feat(config): allow no remote write configs

Signed-off-by: Julien Levesy <jlevesy@gmail.com>

config/config.go

@@ -112,10 +112,6 @@ func LoadFile(filename string, agentMode, expandExternalLabels bool, logger log.
 	}
 
 	if agentMode {
-		if len(cfg.RemoteWriteConfigs) == 0 {
-			return nil, errors.New("at least one remote_write target must be specified in agent mode")
-		}
-
 		if len(cfg.AlertingConfig.AlertmanagerConfigs) > 0 || len(cfg.AlertingConfig.AlertRelabelConfigs) > 0 {
 			return nil, errors.New("field alerting is not allowed in agent mode")
 		}

config/config_test.go

@@ -1745,6 +1745,33 @@ func TestExpandExternalLabels(t *testing.T) {
 	require.Equal(t, labels.FromStrings("bar", "foo", "baz", "fooTestValuebar", "foo", "TestValue", "qux", "foo${TEST}", "xyz", "foo$bar"), c.GlobalConfig.ExternalLabels)
 }
 
+func TestAgentMode(t *testing.T) {
+	_, err := LoadFile("testdata/agent_mode.with_alert_manager.yml", true, false, log.NewNopLogger())
+	require.ErrorContains(t, err, "field alerting is not allowed in agent mode")
+
+	_, err = LoadFile("testdata/agent_mode.with_alert_relabels.yml", true, false, log.NewNopLogger())
+	require.ErrorContains(t, err, "field alerting is not allowed in agent mode")
+
+	_, err = LoadFile("testdata/agent_mode.with_rule_files.yml", true, false, log.NewNopLogger())
+	require.ErrorContains(t, err, "field rule_files is not allowed in agent mode")
+
+	_, err = LoadFile("testdata/agent_mode.with_remote_reads.yml", true, false, log.NewNopLogger())
+	require.ErrorContains(t, err, "field remote_read is not allowed in agent mode")
+
+	c, err := LoadFile("testdata/agent_mode.without_remote_writes.yml", true, false, log.NewNopLogger())
+	require.NoError(t, err)
+	require.Len(t, c.RemoteWriteConfigs, 0)
+
+	c, err = LoadFile("testdata/agent_mode.good.yml", true, false, log.NewNopLogger())
+	require.NoError(t, err)
+	require.Len(t, c.RemoteWriteConfigs, 1)
+	require.Equal(
+		t,
+		"http://remote1/push",
+		c.RemoteWriteConfigs[0].URL.String(),
+	)
+}
+
 func TestEmptyGlobalBlock(t *testing.T) {
 	c, err := Load("global:\n", false, log.NewNopLogger())
 	require.NoError(t, err)

config/testdata/agent_mode.good.yml

@@ -0,0 +1,2 @@
+remote_write:
+  - url: http://remote1/push

config/testdata/agent_mode.with_alert_manager.yml

@@ -0,0 +1,6 @@
+alerting:
+  alertmanagers:
+    - scheme: https
+      static_configs:
+        - targets:
+            - "1.2.3.4:9093"

config/testdata/agent_mode.with_alert_relabels.yml

@@ -0,0 +1,5 @@
+alerting:
+  alert_relabel_configs:
+    - action: uppercase
+      source_labels: [instance]
+      target_label: instance

config/testdata/agent_mode.with_remote_reads.yml

@@ -0,0 +1,5 @@
+remote_read:
+  - url: http://remote1/read
+    read_recent: true
+    name: default
+    enable_http2: false

config/testdata/agent_mode.with_rule_files.yml

@@ -0,0 +1,3 @@
+rule_files:
+  - "first.rules"
+  - "my/*.rules"

config/testdata/agent_mode.without_remote_writes.yml

@@ -0,0 +1,2 @@
+global:
+  scrape_interval: 15s