Integration zerolog

[kuritka]

Related to #331
In order to integrate a zerolog, I had to create log package and take a few steps.

Log package

log package contains three components: factory, singleton and adapter.

loger factory, singleton

Instead of injecting *zerolog.Logger into each object (providers, assistant, etc). I created logger singleton.
This component is accessible from anywhere and contains one and only one instance of logger, which is accessible through reader function Logger()
Singleton must be initialised after resolving configuration and internally calls factory, which builds logger instance.
That's why logger factory is completely private now.

To inject logger into package do following:

import "github.com/AbsaOSS/k8gb/controllers/log"

// injection
var logger = log.Logger()

func MyFunc(){
 logger.Info().Msg("hello from logger")
}

Adapter

ControllerManager still calls logr internally. It can't use anything else. Unfortunately, the problem is that the logger inside ControllerManager completely ignores the settings of our logger, so plain text would appear between json records, etc.
It also ignores our formatting. The solution provides Adapter pattern
which basically allows us to encapsulate zerolog instance into logr interface. So on the outside it looks like logr but
internally it produces records by our zerolog instance. That's why logger within ControllerManager will print the same, expected way as we do in the rest of the application. Here is how we inject adapter:

// main.go
ctrl.SetLogger(log.NewAdapter(logger))
// controller manager has logger instance injected, and that's all. We don't need to do anything else.

logging messages

• I had to remove rlog and zapr from all components
• passing logger between components by arguments or structure fields was removed, now injection via singleton
• The way how we use zerolog:

logger.Info().Msg("hello from zerolog")
logger.Err(err).Msg("error from zerolog")  // prints "error from zerolog" and error
logger.Info().Msgf("hello from zerolog %s", stringvariable)
logger.Err(err).Msgf("error from zerolog %s", stringvariable)

• I made many replacements like this:

log.Info(fmt.Sprintf("%s annotation is missing, skipping Gslb creation...", primaryGeoTagAnnotation))
# I replaced with
logger.Info().Msgf("%s annotation is missing, skipping Gslb creation...", primaryGeoTagAnnotation)

• We had places where we printed Info messages within errors. I replaced them by Warnings.

IPs, err := utils.Dig(r.edgeDNSServer, lbHostname)
	if err != nil {
		logger.Warn().Msgf("Can't dig k8gb-coredns-lb service loadbalancer fqdn %s (%s)", lbHostname, err)
		return nil, err
	}

Output

Controller manager producing log with zapr

Controller manager producing logs with Adapter in json

Controller manager producing logs with Adapter in simple

TODO

• identify places for debug messages
• We don't need to print everything on info level, some info messages would go to debug
• We don't want to generate errors like this:

github.com/go-logr/zapr.(*zapLogger).Error
        /Users/ab011th/go/pkg/mod/github.com/go-logr/zapr@v0.4.0/zapr.go:132
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler
        /Users/ab011th/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.6.4/pkg/internal/controller/controller.go:246
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem
        /Users/ab011th/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.6.4/pkg/internal/controller/controller.go:218
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).worker
        /Users/ab011th/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.6.4/pkg/internal/controller/controller.go:197
k8s.io/apimachinery/pkg/util/wait.BackoffUntil.func1
        /Users/ab011th/go/pkg/mod/k8s.io/apimachinery@v0.20.4/pkg/util/wait/wait.go:155
k8s.io/apimachinery/pkg/util/wait.BackoffUntil
        /Users/ab011th/go/pkg/mod/k8s.io/apimachinery@v0.20.4/pkg/util/wait/wait.go:156
k8s.io/apimachinery/pkg/util/wait.JitterUntil
        /Users/ab011th/go/pkg/mod/k8s.io/apimachinery@v0.20.4/pkg/util/wait/wait.go:133
k8s.io/apimachinery/pkg/util/wait.Until
        /Users/ab011th/go/pkg/mod/k8s.io/apimachinery@v0.20.4/pkg/util/wait/wait.go:90

Instead, we want to have simplified view in JSON. I'll need to rewrite all error producing into
github.com/pkg/errors.

[ytsarev]

Some minor changes/questions.

Otherwise, it is a really great change 👍

@somaritane @k0da PR is huge, another pair of reviewing eyes will not hurt here :)

[somaritane]

lgtm!

[ytsarev]

Great stuff 👍