Commit-Confirm Mechanic for PND

Description

This MR introduces a commit-confirm mechanic for changes to ONDs. A change created in a pending-state. A commit of this change by the operator pushed the change to the given OND. If the commit is not confirmed within 10 minutes (default. Use the GOSDN_CHANGE_TIMEOUT environment variable to change the timeout) is is rolled back automatically.

Related Issue

Closes #99 (closed)

Motivation and Context

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

nucleus/pnd/change.go

+package pnd
+
+import (
+	"github.com/google/uuid"
+	"github.com/openconfig/ygot/ygot"
+	log "github.com/sirupsen/logrus"
+	"sync"
+	"time"
+)
+
+func NewChange(device uuid.UUID, currentState ygot.GoStruct, change ygot.GoStruct, callback func(ygot.GoStruct, ygot.GoStruct) error) *Change {
+	return &Change{
+		cuid:          uuid.New(),
+		duid:          device,
+		timestamp:     time.Now(),
+		previousState: currentState,
+		intendedState: change,
+		committed:     false,
+		confirmed:     false,
+		callback:      callback,
+	}
+}
+
+// Change is an intended change to a OND. It is unique and immutable.
+// It has a cuid, a timestamp, and holds both the previous and the new
+// state. It keeps track if the state is committed and confirmed. A callback
+// exists to acess the proper transport for the changed OND
+type Change struct {
+	cuid          uuid.UUID
+	duid          uuid.UUID
+	timestamp     time.Time
+	previousState ygot.GoStruct
+	intendedState ygot.GoStruct
+	committed     bool
+	confirmed     bool
+	callback      func(ygot.GoStruct, ygot.GoStruct) error
+	lock          sync.RWMutex
+}
+
+func (c *Change) ID() uuid.UUID {
+	return c.cuid
+}
+
+func (c *Change) Commit() {
+	c.committed = true
+	if err := c.callback(c.intendedState, c.previousState); err != nil {
+		log.WithFields(log.Fields{
+			"change uuid": c.cuid,
+			"device uuid": c.duid,
+		}).Error(err)
+		log.WithFields(log.Fields{
+			"change uuid": c.cuid,
+			"device uuid": c.duid,
+		}).Debug("change commited")
+	}
+	go func() {
+		time.Sleep(time.Minute * 10)
+		c.lock.RLock()
+		defer c.lock.RUnlock()
+		if !c.confirmed {
+			c.Rollback()
+			log.WithFields(log.Fields{
+				"change uuid": c.cuid,
+				"device uuid": c.duid,
+			}).Error("change timed out")
+		}
+	}()
+}
+
+func (c *Change) Rollback() {
+	if err := c.callback(c.previousState, c.intendedState); err != nil {
+		log.WithFields(log.Fields{
+			"change uuid": c.cuid,
+			"device uuid": c.duid,
+		}).Error(err)
+	}
+}
+
+func (c *Change) Confirm() {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.confirmed = true
+	log.WithFields(log.Fields{
+		"change uuid": c.cuid,
+		"device uuid": c.duid,
+	}).Info("change confirmed")
+}