

License

MIT License