log

README

log

log enables query logging to standard output.

Syntax

log

• With no arguments, a query log entry is written to stdout in the common log format for all requests

log FILE

• FILE is the log file to create (or append to). The only valid name for FILE is stdout.

log [NAME] FILE [FORMAT]

• NAME is the name to match in order to be logged
• FILE is the log file (again only stdout is allowed here).
• FORMAT is the log format to use (default is Common Log Format)

You can further specify the class of responses that get logged:

log [NAME] FILE [FORMAT] {
    class [success|denial|error|all]
}

Here success denial and error denotes the class of responses that should be logged. The classes have the following meaning:

• success: successful response
• denial: either NXDOMAIN or NODATA (name exists, type does not)
• error: SERVFAIL, NOTIMP, REFUSED, etc. Anything that indicates the remote server is not willing to resolve the request.
• all: the default - nothing is specified.

If no class is specified, it defaults to all.

Log File

The "log file" can only be stdout. CoreDNS expects another service to pick up this output and deal with it, i.e. journald when using systemd or Docker's logging capabilities.

Log Format

You can specify a custom log format with any placeholder values. Log supports both request and response placeholders.

The following place holders are supported:

• {type}: qtype of the request.
• {name}: qname of the request.
• {class}: qclass of the request.
• {proto}: protocol used (tcp or udp).
• {when}: time of the query.
• {remote}: client's IP address.
• {size}: request size in bytes.
• {port}: client's port.
• {duration}: response duration.
• {>bufsize}: the EDNS0 buffer size advertised.
• {>do}: is the EDNS0 DO (DNSSEC OK) bit set.
• {>id}: query ID
• {>opcode}: query OPCODE.
• {rcode}: response RCODE.
• {rsize}: response size.

The default Common Log Format is:

`{remote} - [{when}] "{type} {class} {name} {proto} {size} {>do} {>bufsize}" {rcode} {rsize} {duration}`

Examples

Log all requests to stdout

log stdout

Custom log format, for all zones (.)

log . stdout "{proto} Request: {name} {type} {>id}"

Only log denials for example.org (and below to a file)

log example.org stdout {
    class denial
}

Documentation

Overview

Package log implements basic but useful request (access) logging middleware.

Index

• Constants
• type Logger
  • func (l Logger) Name() string
  • func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)
• type Rule

Constants

const (
	// DefaultLogFilename is the default output name.
	DefaultLogFilename = "stdout"
	// CommonLogFormat is the common log format.
	CommonLogFormat = `{remote} ` + CommonLogEmptyValue + ` [{when}] "{type} {class} {name} {proto} {size} {>do} {>bufsize}" {rcode} {rsize} {duration}`
	// CommonLogEmptyValue is the common empty log value.
	CommonLogEmptyValue = "-"
	// CombinedLogFormat is the combined log format.
	CombinedLogFormat = CommonLogFormat + ` "{>opcode}"`
	// DefaultLogFormat is the default log format.
	DefaultLogFormat = CommonLogFormat
)

Types

type Logger

type Logger struct {
	Next      middleware.Handler
	Rules     []Rule
	ErrorFunc func(dns.ResponseWriter, *dns.Msg, int) // failover error handler
}

Logger is a basic request logging middleware.

func (Logger) Name

func (l Logger) Name() string

Name implements the Handler interface.

func (Logger) ServeDNS

func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)

ServeDNS implements the middleware.Handler interface.

type Rule

type Rule struct {
	NameScope  string
	Class      response.Class
	OutputFile string
	Format     string
	Log        *log.Logger
}

Rule configures the logging middleware.