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probe.go
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probe.go
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// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
// Package probe implements a simple mechanism to trace and return errors in large programs.
package probe
import (
"fmt"
"os"
"path/filepath"
"runtime"
"strconv"
"strings"
"sync"
"github.com/dustin/go-humanize"
)
var (
// Root path to the project's source.
rootPath string
// App specific info to be included reporting.
appInfo map[string]string
)
// Init initializes probe. It is typically called once from the main()
// function or at least from any source file placed at the top level
// source directory.
func Init() {
// Root path is automatically determined from the calling function's source file location.
// Catch the calling function's source file path.
_, file, _, _ := runtime.Caller(1)
// Save the directory alone.
rootPath = filepath.Dir(file)
appInfo = make(map[string]string)
}
// SetAppInfo sets app speific key:value to report additionally during call trace dump.
// Eg. SetAppInfo("ReleaseTag", "RELEASE_42_0")
//
// SetAppInfo("Version", "42.0")
// SetAppInfo("Commit", "00611fb")
func SetAppInfo(key, value string) {
appInfo[key] = value
}
// GetSysInfo returns useful system statistics.
func GetSysInfo() map[string]string {
host, err := os.Hostname()
if err != nil {
host = ""
}
memstats := &runtime.MemStats{}
runtime.ReadMemStats(memstats)
return map[string]string{
"host.name": host,
"host.os": runtime.GOOS,
"host.arch": runtime.GOARCH,
"host.lang": runtime.Version(),
"host.cpus": strconv.Itoa(runtime.NumCPU()),
"mem.used": humanize.IBytes(memstats.Alloc),
"mem.total": humanize.IBytes(memstats.Sys),
"mem.heap.used": humanize.IBytes(memstats.HeapAlloc),
"mem.heap.total": humanize.IBytes(memstats.HeapSys),
}
}
// TracePoint container for individual trace entries in overall call trace
type TracePoint struct {
Line int `json:"line,omitempty"`
Filename string `json:"file,omitempty"`
Function string `json:"func,omitempty"`
Env map[string][]string `json:"env,omitempty"`
}
// Error implements tracing error functionality.
type Error struct {
lock sync.RWMutex
Cause error `json:"cause,omitempty"`
CallTrace []TracePoint `json:"trace,omitempty"`
SysInfo map[string]string `json:"sysinfo,omitempty"`
}
// NewError function instantiates an error probe for tracing.
// Default “error“ (golang's error interface) is injected in
// only once. Rest of the time, you trace the return path with
// “probe.Trace“ and finally handling them at top level
//
// Following dummy code talks about how one can pass up the
// errors and put them in CallTrace.
//
// func sendError() *probe.Error {
// return probe.NewError(errors.New("Help Needed"))
// }
// func recvError() *probe.Error {
// return sendError().Trace()
// }
// if err := recvError(); err != nil {
// log.Fatalln(err.Trace())
// }
func NewError(e error) *Error {
if e == nil {
return nil
}
Err := Error{lock: sync.RWMutex{}, Cause: e, CallTrace: []TracePoint{}, SysInfo: GetSysInfo()}
return Err.trace() // Skip NewError and only instead register the NewError's caller.
}
// Trace records the point at which it is invoked.
// Stack traces are important for debugging purposes.
func (e *Error) Trace(fields ...string) *Error {
if e == nil {
return nil
}
e.lock.Lock()
defer e.lock.Unlock()
return e.trace(fields...)
}
// trace records caller's caller. It is intended for probe's own
// internal use. Take a look at probe.NewError for example.
func (e *Error) trace(fields ...string) *Error {
if e == nil {
return nil
}
pc, file, line, _ := runtime.Caller(2)
function := runtime.FuncForPC(pc).Name()
_, function = filepath.Split(function)
file = strings.TrimPrefix(file, rootPath+string(os.PathSeparator)) // trims project's root path.
var tp TracePoint
if len(fields) > 0 {
tp = TracePoint{Line: line, Filename: file, Function: function, Env: map[string][]string{"Tags": fields}}
} else {
tp = TracePoint{Line: line, Filename: file, Function: function}
}
e.CallTrace = append(e.CallTrace, tp)
return e
}
// Untrace erases last known trace entry.
func (e *Error) Untrace() *Error {
if e == nil {
return nil
}
e.lock.Lock()
defer e.lock.Unlock()
l := len(e.CallTrace)
if l == 0 {
return nil
}
e.CallTrace = e.CallTrace[:l-1]
return e
}
// ToGoError returns original error message.
func (e *Error) ToGoError() error {
if e == nil || e.Cause == nil {
return nil
}
return e.Cause
}
// String returns error message.
func (e *Error) String() string {
if e == nil || e.Cause == nil {
return "<nil>"
}
e.lock.RLock()
defer e.lock.RUnlock()
if e.Cause != nil {
str := e.Cause.Error()
callLen := len(e.CallTrace)
for i := callLen - 1; i >= 0; i-- {
if len(e.CallTrace[i].Env) > 0 {
str += fmt.Sprintf("\n (%d) %s:%d %s(..) Tags: [%s]",
i, e.CallTrace[i].Filename, e.CallTrace[i].Line, e.CallTrace[i].Function, strings.Join(e.CallTrace[i].Env["Tags"], ", "))
} else {
str += fmt.Sprintf("\n (%d) %s:%d %s(..)",
i, e.CallTrace[i].Filename, e.CallTrace[i].Line, e.CallTrace[i].Function)
}
}
str += "\n "
for key, value := range appInfo {
str += key + ":" + value + " | "
}
str += "Host:" + e.SysInfo["host.name"] + " | "
str += "OS:" + e.SysInfo["host.os"] + " | "
str += "Arch:" + e.SysInfo["host.arch"] + " | "
str += "Lang:" + e.SysInfo["host.lang"] + " | "
str += "Mem:" + e.SysInfo["mem.used"] + "/" + e.SysInfo["mem.total"] + " | "
str += "Heap:" + e.SysInfo["mem.heap.used"] + "/" + e.SysInfo["mem.heap.total"]
return str
}
return "<nil>"
}