[receiver/prometheus] Add fallback_scrape_protocol during config validation

.chloggen/prom-scrape-config-protocol.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: receiver/prometheus
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix Collector failing to start up if Prometheus receiver is present in config without 'fallback_scrape_protocol'.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [38018]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

exporter/datadogexporter/examples/collector-metrics.yaml

@@ -4,7 +4,6 @@ receivers:
       scrape_configs:
       - job_name: 'otelcol'
         scrape_interval: 10s
-        fallback_scrape_protocol: "PrometheusText1.0.0"
         static_configs:
         - targets: ['0.0.0.0:8888']
 

exporter/datadogexporter/examples/ootb-ec2.yaml

@@ -39,7 +39,6 @@ receivers:
       scrape_configs:
       - job_name: 'otelcol'
         scrape_interval: 10s
-        fallback_scrape_protocol: "PrometheusText1.0.0"
         static_configs:
         - targets: ['0.0.0.0:8888']
 

exporter/datadogexporter/integrationtest/integration_test_internal_metrics_config.yaml

@@ -11,7 +11,6 @@ receivers:
       scrape_configs:
         - job_name: 'otelcol'
           scrape_interval: 1s
-          fallback_scrape_protocol: "PrometheusText1.0.0"
           static_configs:
             - targets: [ '${env:PROM_SERVER}' ]
 

exporter/datadogexporter/integrationtest/integration_test_logs_config.yaml

@@ -11,7 +11,6 @@ receivers:
       scrape_configs:
         - job_name: 'otelcol'
           scrape_interval: 1s
-          fallback_scrape_protocol: "PrometheusText1.0.0"
           static_configs:
             - targets: [ '${env:PROM_SERVER}' ]
           metric_relabel_configs:

receiver/prometheusreceiver/config.go

@@ -103,6 +103,15 @@ func (cfg *PromConfig) Validate() error {
 	if err != nil {
 		return err
 	}
+	// Since Prometheus 3.0, the scrape manager started to fail scrapes that don't have proper
+	// Content-Type headers, but they provided an extra configuration option to fallback to the
+	// previous behavior. We need to make sure that this option is set for all scrape configs
+	// to avoid introducing a breaking change.
+	for _, sc := range scrapeConfigs {
+		if sc.ScrapeFallbackProtocol == "" {
+			sc.ScrapeFallbackProtocol = promconfig.PrometheusText0_0_4
+		}
+	}
 
 	for _, sc := range scrapeConfigs {
 		if err := validateHTTPClientConfig(&sc.HTTPClientConfig); err != nil {

receiver/prometheusreceiver/factory.go

@@ -63,7 +63,6 @@ func createMetricsReceiver(
 	nextConsumer consumer.Metrics,
 ) (receiver.Metrics, error) {
 	configWarnings(set.Logger, cfg.(*Config))
-	addDefaultFallbackScrapeProtocol(cfg.(*Config))
 	return newPrometheusReceiver(set, cfg.(*Config), nextConsumer), nil
 }
 
@@ -76,11 +75,3 @@ func configWarnings(logger *zap.Logger, cfg *Config) {
 		}
 	}
 }
-
-func addDefaultFallbackScrapeProtocol(cfg *Config) {
-	for _, sc := range cfg.PrometheusConfig.ScrapeConfigs {
-		if sc.ScrapeFallbackProtocol == "" {
-			sc.ScrapeFallbackProtocol = promconfig.PrometheusText1_0_0
-		}
-	}
-}

receiver/prometheusreceiver/factory_test.go

@@ -8,7 +8,6 @@ import (
 	"path/filepath"
 	"testing"
 
-	promconfig "github.com/prometheus/prometheus/config"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/component"
@@ -63,21 +62,3 @@ func TestMultipleCreate(t *testing.T) {
 	require.NoError(t, secondRcvr.Start(context.Background(), host))
 	require.NoError(t, secondRcvr.Shutdown(context.Background()))
 }
-
-func TestDefaultFallbackScrapeProtocol(t *testing.T) {
-	cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config_fallback_scrape_protocol.yaml"))
-	require.NoError(t, err)
-	factory := NewFactory()
-	cfg := factory.CreateDefaultConfig()
-
-	sub, err := cm.Sub(component.NewIDWithName(metadata.Type, "").String())
-	require.NoError(t, err)
-	assert.NoError(t, sub.Unmarshal(cfg))
-
-	_, err = factory.CreateMetrics(context.Background(), receivertest.NewNopSettings(), cfg, consumertest.NewNop())
-	require.NoError(t, err)
-
-	// During receiver creation, scrapeconfig without fallback scrape protocol set, should be set to 'PrometheusText1.0.0'.
-	assert.Equal(t, promconfig.PrometheusText1_0_0, cfg.(*Config).PrometheusConfig.ScrapeConfigs[0].ScrapeFallbackProtocol)
-	assert.Equal(t, promconfig.OpenMetricsText1_0_0, cfg.(*Config).PrometheusConfig.ScrapeConfigs[1].ScrapeFallbackProtocol)
-}

receiver/prometheusreceiver/internal/staleness_end_to_end_test.go

@@ -109,7 +109,6 @@ receivers:
       scrape_configs:
         - job_name: 'test'
           scrape_interval: 100ms
-          fallback_scrape_protocol: "PrometheusText1.0.0"
           static_configs:
             - targets: [%q]
 

receiver/prometheusreceiver/metrics_receiver_labels_test.go

@@ -7,7 +7,6 @@ import (
 	"testing"
 
 	"github.com/prometheus/common/model"
-	promconfig "github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/relabel"
 	"github.com/stretchr/testify/require"
@@ -258,7 +257,6 @@ func TestLabelNameLimitConfig(t *testing.T) {
 	testComponent(t, targets, nil, func(cfg *PromConfig) {
 		// set label limit in scrape_config
 		for _, scrapeCfg := range cfg.ScrapeConfigs {
-			scrapeCfg.ScrapeFallbackProtocol = promconfig.PrometheusText1_0_0
 			scrapeCfg.LabelNameLengthLimit = 20
 		}
 	})

receiver/prometheusreceiver/testdata/config_target_allocator.yaml

@@ -15,10 +15,8 @@ prometheus/withScrape:
     scrape_configs:
       - job_name: 'demo'
         scrape_interval: 5s
-        fallback_scrape_protocol: "PrometheusText1.0.0"
 prometheus/withOnlyScrape:
   config:
     scrape_configs:
       - job_name: 'demo'
         scrape_interval: 5s
-        fallback_scrape_protocol: "PrometheusText1.0.0"

receiver/prometheusreceiver/testdata/invalid-config-prometheus-file-sd-config-json.yaml

@@ -3,6 +3,5 @@ prometheus:
     scrape_configs:
       - job_name: 'demo'
         scrape_interval: 5s
-        fallback_scrape_protocol: "PrometheusText1.0.0"
         file_sd_configs:
         - files: ["./testdata/sd-config-with-null-target-group.json"]

receiver/prometheusreceiver/testdata/invalid-config-prometheus-file-sd-config-yaml.yaml

@@ -3,6 +3,5 @@ prometheus:
     scrape_configs:
       - job_name: 'demo'
         scrape_interval: 5s
-        fallback_scrape_protocol: "PrometheusText1.0.0"
         file_sd_configs:
         - files: ["./testdata/sd-config-with-null-target-group.yaml"]

receiver/prometheusreceiver/testdata/invalid-config-prometheus-nonexistent-scrape-config.yaml

@@ -17,4 +17,3 @@ prometheus/withOnlyScrape:
     scrape_configs:
       - job_name: 'demo'
         scrape_interval: 5s
-        fallback_scrape_protocol: "PrometheusText1.0.0"

receiver/prometheusreceiver/testdata/invalid-config-prometheus-unsupported-features.yaml

@@ -5,7 +5,6 @@ prometheus:
     scrape_configs:
       - job_name: 'demo'
         scrape_interval: 5s
-        fallback_scrape_protocol: "PrometheusText1.0.0"
     remote_write:
       - url: "https://example.org/write"
 

receiver/prometheusreceiver/testdata/nonexistent-prometheus-sd-file-config.yaml

@@ -3,6 +3,5 @@ prometheus:
     scrape_configs:
       - job_name: 'test'
         scrape_interval: 5s
-        fallback_scrape_protocol: "PrometheusText1.0.0"
         file_sd_configs:
         - files: ["./testdata/nonexistent-sd-file.json"]