Mimir push reverse proxy in go

sqlite3 auth.db

CREATE TABLE users (
    username TEXT PRIMARY KEY,
    password TEXT NOT NULL
);

INSERT INTO users (username, password) VALUES ('admin', 'password123');

package main

import (
        "bytes" // "context" "database/sql" "encoding/base64" "fmt" "io"
        "log" "net/http" "net/url" "os" "strconv" "strings" "time"

        "github.com/golang/protobuf/proto" "github.com/golang/snappy"
        pb "github.com/prometheus/prometheus/prompb" _
        "github.com/mattn/go-sqlite3"
)

var db *sql.DB var mimirURL *url.URL var mimirUsername, mimirPassword
string var httpClient *http.Client

func parseRawMetric(raw string) (*pb.WriteRequest, error) {
        raw = strings.TrimSpace(raw)

        idxOpen := strings.Index(raw, "{") if idxOpen == -1 {
                return nil, fmt.Errorf("invalid format: missing '{'")
        } idxClose := strings.Index(raw, "}") if idxClose == -1 ||
        idxClose < idxOpen {
                return nil, fmt.Errorf("invalid format: missing '}'")
        }

        metricName := strings.TrimSpace(raw[:idxOpen])
        labelPart := raw[idxOpen+1 : idxClose] rest :=
        strings.TrimSpace(raw[idxClose+1:])

        parts := strings.Fields(rest) if len(parts) < 2 {
                return nil, fmt.Errorf("invalid format: missing value
                or timestamp")
        }

        value, err := strconv.ParseFloat(parts[0], 64) if err != nil {
                return nil, fmt.Errorf("invalid metric value: %v", err)
        }

        tsSec, err := strconv.ParseInt(parts[1], 10, 64) if err != nil {
                return nil, fmt.Errorf("invalid timestamp: %v", err)
        } timestamp := tsSec * 1000

        labels := []pb.Label{{Name: "__name__", Value: metricName}}
        labelPart = strings.TrimSpace(labelPart) if labelPart != "" {
                labelPairs := strings.Split(labelPart, ",") for _,
                pair := range labelPairs {
                        pair = strings.TrimSpace(pair) if pair == "" {
                                continue
                        } kv := strings.SplitN(pair, "=", 2) if len(kv)
                        != 2 {
                                return nil, fmt.Errorf("invalid label
                                format: %s", pair)
                        } key := strings.TrimSpace(kv[0]) val :=
                        strings.Trim(strings.TrimSpace(kv[1]), "\"")
                        labels = append(labels, pb.Label{Name: key,
                        Value: val})
                }
        }

        ts := pb.TimeSeries{
                Labels:  labels, Samples: []pb.Sample{{Value: value,
                Timestamp: timestamp}},
        }

        writeReq := &pb.WriteRequest{
                Timeseries: []pb.TimeSeries{ts},
        } return writeReq, nil
}

func main() {
        var err error db, err = sql.Open("sqlite3", "./auth.db") if err !=
        nil {
                log.Fatalf("Failed to open database: %v", err)
        } defer db.Close()

        mimirURLStr := os.Getenv("MIMIR_URL") if mimirURLStr == "" {
                mimirURLStr =
                "https://examplemimir.example.com/api/v1/push"
        } mimirURL, err = url.Parse(mimirURLStr) if err != nil {
                log.Fatalf("Invalid MIMIR_URL: %v", err)
        }

        mimirUsername = os.Getenv("MIMIR_USERNAME") if mimirUsername ==
        "" {
                mimirUsername = "your_username"
        } mimirPassword = os.Getenv("MIMIR_PASSWORD") if mimirPassword ==
        "" {
                mimirPassword = "your_password"
        }

        httpClient = &http.Client{
                Timeout: 10 * time.Second,
        }

        http.HandleFunc("/api/v1/push", func(w http.ResponseWriter,
        r *http.Request) {
                if !authenticate(r) {
                        http.Error(w, "Unauthorized",
                        http.StatusUnauthorized) return
                }

                data, err := io.ReadAll(r.Body) if err != nil {
                        http.Error(w, "Failed to read request body",
                        http.StatusInternalServerError) return
                } r.Body.Close()

                writeReq, err := parseRawMetric(string(data)) // writeReq
                is now used if err != nil {
                        http.Error(w, fmt.Sprintf("Failed to parse
                        metric: %v", err), http.StatusBadRequest)
                        log.Printf("Error parsing metric: %v, Raw data:
                        %s", err, string(data)) return
                }

                serialized, err := proto.Marshal(writeReq) if err != nil {
                        http.Error(w, "Failed to marshal protobuf
                        message", http.StatusInternalServerError)
                        log.Printf("Error marshaling protobuf: %v,
                        WriteRequest: %+v", err, writeReq) return
                }

                compressedData := snappy.Encode(nil, serialized)

                backendReq, err := http.NewRequestWithContext(r.Context(),
                "POST", mimirURL.String(),
                bytes.NewReader(compressedData)) if err != nil {
                        http.Error(w, "Failed to create backend request",
                        http.StatusInternalServerError) log.Printf("Error
                        creating backend request: %v", err) return
                } backendReq.Header.Set("Content-Type",
                "application/x-protobuf")
                backendReq.Header.Set("Content-Encoding", "snappy")
                backendReq.SetBasicAuth(mimirUsername, mimirPassword)

                resp, err := httpClient.Do(backendReq) if err != nil {
                        http.Error(w, fmt.Sprintf("Failed to push to
                        Mimir backend: %v", err), http.StatusBadGateway)
                        log.Printf("Error pushing to Mimir: %v, Mimir URL:
                        %s", err, mimirURL.String()) return
                } defer resp.Body.Close()

                if resp.StatusCode >= 400 {
                        body, _ := io.ReadAll(resp.Body) http.Error(w,
                        fmt.Sprintf("Mimir returned error: %s (Status
                        Code: %d)", string(body), resp.StatusCode),
                        http.StatusBadGateway) log.Printf("Mimir returned
                        error: %s (Status Code: %d), Mimir URL: %s",
                        string(body), resp.StatusCode, mimirURL.String())
                        return
                }

                w.WriteHeader(resp.StatusCode) io.Copy(w, resp.Body)
        })

        log.Println("HTTP server running on :8080")
        log.Fatal(http.ListenAndServe(":8080", nil))
}

func authenticate(r *http.Request) bool {
        authHeader := r.Header.Get("Authorization") if authHeader ==
        "" || !strings.HasPrefix(authHeader, "Basic ") {
                return false
        }

        decoded, err :=
        base64.StdEncoding.DecodeString(strings.TrimPrefix(authHeader,
        "Basic ")) if err != nil {
                return false
        }

        parts := strings.SplitN(string(decoded), ":", 2) if len(parts)
        != 2 {
                return false
        }

        username, password := parts[0], parts[1] return
        validateUser(username, password)
}

func validateUser(username, password string) bool {
        var storedPassword string err := db.QueryRow("SELECT password
        FROM users WHERE username = ?", username).Scan(&storedPassword)
        if err != nil {
                return false
        } return password == storedPassword
}

mkdir push-proxy
cd push-proxy
go mod init
go mod tidy
go build

set -a
MIMIR_URL=https://mimir.uvoo.io/api/v1/push
MIMIR_USERNAME=mybasicauthuser
MIMIR_PASSWORD=mybasicauthpass

simple test

curl -u admin:password123 http://localhost:8080/api/v1/push -d '{}'

simple test with data

curl -X POST -g \
    -u admin:password123 \
    --data "my_metric1{label1=\"value1\",label2=\"value2\"} 12.34 $(date +%s)" \
    http://localhost:8080/api/v1/push?job=my_job&instance=my_instance