receiver/prometheus: start implementation. (#267)

Author: songy23

receiver/prometheus/doc.go

@@ -0,0 +1,17 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package prometheus has the logic for scraping Prometheus metrics from
+// already instrumented applications and then passing them onto a metricsink instance.
+package prometheus

receiver/prometheus/metrics_receiver.go

@@ -0,0 +1,50 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prometheus
+
+import (
+	"errors"
+	"time"
+
+	"github.com/census-instrumentation/opencensus-service/receiver"
+)
+
+// Receiver is the type used to handle metrics from OpenCensus exporters.
+type Receiver struct {
+	metricSink         receiver.MetricsReceiverSink
+	metricBufferPeriod time.Duration
+	metricBufferCount  int
+}
+
+// New creates a new prometheus.Receiver reference.
+func New(ms receiver.MetricsReceiverSink, opts ...Option) (*Receiver, error) {
+	if ms == nil {
+		return nil, errors.New("needs a non-nil receiver.MetricsReceiverSink")
+	}
+	pr := &Receiver{metricSink: ms}
+	for _, opt := range opts {
+		opt.WithReceiver(pr)
+	}
+	return pr, nil
+}
+
+const receiverName = "prometheus"
+
+// Export is the gRPC method that exports streamed metrics from
+// OpenCensus-metricproto compatible libraries/applications to MetricSink.
+func (pr *Receiver) Export() error {
+	// TODO: scrape metrics from Prometheus endpoint and convert to OC metrics.
+	return nil
+}

receiver/prometheus/options.go

@@ -0,0 +1,56 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prometheus
+
+import "time"
+
+// Option interface defines for configuration settings to be applied to receivers.
+//
+// WithReceiver applies the configuration to the given receiver.
+type Option interface {
+	WithReceiver(*Receiver)
+}
+
+type metricBufferPeriod struct {
+	period time.Duration
+}
+
+var _ Option = (*metricBufferPeriod)(nil)
+
+func (mfd *metricBufferPeriod) WithReceiver(ocr *Receiver) {
+	ocr.metricBufferPeriod = mfd.period
+}
+
+// WithMetricBufferPeriod is an option that allows one to configure
+// the period that spans are buffered for before the Receiver
+// sends them to its MetricsReceiver.
+func WithMetricBufferPeriod(period time.Duration) Option {
+	return &metricBufferPeriod{period: period}
+}
+
+type metricBufferCount int
+
+var _ Option = (*metricBufferCount)(nil)
+
+func (mpc metricBufferCount) WithReceiver(oci *Receiver) {
+	oci.metricBufferCount = int(mpc)
+}
+
+// WithMetricBufferCount is an option that allows one to configure
+// the number of metrics that are buffered before the Receiver
+// send them to its MetricsReceiverSink.
+func WithMetricBufferCount(count int) Option {
+	return metricBufferCount(count)
+}