Add loggly handler.

This handler sends log15 records to loggly.
No third party dependencies are required.

Author: GeertJohan

Diff for: ext/loggly/loggly.go

@@ -0,0 +1,177 @@
+package loggly
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+
+	"gopkg.in/inconshreveable/log15.v2"
+)
+
+const (
+	// TokenPlaceholder is used to replace the token in a URI or request with the actual client token.
+	TokenPlaceholder = `{token}`
+)
+
+var (
+	// EndpointBase can be modified to a custom URI.
+	// This should be done before a new LogglyHandler is created.
+	EndpointSingle = `https://logs-01.loggly.com/inputs/` + TokenPlaceholder
+
+	// EndpointBulkBase can be modified to a custom URI
+	// This should be done before a new LogglyHandler is created.
+	EndpointBulk = `https://logs-01.loggly.com/bulk/` + TokenPlaceholder
+)
+
+// LogglyHandler sends logs to Loggly.
+// LogglyHandler should be created by NewLogglyHandler.
+// Exported fields can be modified during setup, but should not be touched when the Handler is in use.
+// LogglyHandler implements log15.Handler
+type LogglyHandler struct {
+	// Client can be modified or replaced with a custom http.Client
+	Client *http.Client
+
+	// Defaults contains key/value items that are added to every log message.
+	// Extra values can be added during the log15 setup.
+	//
+	// NewLogglyHandler adds a single record: "hostname", with the return value from os.Hostname().
+	// When os.Hostname() returns with an error, the key "hostname" is not set and this map will be empty.
+	Defaults map[string]interface{}
+
+	// Tags are sent to loggly with the log.
+	Tags []string
+
+	// Endpoint can not be modified after the LogglyHandler was created.
+	endpointSingle string
+	endpointBulk   string
+}
+
+// NewLogglyHandler creates a new LogglyHandler instance
+// Exported field on the LogglyHandler can modified before it is being used.
+func NewLogglyHandler(token string) *LogglyHandler {
+	lh := &LogglyHandler{
+		endpointSingle: strings.Replace(EndpointSingle, TokenPlaceholder, token, -1),
+		endpointBulk:   strings.Replace(EndpointBulk, TokenPlaceholder, token, -1),
+
+		Client: &http.Client{},
+
+		Defaults: make(map[string]interface{}),
+	}
+
+	// if hostname is retrievable, set it as extra field
+	if hostname, err := os.Hostname(); err == nil {
+		lh.Defaults["hostname"] = hostname
+	}
+
+	return lh
+}
+
+// Log sends the given *log15.Record to loggly.
+// Standard fields are:
+//     - message, the record's message.
+//     - level, the record's level as string.
+//     - timestamp, the record's timestamp in UTC timezone truncated to microseconds.
+//     - context, (optional) the context fields from the record.
+// Extra fields are the configurable with the LogglyHandler.Defaults map
+// By default this contains:
+//     - hostname, the system hostname
+func (lh *LogglyHandler) Log(r *log15.Record) error {
+	// create message structure
+	msg := lh.createMessage(r)
+
+	// send message
+	err := lh.sendSingle(msg)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// createMessage takes a log15.Record and returns a loggly message structure
+func (lh *LogglyHandler) createMessage(r *log15.Record) map[string]interface{} {
+	// set standard values
+	msg := map[string]interface{}{
+		"message": r.Msg,
+		"level":   r.Lvl.String(),
+		// for loggly we need to truncate the timestamp to microsecond precision and convert it to UTC timezone
+		"timestamp": r.Time.Truncate(time.Microsecond).In(time.UTC),
+	}
+
+	// apply defaults
+	for key, value := range lh.Defaults {
+		msg[key] = value
+	}
+
+	// optionally add context
+	if len(r.Ctx) > 0 {
+		context := make(map[string]interface{}, len(r.Ctx)/2)
+		for i := 0; i < len(r.Ctx); i += 2 {
+			key := r.Ctx[i]
+			value := r.Ctx[i+1]
+			keyStr, ok := key.(string)
+			if !ok {
+				keyStr = fmt.Sprintf("%v", key)
+			}
+			context[keyStr] = value
+		}
+		msg["context"] = context
+	}
+
+	// got a nice message to deliver
+	return msg
+}
+
+// sendSingle sends a single loggly structure to their http endpoint
+func (lh *LogglyHandler) sendSingle(msg map[string]interface{}) error {
+	// encode the message to json
+	postBuffer := &bytes.Buffer{}
+	err := json.NewEncoder(postBuffer).Encode(msg)
+	if err != nil {
+		return err
+	}
+
+	// create request
+	req, err := http.NewRequest("POST", lh.endpointSingle, postBuffer)
+	req.Header.Add("User-Agent", "log15")
+	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Add("Content-Length", strconv.Itoa(postBuffer.Len()))
+
+	// apply tags
+	if len(lh.Tags) > 0 {
+		req.Header.Add("X-Loggly-Tag", strings.Join(lh.Tags, ","))
+	}
+
+	// do request
+	resp, err := lh.Client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	// check statuscode
+	if resp.StatusCode != 200 {
+		resp, _ := ioutil.ReadAll(resp.Body)
+		return fmt.Errorf("error: %s", string(resp))
+	}
+
+	// validate response
+	response := &logglyResponse{}
+	err = json.NewDecoder(resp.Body).Decode(&response)
+	if err != nil {
+		return err
+	}
+	if response.Response != "ok" {
+		return errors.New(`loggly response was not "ok"`)
+	}
+
+	// all done
+	return nil
+}

Diff for: ext/loggly/response.go

@@ -0,0 +1,9 @@
+package loggly
+
+//go:generate ffjson $GOFILE
+
+// logglyResponse defines the json returned by the loggly endpoint.
+// The value for Response should be "ok". Unmarshalling is optimized by ffjson.
+type logglyResponse struct {
+	Response string `json:"response"`
+}