coredns/core/setup/errors.go

package setup

import (
	"io"
	"log"
	"os"

	"github.com/hashicorp/go-syslog"
	"github.com/miekg/coredns/middleware"
	"github.com/miekg/coredns/middleware/errors"
)

// Errors configures a new errors middleware instance.
func Errors(c *Controller) (middleware.Middleware, error) {
	handler, err := errorsParse(c)
	if err != nil {
		return nil, err
	}

	// Open the log file for writing when the server starts
	c.Startup = append(c.Startup, func() error {
		var err error
		var writer io.Writer

		switch handler.LogFile {
		case "visible":
			handler.Debug = true
		case "stdout":
			writer = os.Stdout
		case "stderr":
			writer = os.Stderr
		case "syslog":
			writer, err = gsyslog.NewLogger(gsyslog.LOG_ERR, "LOCAL0", "coredns")
			if err != nil {
				return err
			}
		default:
			if handler.LogFile == "" {
				writer = os.Stderr // default
				break
			}

			var file *os.File
			file, err = os.OpenFile(handler.LogFile, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
			if err != nil {
				return err
			}
			if handler.LogRoller != nil {
				file.Close()

				handler.LogRoller.Filename = handler.LogFile

				writer = handler.LogRoller.GetLogWriter()
			} else {
				writer = file
			}
		}

		handler.Log = log.New(writer, "", 0)
		return nil
	})

	return func(next middleware.Handler) middleware.Handler {
		handler.Next = next
		return handler
	}, nil
}

func errorsParse(c *Controller) (*errors.ErrorHandler, error) {
	// Very important that we make a pointer because the Startup
	// function that opens the log file must have access to the
	// same instance of the handler, not a copy.
	handler := &errors.ErrorHandler{}

	optionalBlock := func() (bool, error) {
		var hadBlock bool

		for c.NextBlock() {
			hadBlock = true

			what := c.Val()
			if !c.NextArg() {
				return hadBlock, c.ArgErr()
			}
			where := c.Val()

			if what == "log" {
				if where == "visible" {
					handler.Debug = true
				} else {
					handler.LogFile = where
					if c.NextArg() {
						if c.Val() == "{" {
							c.IncrNest()
							logRoller, err := parseRoller(c)
							if err != nil {
								return hadBlock, err
							}
							handler.LogRoller = logRoller
						}
					}
				}
			}
		}
		return hadBlock, nil
	}

	for c.Next() {
		// weird hack to avoid having the handler values overwritten.
		if c.Val() == "}" {
			continue
		}
		// Configuration may be in a block
		hadBlock, err := optionalBlock()
		if err != nil {
			return handler, err
		}

		// Otherwise, the only argument would be an error log file name or 'visible'
		if !hadBlock {
			if c.NextArg() {
				if c.Val() == "visible" {
					handler.Debug = true
				} else {
					handler.LogFile = c.Val()
				}
			}
		}
	}

	return handler, nil
}