luci-go: Basic support for event logging in Go.

common/eventlog/internal/logservice/logservice.go

+// Copyright 2016 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+// Package logservice provides a client which can be used to to collect and send batches of logs to the eventlog service.
+package logservice
+
+import (
+        "bytes"
+        "net/http"
+        "time"
+
+        "github.com/golang/protobuf/proto"
+
+        logpb "github.com/luci/luci-go/common/eventlog/proto"
+        "golang.org/x/net/context"
+)
+
+// Client sends event logs to the eventlog service.
+type Client struct {
+        HTTPClient *http.Client
+        serverAddr string
+        logSource  string
+}
+
+// NewClient constructs a new Client.
+// Users must call Close when the Client is no longer needed.
+func NewClient(serverAddr, logSourceName string) *Client {
+        return &Client{
+                serverAddr: serverAddr,
+                logSource:  logSourceName,
+        }
+}
+
+// TODO(mcgreevy): support bundling log requests.
+
+// LogSync synchronously logs events to the eventlog service.
+// The EventTime in each event must have been obtained from time.Now.
+func (c *Client) LogSync(ctx context.Context, events []*logpb.LogRequestLite_LogEventLite) error {
+        // TODO(mcgreevy): consider supporting custom clocks.
+        log := &logpb.LogRequestLite{
+                RequestTimeMs: proto.Int64(time.Now().UnixNano() / 1e6),
+                LogSourceName: &c.logSource,
+                LogEvent:      events,
+        }
+
+        buf, err := proto.Marshal(log)
+        if err != nil {
+                return err
+        }
+
+        req, err := http.NewRequest("POST", c.serverAddr, bytes.NewReader(buf))
+        if err != nil {
+                return err
+        }
+
+        req.Header.Set("Content-Type", "application/octet-stream")
+        req = req.WithContext(ctx)
+        resp, err := c.HTTPClient.Do(req)
+        if err != nil {
+                return err
+        }
+        resp.Body.Close()
+
+        return nil
+}
+
+// Close flushes any pending logs and releases any resources held by the client.
+// Close should be called when the client is no longer needed.
+func (c *Client) Close() error {
+        // We will need this later, but for now it's a no-op.
+        return nil
+}