probe package to trace & return errors

pkg/probe/probe.go

@@ -0,0 +1,157 @@
+/*
+ * Minimalist Object Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses)/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package probe implements a simple mechanism to trace and return errors in large programs.
+package probe
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+
+	"github.com/dustin/go-humanize"
+)
+
+// 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.Bytes(memstats.Alloc),
+		"mem.total":      humanize.Bytes(memstats.Sys),
+		"mem.heap.used":  humanize.Bytes(memstats.HeapAlloc),
+		"mem.heap.total": humanize.Bytes(memstats.HeapSys),
+	}
+}
+
+type tracePoint struct {
+	Line     int                 `json:"Line"`
+	Filename string              `json:"File"`
+	Function string              `json:"Func"`
+	Env      map[string][]string `json:"Env"`
+}
+
+// Error implements tracing error functionality.
+type Error struct {
+	lock        sync.Mutex
+	e           error
+	sysInfo     map[string]string
+	tracePoints []tracePoint
+}
+
+// New function instantiates an error probe for tracing. Original errors.error (golang's error
+// interface) is injected in only once during this New call. Rest of the time, you
+// trace the return path with Probe.Trace and finally handle reporting or quitting
+// at the top level.
+func New(e error) *Error {
+	return &Error{sync.Mutex{}, e, GetSysInfo(), []tracePoint{}}
+}
+
+// Trace records the point at which it is invoked. Stack traces are important for
+// debugging purposes.
+func (e *Error) Trace(fields ...string) *Error {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+
+	pc, file, line, _ := runtime.Caller(1)
+	function := runtime.FuncForPC(pc).Name()
+	_, function = filepath.Split(function)
+	file = "..." + strings.TrimPrefix(file, os.Getenv("GOPATH")) // trim gopathSource from file
+	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.tracePoints = append(e.tracePoints, tp)
+	return e
+}
+
+// Untrace erases last trace entry.
+func (e *Error) Untrace() {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+
+	l := len(e.tracePoints)
+	if l == 0 {
+		return
+	}
+	//	topTP := e.tracePoints[l-1]
+	e.tracePoints = e.tracePoints[:l-1]
+}
+
+// Error returns error string.
+func (e *Error) Error() string {
+	return e.String()
+}
+
+// String returns error message.
+func (e *Error) String() string {
+	trace := e.e.Error() + "\n"
+	for i, tp := range e.tracePoints {
+		if len(tp.Env) > 0 {
+			trace += fmt.Sprintf(" (%d) %s:%d %s(..) Tags: [%s]\n", i, tp.Filename, tp.Line, tp.Function, strings.Join(tp.Env["Tags"], ", "))
+		} else {
+			trace += fmt.Sprintf(" (%d) %s:%d %s(..)\n", i, tp.Filename, tp.Line, tp.Function)
+		}
+	}
+
+	trace += " Host:" + e.sysInfo["host.name"] + " | "
+	trace += "OS:" + e.sysInfo["host.os"] + " | "
+	trace += "Arch:" + e.sysInfo["host.arch"] + " | "
+	trace += "Lang:" + e.sysInfo["host.lang"] + " | "
+	trace += "Mem:" + e.sysInfo["mem.used"] + "/" + e.sysInfo["mem.total"] + " | "
+	trace += "Heap:" + e.sysInfo["mem.heap.used"] + "/" + e.sysInfo["mem.heap.total"]
+
+	return trace
+}
+
+// JSON returns JSON formated error trace.
+func (e *Error) JSON() string {
+	anonError := struct {
+		SysInfo     map[string]string
+		TracePoints []tracePoint
+	}{
+		e.sysInfo,
+		e.tracePoints,
+	}
+
+	//	jBytes, err := json.Marshal(anonError)
+	jBytes, err := json.MarshalIndent(anonError, "", "\t")
+	if err != nil {
+		return ""
+	}
+	return string(jBytes)
+}
+
+// ToError returns original emnedded error.
+func (e *Error) ToError() error {
+	return e.e
+}

pkg/probe/probe_test.go

@@ -0,0 +1,40 @@
+/*
+ * Minio Cloud Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package probe
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+func testDummy() *Error {
+	_, e := os.Stat("this-file-cannot-exit-234234232423423")
+	es := New(e)
+	es.Trace("this is hell", "asdf")
+	return es
+}
+
+func TestProbe(t *testing.T) {
+	es := testDummy()
+	if es == nil {
+		t.Fail()
+	}
+	es.Trace()
+	fmt.Println(es)
+	// fmt.Println(es.JSON())
+	// fmt.Println(es.ToError())
+}