goas

Tideland Go Application Support

Description

The Tideland Go Application Support (GOAS) is a collection of smaller helpful packages for multiple purposes. They are those little helpers we always need. See their descriptions below.

Installation

go get github.com/tideland/goas/v3/errors
go get github.com/tideland/goas/v2/identifier
go get github.com/tideland/goas/v2/logger
go get github.com/tideland/goas/v2/loop
go get github.com/tideland/goas/v2/monitoring
go get github.com/tideland/goas/v1/scroller
go get github.com/tideland/goas/v2/times

Usage

Errors

Typical errors in Go are often created using errors.New() or fmt.Errorf(). Those errors only contain a string as information. When trying to differentiate between errors or to carry helpful payload own types are needed.

The errors package allows to easily create formatted errors with errors.New() or errors.Annotate() like with the fmt.Errorf() function, but also with an error code. This easily can be tested with errors.IsError(err, code).

Identifier

The identifier packge provides different ways to produce identifiers like UUIDs. The UUID generation follows version 4 (based on random numbers), other identifier types are based on passed data or types. Here the individual parts are harmonized and concatenated by the passed seperators. It is the users responsibility to check if the identifier is unique in its context.

Logger

This package helps to log with different levels and on different backends like on an io.Writer or the Go logging. Own backends can be defined based on a simple interface. Setting the level controls what will be logged. Debug and critical logging also print filename, function name and line number.

Loop

A typical Go idiom for concurrent applications is running a loop in the background doing a select on one or more channels. Stopping those loops or getting aware of internal errors requires extra efforts. The loop package helps to manage this kind of goroutines.

The loop function, or method, looks like

func (f *Foo) backendLoop(l loop.Loop) error {
        select {
        case <-l.ShallStop():
                return nil
        case bar := <-f.barChan:
                ...
                if err != nil {
                        return err
                }
        case baz := <-f.bazChan:
                ...
                if err != nil {
                        return err
                }
        }
}

The loop is started with l := loop.Go(f.backendLoop). Now the loop can be stopped with l.Stop() which will return nil in case of no error or the error that has been returned by the loop during message processing. The loop also can be killed with l.Kill(err) or the status retrieved with status, err := l.Error(). The status is one of

• loop.Running,
• loop.Stopping, or
• loop.Stopped.

Another variant is loop.GoRecoverable(f.backendLoop, f.recoverFunc). Here a loop error or the value of a recovering after a panic are passed to the recover function. It then can decide if the loop shall be restarted or really terminated.

Monitoring

The monitoring package supports three kinds of system monitoring. They are helpful to understand what's happening inside a system during runtime. So execution times can be measured and analyzed, stay-set indicators integrated and dynamic control value retrieval provided.

etm := monitoring.BeginMeasuring("foo")
defer etm.EndMeasuring()

monitoring.SetVariable("bar", 4711)
monitoring.IncrVariable("bar")
monitoring.DecrVariable("bar")

monitoring.Register("baz", func() (string, error) { ... })

Scroller

A scroller allows a filtered streaming of lines from a Reader into a Writer. If the end of the data out of the reader is reached the scroller waits until new data is delivered.

Timex

The timex package supports the work with dates and times. Additionally it provides a simple crontab.

And now have fun. ;)

Documentation

• http://godoc.org/github.com/tideland/goas/v3/errors
• http://godoc.org/github.com/tideland/goas/v2/identifier
• http://godoc.org/github.com/tideland/goas/v2/logger
• http://godoc.org/github.com/tideland/goas/v2/loop
• http://godoc.org/github.com/tideland/goas/v2/monitoring
• http://godoc.org/github.com/tideland/goas/v1/scroller
• http://godoc.org/github.com/tideland/goas/v2/timex

Authors

• Frank Mueller - [email protected]

License

Tideland Go Application Support is distributed under the terms of the BSD 3-Clause license.