/spring-cloud-config-server-steeltoe-demo

Demo of how to centralise and externalise configuration for multiple apps

Primary LanguageHTML

Existing Tool for Application Configuration Demo

Introduction

Situation:

  • need to provide different config for different environments.
  • some configs might be common across environments.

Rough set up in this demo:

  • Provider: Spring Cloud Config Server

    • takes care of reading/merging configs

  • Consumer: Steeltoe

    • C# library (OSS by Pivotal)

  • Proposed set up

    • decide and assign names to applications, eg. app1, app2.

      On the application side, we will specify this as a value in the respective app's appsettings.json (under Spring.Application.Name).

      In the config files side, we will write configs for an app (eg. app1) in a file of its same name (eg. app1.yml).

    • decide on environment names, eg. dev, qas, prod.

      On the application side, we will set ASPNETCORE_ENVIRONMENT to this value.

      In Spring Cloud Config, this corresponds to a "profile". We can place configs for different profiles in a single file (see app1.yml) - this works by default. We can also use a layout like {profile}/{application} where configs for a profile is placed in a subdirectory (see dev/qas/prod which contain app2.yml) - for filesystem as the "backend" for Spring Cloud Config, we'll need to add this pattern to the spring.cloud.config.server.native.searchLocations setting for Spring Cloud Config server to find them.

    • set up "backend" for config server - git repository, filesystem

    • tell app address of config server

    • usage in C# code:

      • inject IConfiguration from Microsoft.Extensions.Configuration (built-in), as usual - transparent to the app where the value is coming from

Advanced usage:

  • Backends can be combined - eg. filesystem + Git repository.
  • If Vault by Hashicorp is used for secrets, Spring Cloud Config server can use it as a backend too.
  • No need to specify Spring Cloud Config server url if you use a DiscoveryClient implementation, such as Spring Cloud Netflix and Eureka Service Discovery.
  • Spring Cloud Config server can monitor for changes in config (eg. pushes to Git repository, if Git repository is used as source of config) and send push notifications https://cloud.spring.io/spring-cloud-config/reference/html/#_push_notifications_and_spring_cloud_bus

Provider: Spring Cloud Config Server

A central place to manage external properties for applications across all environments.

It exposes a RESTful API:

/{application}/{profile}
/{application}-{profile}.yml
/{application}-{profile}.json
/{application}-{profile}.properties

application: app1, app2 profile: dev, test

For demonstration purposes, we have used the "filesystem" type as the source of config:

$ docker run \
  --publish 8888:8888 \
  --volume $(pwd)a-config-source:/config \
  steeltoeoss/config-server \
  --spring.profiles.active=native \
  --spring.cloud.config.server.native.searchLocations=file:///config,file:///config/{profile}

References:

Consumer: Steeltoe

What is Steeltoe?

References:

  1. Install Steeltoe:

    dotnet add package Steeltoe.Extensions.Configuration.ConfigServerCore

  2. Add Steeltoe to app, pick up HostingEnvironment (ie. ASPNETCORE_ENVIRONMENT):

diff --git a/Program.cs b/Program.cs
--- a/Program.cs
+++ b/Program.cs
@@ -6,6 +6,6 @@ using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
+using Steeltoe.Extensions.Configuration.ConfigServer;^M

namespace app1
{
diff --git a/Program.cs b/Program.cs
index 223e9ed..15603e2 100644
--- a/Program.cs
+++ b/Program.cs
@@ -14,4 +14,8 @@ namespace app1
        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
+                .ConfigureAppConfiguration((context, config) =>
+                {
+                    config.AddConfigServer(context.HostingEnvironment);
+                })
                .ConfigureWebHostDefaults(webBuilder =>
                {
  1. Tell Steeltoe the name of the app, and where to find Spring Cloud Config:
diff --git a/appsettings.json b/appsettings.json
--- a/appsettings.json
+++ b/appsettings.json
@@ -1,1 +1,11 @@
{
+  "Spring": {
+    "Application": {
+      "Name": "app1"
+    },
+    "Cloud": {
+      "Config": {
+        "Uri": "http://localhost:8888"
+      }
+    }
+  },
  1. Run app with the ASPNETCORE_ENVIRONMENT environment variable set to corresponding environment, eg. dev/qas/prod. (If running with dotnet run, remember to specify --no-launch-profiles for this to take effect). See .vscode/tasks.json for the demo apps launched.
# via dotnet run
$ ASPNETCORE_ENVIRONMENT=dev dotnet run --project app1/app1.csproj urls=https://localhost:5050 --no-launch-profile
$ ASPNETCORE_ENVIRONMENT=qas dotnet run --project app1/app1.csproj urls=https://localhost:5051 --no-launch-profile
$ ASPNETCORE_ENVIRONMENT=dev dotnet run --project app2/app2.csproj urls=https://localhost:6060 --no-launch-profile
$ ASPNETCORE_ENVIRONMENT=qas dotnet run --project app2/app2.csproj urls=https://localhost:6061 --no-launch-profile

# if dotnet build has already been run
$ ASPNETCORE_ENVIRONMENT=dev dotnet run app1/bin/Release/netcoreapp3.1/app1.dll urls=https://localhost:5050

Potential FAQs

Q: Is it ok to set ASPNETCORE_ENVIRONMENT to dev/qas/prod? I thought you can only set it to Development/Staging/Production.

A: Development/Staging/Production are the defaults, and there is no limitation on what values it is set to:

IHostEnvironment.EnvironmentName can be set to any value, but the following values are provided by the framework:

Development : The launchSettings.json file sets ASPNETCORE_ENVIRONMENT to Development on the local machine. Staging Production : The default if DOTNET_ENVIRONMENT and ASPNETCORE_ENVIRONMENT have not been set.

Source: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/environments

Q: I read about "labels" in Spring Cloud Config server. What is that?

A: For a Git repository as the source of configs, labels can correspond to a git label (commit id, branch name, or tag). They can be accessed via:

/{application}/{profile}[/{label}]
/{label}/{application}-{profile}.yml
/{label}/{application}-{profile}.json
/{label}/{application}-{profile}.properties