From d94e7b4838af524bffe06330b35c72968bf54af6 Mon Sep 17 00:00:00 2001
From: Philipp Defner <philipp.defner@justwatch.com>
Date: Mon, 17 Feb 2025 15:34:39 +0100
Subject: [PATCH] Check if query names are unique across jobs

---
 exporter.go | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/exporter.go b/exporter.go
index 46a24307..b7ccd851 100644
--- a/exporter.go
+++ b/exporter.go
@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"cloud.google.com/go/cloudsqlconn"
 	"cloud.google.com/go/cloudsqlconn/mysql/mysql"
@@ -36,6 +37,22 @@ func NewExporter(logger log.Logger, configFile string) (*Exporter, error) {
 		return nil, err
 	}
 
+	// Validate config file before, this will otherwise break Prometheus metrics ("was collected before with the same name and label values")
+	uniqueQueries := make(map[string]struct{})
+	var duplicateQueries []string
+	for _, job := range cfg.Jobs {
+		for _, query := range job.Queries {
+			if _, ok := uniqueQueries[query.Name]; ok {
+				duplicateQueries = append(duplicateQueries, query.Name)
+				continue
+			}
+			uniqueQueries[query.Name] = struct{}{}
+		}
+	}
+	if len(duplicateQueries) > 0 {
+		return nil, fmt.Errorf("invalid config file, query name is not unique across jobs: %v", strings.Join(duplicateQueries, ", "))
+	}
+
 	var queryDurationHistogramBuckets []float64
 	if len(cfg.Configuration.HistogramBuckets) == 0 {
 		queryDurationHistogramBuckets = DefaultQueryDurationHistogramBuckets