feat(detected_fields): initial plumbing of new endpoint

* introduces an `experimental` api prefix
* establishes request/response for detected fields

cmd/loki/loki-local-experimental-config.yaml

@@ -0,0 +1,53 @@
+auth_enabled: false
+
+server:
+  http_listen_port: 3100
+  grpc_listen_port: 9096
+
+common:
+  instance_addr: 127.0.0.1
+  path_prefix: /tmp/loki
+  storage:
+    filesystem:
+      chunks_directory: /tmp/loki/chunks
+      rules_directory: /tmp/loki/rules
+  replication_factor: 1
+  ring:
+    kvstore:
+      store: inmemory
+
+query_range:
+  results_cache:
+    cache:
+      embedded_cache:
+        enabled: true
+        max_size_mb: 100
+
+schema_config:
+  configs:
+    - from: 2020-10-24
+      store: tsdb
+      object_store: filesystem
+      schema: v12
+      index:
+        prefix: index_
+        period: 24h
+
+frontend:
+  experimental_apis_enabled: true
+
+ruler:
+  alertmanager_url: http://localhost:9093
+
+# By default, Loki will send anonymous, but uniquely-identifiable usage and configuration
+# analytics to Grafana Labs. These statistics are sent to https://stats.grafana.org/
+#
+# Statistics help us better understand how Loki is used, and they show us performance
+# levels for most users. This helps us prioritize features and documentation.
+# For more information on what's sent, look at
+# https://github.com/grafana/loki/blob/main/pkg/analytics/stats.go
+# Refer to the buildReport method to see what goes into a report.
+#
+# If you would like to disable reporting, uncomment the following lines:
+#analytics:
+#  reporting_enabled: false

pkg/ingester/ingester.go

@@ -1359,3 +1359,15 @@ func adjustQueryStartTime(maxLookBackPeriod time.Duration, start, now time.Time)
 	}
 	return start
 }
+
+func (i *Ingester) GetDetectedFields(ctx context.Context, req *logproto.DetectedFieldsRequest) (*logproto.DetectedFieldsResponse, error) {
+	return &logproto.DetectedFieldsResponse{
+		Fields: []*logproto.DetectedField{
+			{
+				Label: "foo",
+				Type:  logproto.DetectedFieldString,
+				Cardinality:  1,
+			},
+		},
+	}, nil
+}

pkg/loghttp/labels.go

@@ -86,3 +86,17 @@ func ParseLabelQuery(r *http.Request) (*logproto.LabelRequest, error) {
 	req.Query = query(r)
 	return req, nil
 }
+
+func ParseDetectedFieldsQuery(r *http.Request) (*logproto.DetectedFieldsRequest, error) {
+	req := &logproto.DetectedFieldsRequest{}
+
+	start, end, err := bounds(r)
+	if err != nil {
+		return nil, err
+	}
+	req.Start = &start
+	req.End = &end
+
+	req.Query = query(r)
+	return req, nil
+}

pkg/logproto/extensions.go

@@ -133,3 +133,12 @@ func (m *IndexStatsResponse) LoggingKeyValues() []interface{} {
 		"entries", m.Entries,
 	}
 }
+
+const (
+	DetectedFieldString   DetectedFieldType = 0
+	DetectedFieldInt      DetectedFieldType = 1
+	DetectedFieldFloat    DetectedFieldType = 2
+	DetectedFieldBoolean  DetectedFieldType = 3
+	DetectedFieldDuration DetectedFieldType = 4
+	DetectedFieldBytes    DetectedFieldType = 5
+)