hooks: Add BugSnag hook

hooks/bugsnag/bugsnag.go

@@ -0,0 +1,53 @@
+package logrus_bugsnag
+
+import (
+	"github.com/Sirupsen/logrus"
+	"github.com/bugsnag/bugsnag-go"
+)
+
+// BugsnagHook sends exceptions to an exception-tracking service compatible
+// with the Bugsnag API. Before using this hook, you must call
+// bugsnag.Configure().
+//
+// Entries that trigger an Error, Fatal or Panic should now include an "error"
+// field to send to Bugsnag
+type BugsnagHook struct{}
+
+// Fire forwards an error to Bugsnag. Given a logrus.Entry, it extracts the
+// implicitly-required "error" field and sends it off.
+func (hook *BugsnagHook) Fire(entry *logrus.Entry) error {
+	if entry.Data["error"] == nil {
+		entry.Logger.WithFields(logrus.Fields{
+			"source": "bugsnag",
+		}).Warn("Exceptions sent to Bugsnag must have an 'error' key with the error")
+		return nil
+	}
+
+	err, ok := entry.Data["error"].(error)
+	if !ok {
+		entry.Logger.WithFields(logrus.Fields{
+			"source": "bugsnag",
+		}).Warn("Exceptions sent to Bugsnag must have an `error` key of type `error`")
+		return nil
+	}
+
+	bugsnagErr := bugsnag.Notify(err)
+	if bugsnagErr != nil {
+		entry.Logger.WithFields(logrus.Fields{
+			"source": "bugsnag",
+			"error":  bugsnagErr,
+		}).Warn("Failed to send error to Bugsnag")
+	}
+
+	return nil
+}
+
+// Levels enumerates the log levels on which the error should be forwarded to
+// bugsnag: everything at or above the "Error" level.
+func (hook *BugsnagHook) Levels() []logrus.Level {
+	return []logrus.Level{
+		logrus.ErrorLevel,
+		logrus.FatalLevel,
+		logrus.PanicLevel,
+	}
+}