Bank API 🏦

The Bank API is a design reference project suitable to bootstrap development for a compliant and modern API.

Compliance

The API complies to:

✅ OWASP API Security Top 10 - v2023 via Spectral OWASP API Security ruleset

✅ OpenAPI Specification v3.0.1 via Spectral "oas" ruleset

✅ Additional naming conventions, structure, and clarity via Bank API project ruleset

✅ California Consumer Privacy Act (CCPA) and General Data Protection Regulation (GDPR) via ASP.Net Core Compliance

Technology stack

• ASP.NET Core 9.0 - Minimal API for API development, with following base services:

  • Resilience for resilience when calling downstream APIs

  • Compliance for redacting sensitive data

  • Health checks for checking health status

  • Service Discovery for resolving endpoints from config

  • Hybrid Cache for caching

  • Rate limiting for rate limiting

  • API Key, JWT bearer and OpenID Connection-based authentication for security

  • OpenApi for generating OpenAPI specifications

  • Cross-Origin Resource Sharing (CORS) for cross-origin requests

• OpenTelemetry (OTel) for observability

• .NET Aspire for development bootstrapping and client integrations

• Kiota API client generation for calling downstream APIs

• Gridify for filtering, ordering and paging

• Scalar for interactive API documentation

• Spectral for linting

• OpenApiAnyFactory from Swashbuckle.AspNetCore for parsing JSON to IOpenApiAny types

• TUnit for unit tests

• REST Client extension in Visual Studio Code for quick local tests via .http files

Design

Technically, the design is layered like the following flowchart.

flowchart TB

apis[BankApi.Service.Beta / BankApi.Service.Stable]
aspire[BankApi.Orchestration]
test[BankApi.Tests]

infra_gen[Infra.Generated]
specs_gen[Specs.Generated]
specs_downstream[Specs.Downstream]

subgraph core[BankApi.Core]
Defaults
DownstreamClients
Implementation
end

specs_downstream -- .kiota --> DownstreamClients
Defaults --> Implementation

DownstreamClients --> Defaults
DownstreamClients --> Implementation

Defaults --> apis
Implementation --> apis
Implementation --> test

apis --> aspire
apis --> specs_gen

aspire--> infra_gen

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Prerequisites

If not using the Dev Container, install:

• .NET 9 SDK

• All recommended Visual Studio Code extensions

Quick start

• Use a pwsh shell (for a click-a-long experience).

• (Optionally) regenerate the GitHub downstream API client by going to the Kiota workspace and clicking Re-generate under clients.

  

• Generate a new JWT-token for secured endpoints:

  dotnet user-jwts create --scope "bank_api" --role "banker" --project BankApi.Service.Stable

• Run dotnet build to output the OpenAPI definition

• Validate the OpenAPI definition by going to the openapi_v1.json definition and check for problems via the Spectral extension.

Run in Aspire minimal mode

This mode just runs the ASP.NET Core API.

1. Start the standalone Aspire Dashboard for developer visualization:

   docker run --rm -it `
     -p 18888:18888 `
     -p 4317:18889 `
     --name aspire-dashboard `
     mcr.microsoft.com/dotnet/aspire-dashboard:latest

   Copy the url shown in the resulting output when running the container, and replace 0.0.0.0 with localhost (e.g. http://localhost:18888/login?t=123456780abcdef123456780) and open that in a browser, or paste the key part seen after /login?t= when the login dialog is shown. The token will change each time the container is started.

2. Run the launch config API - Stable release channel.

Run in Aspire mode

This mode starts the API in the context of .NET Aspire.

1. Make sure the docker runtime is started.

2. Run the launch config Aspire Orchestration.

Considerations

General

1. OpenID Connect isn't fully supported in Scalar.

2. Running tests works in VSCode. However, debugging tests doesn't work with TUnit in VSCode yet.

3. To extend OpenTelemetry logging to Application Insights, expand the OpenTelemetry exporter.

4. The compliance NullRedactor doesn't seem to work, the redactor is already defined at Builder.Compliance.cs but not used because of the issue.

5. Dependabot is enabled for nuget packages but wildcard version notation isn't supported yet, which is used extensively in this project.

6. The OpenAPI document generator shipped with .NET 9 does not fully support API versioning, a simpler approach with PathBase is used for now, which is also more convenient for Azure API Management usage.

7. Extending Spectral rulesets from an NPM package can be problematic.

8. Generic exception handling is minimally implemented via ErrorHandling.cs.

9. API owners usually have customers outside of their own company - or outside of their own domain within a company - which inherently means adoption time will be slower for API contract changes, this is why there is a Stable and Beta version of the API in this project, inspired by the Microsoft Graph API Current/Beta versioning design. New or modified contract-breaking (beta) operations to API consumers may be served via the Beta version without distracting users on the Stable version.

   Do not confuse this versioning scheme as a replacement for DTAP; it is merely complementary to it. Many API changes will affect both the Stable and Beta endpoints (such as changes to the underlying shared database). That's why they both share a common layer in the form of BankApi.Core.

   Nonetheless, versioning is very opinionated and one should always see what the best business and technical fit is. This might change over time and from project to project.

Dev Container

1. Dev Containers with the docker-outside-of-docker feature instead of docker-in-docker do not work, for now we're using docker-in-docker.

2. The Aspire dashboard doesn't start the first time inside the Dev Container, open a new tab and paste the same URL, then it works.

3. Dev Containers in combination with Aspire Mode have port forwarding mismatch on endpoints, the ports shown for the Scalar pages in the Aspire Dashboard do not match the randomly assigned ports by Aspire. The Scalar pages are still accessible when using the ports assigned by Aspire (check the Ports View in VSCode).

Please see the Reddit r/dotnet post 1 and post 2 about this project for more considerations and information.

Troubleshooting

• If debugging isn't working properly, please clear the Extension Host Cache at %AppData%\Code\CachedData (on Windows) and restart VSCode.

• If getting the error unable to get local issuer certificate with Spectral, make sure to add the CA of the proxy to NODE_EXTRA_CA_CERTS and restart VSCode, for example:

[Environment]::SetEnvironmentVariable('NODE_EXTRA_CA_CERTS', 'C:\ZscalerRootCA.crt', 'User')

• Extending Rulesets with local filepath not refreshing when working on Spectral rulesets in VSCode. Force an update in the .spectral/main.yml when changing a file that is used as an extend.

License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.