feat(zfs-localpv): initial commit

provisioning and deprovisioning of
the volumes on the node where zfs pool
has already been setup. Pool name and the volume
parameters has to be given in storage class
which will be used to provision the volume.

Signed-off-by: Pawan <pawan@mayadata.io>

pkg/common/errors/errors.go

@@ -0,0 +1,99 @@
+/*
+Copyright 2019 The OpenEBS Authors
+
+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 errors
+
+import (
+	"fmt"
+)
+
+// New returns an error with the supplied message.
+// New also records the stack trace at the point it was called.
+func New(message string) error {
+	return &err{
+		prefix: stackTraceMessagePrefix,
+		msg:    message,
+		stack:  callers(),
+	}
+}
+
+// Errorf formats according to a format specifier and returns the string
+// as a value that satisfies error.
+// Errorf also records the stack trace at the point it was called.
+func Errorf(format string, args ...interface{}) error {
+	return &err{
+		prefix: stackTraceMessagePrefix,
+		msg:    fmt.Sprintf(format, args...),
+		stack:  callers(),
+	}
+}
+
+// Wrap annotates err with a new message.
+// If err is nil, Wrap returns nil.
+func Wrap(err error, message string) error {
+	if err == nil {
+		return nil
+	}
+	return &wrapper{wrapErrorMessagePrefix, message, err}
+}
+
+// Wrapf annotates err with the format specifier.
+// If err is nil, Wrapf returns nil.
+func Wrapf(err error, format string, args ...interface{}) error {
+	if err == nil {
+		return nil
+	}
+	return &wrapper{wrapErrorMessagePrefix, fmt.Sprintf(format, args...), err}
+}
+
+// WithStack annotates err with a stack trace at the
+// point WithStack was called. If err is nil, WithStack returns nil.
+func WithStack(err error) error {
+	if err == nil {
+		return nil
+	}
+	return &withStack{
+		stackTraceMessagePrefix,
+		err,
+		callers(),
+	}
+}
+
+// Cause returns the underlying cause of the error, if possible.
+// An error value has a cause if it implements the following
+// interface:
+//
+//     type causer interface {
+//            Cause() error
+//     }
+//
+// If the error does not implement Cause, the original error will
+// be returned. If the error is nil, nil will be returned without further
+// investigation.
+func Cause(err error) error {
+	type causer interface {
+		Cause() error
+	}
+
+	for err != nil {
+		cause, ok := err.(causer)
+		if !ok {
+			break
+		}
+		err = cause.Cause()
+	}
+	return err
+}

pkg/common/errors/types.go

@@ -0,0 +1,188 @@
+/*
+Copyright 2019 The OpenEBS Authors
+
+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 errors
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/pkg/errors"
+)
+
+const (
+	wrapErrorMessagePrefix  string = "  --  "
+	listErrorMessagePrefix  string = "  -  "
+	stackTraceMessagePrefix string = "      "
+)
+
+// stack represents a stack of program counters.
+type stack []uintptr
+
+// callers returns stack of caller function
+func callers() *stack {
+	const depth = 32
+	var pcs [depth]uintptr
+	n := runtime.Callers(3, pcs[:])
+	var st stack = pcs[0:n]
+	return &st
+}
+
+// err implements error interface that has a message and stack
+type err struct {
+	prefix string
+	msg    string
+	*stack
+}
+
+// Error is implementation of error interface
+func (e *err) Error() string { return e.msg }
+
+// Format is implementation of Formater interface
+func (e *err) Format(s fmt.State, verb rune) {
+	message := wrapErrorMessagePrefix + e.msg
+	switch verb {
+	case 'v':
+		if s.Flag('+') {
+			fmt.Fprint(s, message)
+			for i, pc := range *e.stack {
+				if i > 0 {
+					return
+				}
+				f := errors.Frame(pc)
+				fmt.Fprintf(s, "\n%s%+v", e.prefix, f)
+			}
+			return
+		}
+		fallthrough
+	case 's', 'q':
+		fmt.Fprint(s, message)
+	}
+}
+
+// wrapper implements error interface that has a message and error
+type wrapper struct {
+	prefix string
+	msg    string
+	error
+}
+
+// Error is implementation of error interface
+func (w *wrapper) Error() string { return w.msg }
+
+// Cause is implementation of causer interface
+func (w *wrapper) Cause() error { return w.error }
+
+// Format is implementation of Formater interface
+func (w *wrapper) Format(s fmt.State, verb rune) {
+	switch verb {
+	case 'v':
+		if s.Flag('+') {
+			fmt.Fprintf(s, "%+v\n", w.error)
+			fmt.Fprint(s, w.prefix+w.msg)
+			return
+		}
+		fallthrough
+	case 's', 'q':
+		fmt.Fprintf(s, "%s\n", w.error)
+		fmt.Fprint(s, w.prefix+w.msg)
+	}
+}
+
+// withStack implements error interface that has a stack and error
+type withStack struct {
+	prefix string
+	error
+	*stack
+}
+
+// Format is implementation of Formater interface
+func (ws *withStack) Format(s fmt.State, verb rune) {
+	message := wrapErrorMessagePrefix + fmt.Sprintf("%s", ws.error)
+	switch verb {
+	case 'v':
+		if s.Flag('+') {
+			fmt.Fprint(s, message)
+			for i, pc := range *ws.stack {
+				if i > 0 {
+					return
+				}
+				f := errors.Frame(pc)
+				fmt.Fprintf(s, "\n%s%+v", ws.prefix, f)
+			}
+			return
+		}
+		fallthrough
+	case 's', 'q':
+		fmt.Fprint(s, message)
+	}
+}
+
+// Cause is implementation of causer interface
+func (ws *withStack) Cause() error { return ws.error }
+
+// ErrorList is a wrapper over list of errors
+// It implements error interface
+type ErrorList struct {
+	Errors []error
+	msg    string
+}
+
+// Error is implementation of error interface
+func (el *ErrorList) Error() string {
+	message := ""
+	for _, err := range el.Errors {
+		message += err.Error() + ":"
+	}
+	el.msg = message
+	return message
+}
+
+// Format is implementation of Formater interface
+func (el *ErrorList) Format(s fmt.State, verb rune) {
+	message := ""
+	for _, err := range el.Errors {
+		message += "\n" + listErrorMessagePrefix + err.Error()
+	}
+	fmt.Fprint(s, message)
+
+}
+
+// WithStack annotates ErrorList with a new message and
+// stack trace of caller.
+func (el *ErrorList) WithStack(message string) error {
+	if el == nil {
+		return nil
+	}
+	return &withStack{
+		stackTraceMessagePrefix,
+		Wrap(el, message),
+		callers(),
+	}
+}
+
+// WithStackf annotates ErrorList with the format specifier
+// and stack trace of caller.
+func (el *ErrorList) WithStackf(format string, args ...interface{}) error {
+	if el == nil {
+		return nil
+	}
+	return &withStack{
+		stackTraceMessagePrefix,
+		Wrapf(el, format, args...),
+		callers(),
+	}
+}