gologging.md

About Golang Logging

A new function package will be created to manage logging in App Navigator Golang components, of which there are presently two:

1. Controller
2. Operator

Golang Logging Function

type LogLevel int
/* LogLevel values of LogLevel 
   LogLevel is what user requests 
*/
const ( 
        LogLevelNone  LogLevel = 0  
        LogLevelWarning LogLevel = 1
        LogLevelError LogLevel = 2
        LogLevelInfo LogLevel = 3
        LogLevelDebug LogLevel = 4
        LogLevelEntry LogLevel = 5
	     LogLevelAll LogLevel = 6
)

type LogType int 
/* LogType values of LogType 
   LogType is how code categorizes log message
*/
const (
        LogTypeEntry LogType = 0  
        LogTypeExit LogType = 1
        LogTypeInfo LogType = 2
        LogTypeWarning LogType = 3
        LogTypeError LogType = 4   
        LogTypeDebug LogType = 5
)

/*Logger interfaces*/
type Logger interface {
        SetLogLevel(logLevel LogLevel)       
        Log(goFileName string, funcName string, logType LogType, logData string, otherLogData string)
        IsEnabled(logType LogType) bool
}

/*NewLogger create new Logger*/ 
func NewLogger() Logger {}

type loggerImpl struct {
   /*global variable holds current log level*/
	LogLevel LogLevel
   /*global variable to hold current log type enablement flags*/ 
	LogTypeEnabled [6]bool 
}

/*Log write log entry to stdout. 
   Use getLogMessage func to format message 
*/ 
func (logger *loggerImpl) Log(goFileName string, funcName string, logType LogType, logData string) 

/*isEnabled guard function to test if desired logType is enabled */
func (logger *loggerImpl) IsEnabled(logType LogType) bool 

/*getLogMessage return log message as string in format: 
    [LogType] logData
*/ 
func (logger *loggerImpl) getLogMessage(logType LogType, logData string) string 

/*setLogTypes set log types */
func (logger *loggerImpl) setLogTypes(value bool) {}


/*SetLogLevel set global log level to specified value 
   set IsEnabled based on specified LogLevel as follows: 
   
   Log Level	   | Enabled Log Types
   -------------+----------------------------------------
   none	         |  set all to false 
   error	         |  error
   warning	      |  error, warning
   info	         |  error, warning, info
   debug	         |  error, warning, info, debug
   entry	         |  error, warning, info, entry, exit, debug
   all	         |  error, warning, info, entry, exit, debug
*/
func (logger *loggerImpl) SetLogLevel(logLevel LogLevel) 
     

Example;

if (logger.IsEnabled(LogTypeDebug)) {
   logger.Log(FileName(), FuncName(), LogTypeDebug, "this is a debug message")
}  
   

Regarding pre-existing use of klog/log

Controller uses k8s.io/klog:

klog.go provides functions to set Info, Warning, Error, Fatal messages, plus formatting variants such as Infof. It also provides V-style logging controlled by the -v and -vmodule=file=2 flags.

Info Warning Error Fatal

By default all log statements write to standard error, but klog provides some flags that modify default behavior

-logtostderr=true Logs are written to standard error instead of to files. -alsologtostderr=false Logs are written to standard error as well as to files. -stderrthreshold=ERROR Log events at or above this severity are logged to standard error as well as to files. -log_dir="" Log files will be written to this directory instead of the default temporary directory.

Other flags provide aids to debugging. -log_backtrace_at="" When set to a file and line number holding a logging statement, such as -log_backtrace_at=gopherflakes.go:234 a stack trace will be written to the Info log whenever execution hits that statement. (Unlike with -vmodule, the ".go" must be present.) -v=0 Enable V-leveled logging at the specified level. -vmodule="" The syntax of the argument is a comma-separated list of pattern=N, where pattern is a literal file name (minus the ".go" suffix) or "glob" pattern and N is a V level. For instance, -vmodule=gopher*=3 sets the V level to 3 in all Go files whose names begin "gopher".

For examples:

klog.Info("Prepare to repel boarders") klog.Fatalf("Initialization failed: %s", err) if klog.V(2) { klog.V(2).Infoln("Processed", nItems, "elements") }

Operator uses sigs.k8s.io/controller-runtime/pkg/runtime/log:

log.go contains (imports) following logging packages "github.com/go-logr/logr" "sigs.k8s.io/controller-runtime/pkg/log/zap"

log.go provides functions Error, Info, StacktraceLevel (record a stack trace for all messages at or above a given level), ...

Error Info

For examples:

log.Error(err, "unable to reconcile object", "object", object) log.Info("setting field foo on object", "value", targetValue, "object", object) log.StacktraceLevel()