Under Construction
grip
isn't any thing special, but it does a few pretty great
things:
- Provide a common logging interface with support for multiple logging backends including syslog, systemd's journal, slack, xmpp, a JSON logging system, and others.
- Provides some simple methods for handling errors, particularly when you want to accumulate and then return errors.
- Provides tools for collecting structured logging information.
You just get a grip, folks.
Download:
go get -u github.com/tychoish/grip
Import:
import "github.com/tychoish/grip"
Grip supports a number of different logging output backends:
- systemd's journal (linux-only)
- syslog (unix-only)
- writing messages to standard output. (default)
- writing messages to a file.
- sending messages to a slack's channel
- sending messages to a user via XMPP (jabber.)
The default logger interface has methods to switch the backend to the standard output (native; default), and file-based loggers. The SetSender() and CloneSender() methods allow to replace the sender implementation in your logger.
See the documentation of the Sender interface for more information on building new senders.
Provides a fully featured level-based logging system with multiple backends (e.g. send.Sender). By default logging messages are printed to standard output, but backends exists for many possible targets. The interface for logging is provided by the Journaler interface.
By default grip.std
defines a standard global instances
that you can use with a set of grip.<Level>
functions, or you can
create your own Journaler
instance and embed it in your own
structures and packages.
Defined helpers exist for the following levels/actions:
Debug
Info
Notice
Warning
Error
Critical
Alert
Emergency
EmergencyPanic
EmergencyFatal
Helpers ending with Panic
call panic()
after logging the message
message, and helpers ending with Fatal
call os.Exit(1)
after
logging the message. These are primarily for handling errors in your
main() function and should be used sparingly, if at all, elsewhere.
Journaler
instances have a notion of "default" log levels and
thresholds, which provide the basis for verbosity control and sane
default behavior. The default level defines the priority/level of any
message with an invalid priority specified. The threshold level,
defines the minimum priority or level that grip
sends to the
logging system. It's not possible to suppress the highest log level,
Emergency
messages will always log.
Journaler
objects have the following, additional methods (also
available as functions in the grip
package to manage the global
standard logger instance.):
SetName(<string>)
to reset the name of the logger.grip
attempts to set this to the name of your program for the standard logger.SetDefault(<level int>)
change the default log level. Levels are values between0
and7
, where lower numbers are more severe.grip
does not forbid configurations where default levels are below the configured threshold.SetThreshold(<level int>)
Change the lowest log level that thegrip
will transmit to the logging mechanism (eithersystemd
journald
or Go's standard logging.) Log messages with lower levels are not captured and ignored.
The Journaler.InvertFallback
flag (bool) switches a Journaler
instance to prefer the standard logging mechanism rather than
systemd
.
By default:
- the log level uses the "Notice" level (
5
) - the minimum threshold for logging is the "Info" level (
6
) (suppressing only debug.) - fallback logging writes to standard output.
If you want to do something other than just swallow errors, but don't
need to hard abort, the MultiCatcher
object makes this pattern
swell, a la:
func doStuff(dirname string) (error) { files, err := ioutil.ReadDir(dirname) if err != nil { // should abort here because we shouldn't continue. return err } catcher := grip.NewCatcher() for _, f := range files { err = doStuffToFile(f.Name()) catcher.Add(err) } return catcher.Resolve() }
Use grip.Catch(<err>)
to check and print error messages.
There are also helper functions on Journaler
objects that check
and log error messages using either the default (global) Journaler
instance, or as a method on specific Journaler
instances, at all
levels:
CatchDebug
CatchInfo
CatchNotice
CatchWarning
CatchError
CatchCritical
CatchAlert
CatchEmergency
CatchEmergencyPanic
CatchEmergencyFatal
grip
incldues support for conditional logging, so that you can
only log a message in certain situations, by adding a Boolean argument
to the logging call. Use this to implement "log sometimes" messages to
minimize verbosity without complicating the calling code around the
logging.
These methods have a <Level>When<>
format. For
example: AlertWhen
, AlertWhenln
, AlertWhenf
.
If the production of the log message is resource intensive or
complicated, you may wish to use a "composed logging," which delays
the generation of the log message from the logging call site to the
message propagation, to avoid generating the log message unless
neccessary. Rather than passing the log message as a string, pass the
logging function an instance of a type that implements the
MessageComposer
interface:
type MessageComposer interface { String() string Raw() interface{} Loggable() bool Priority() level.Priority SetPriority(level.Priority) error }
Composed logging may be useful for some debugging logging that depends
on additional database, API queries, or data serialization. Composers
are also the mechanism through which the Catch<>
methods are
implemented,
Grip uses composers internally, but you can pass composers directly to
any of the basic logging method (e.g. Info()
, Debug()
) for
composed logging.
Grip includes a number of message types, including those that collect system information, process information, stacktraces, or simple user-specified structured information.