In this article you are going to learn how to count unique IP addresses on page visits using Redis Sets and Go.

You are going to implement 2 simple REST endpoints to complete the exercise.

1. Running Redis with Docker #

Run Redis using Docker with this simple command:

docker run --rm --name redis 6379:6379 -d redis:latest

2. Initiating the Go Project #

Create a new Go project and install essential Redis and Chi packages. If you prefer a different HTTP router, feel free to use it.

# Create a new Go project
mkdir go-redis-sets

# Install Chi for routing
go get -u github.com/go-chi/chi/v5

# Install Redis package
go get github.com/redis/go-redis/v9

2.1 Connecting to Redis #

Connect your Go project to Redis.

package main

import (
	"context"
	"fmt"
	"github.com/redis/go-redis/v9"
)

func main() {
    ctx := context.Background()

    // Connect to Redis
    rdb := redis.NewClient(&redis.Options{
        Addr:     "localhost:6379",
        Password: "",
        DB:       0,
    })

    // Ping Redis to ensure the connection
    _, err := rdb.Ping(ctx).Result()
    if err != nil {
        panic(err)
    }
}
main.go

2.2 Setting up Chi Router #

Configure a Chi router for handling HTTP requests and run the server on port 8080.

package main

import (
	"context"
	"fmt"
	"net/http"
	"strings"

	"github.com/go-chi/chi/v5"
	"github.com/redis/go-redis/v9"
)

func main() {
    // ... (Existing redis code)

    // Create a new Chi router
    mux := chi.NewRouter()

    // Start the HTTP server
    http.ListenAndServe(":8080", mux)
}
main.go

3. Rest Endpoints #

Now let's implement REST 2 endpoints.

• One which will act as our main endpoint to collect IP addresses on.
• And another to list out all the IP addresses for a given endpoint.

3.1 GET article endpoint #

Use the Redis command SADD to add an item to a set.

Each time a request is received add the associated IP address to the associated "set" of the article.

package main

import (
	"context"
	"fmt"
	"net/http"
	"strings"

	"github.com/go-chi/chi/v5"
	"github.com/redis/go-redis/v9"
)

func main() {
    // ... (Existing code)

	mux.Get("/articles/{articleId}", func(w http.ResponseWriter, r *http.Request) {
		// Extract the 'articleId' parameter from the request URL
		articleId := chi.URLParam(r, "articleId")
	
		// Create a Redis key using the articleId for storage
		key := fmt.Sprintf("articles:%s", articleId)
	
		// Get client IP address
		ip := r.RemoteAddr
	
		// Add the IP address to a Redis Set associated with the article
		_, err := rdb.SAdd(r.Context(), key, ip).Result()
		if err != nil {
			fmt.Println(err)
	
			// Respond with an internal server error status and message
			w.WriteHeader(http.StatusInternalServerError)
			w.Write([]byte("internal server error"))
	
			return
		}
	
		// Respond with a success status and message
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("ok"))
	})
}
main.go

3.2 Get article metrics endpoint #

Write an endpoint to fetch the unique IP Addresses related to a given article.

Use the Redis command SMEMBERS to list out all the items inside a set.

package main

import (
	"context"
	"fmt"
	"net/http"
	"strings"

	"github.com/go-chi/chi/v5"
	"github.com/redis/go-redis/v9"
)

func main() {
    // ... (Existing code)

	mux.Get("/articles/{articleId}/metrics", func(w http.ResponseWriter, r *http.Request) {
		// Extract the 'articleId' parameter from the request URL
		articleId := chi.URLParam(r, "articleId")
	
		// Create a Redis key using the articleId for fetching metrics
		key := fmt.Sprintf("articles:%s", articleId)
	
		// Retrieve the members (IP addresses) from the Redis Set associated with the article
		members, err := rdb.SMembers(ctx, key).Result()
		if err != nil {
			fmt.Println(err)
	
			// Respond with an internal server error status and message
			w.WriteHeader(http.StatusInternalServerError)
			w.Write([]byte("internal server error"))
	
			return
		}
	
		// Respond with a success status and the joined members (IP addresses)
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(strings.Join(members, "\n")))
	})
}
main.go