refactor connectors for retry logic, add error view

connector/docker.go

@@ -17,27 +17,45 @@ type Docker struct {
 	client       *api.Client
 	containers   map[string]*container.Container
 	needsRefresh chan string // container IDs requiring refresh
+	closed       chan struct{}
 	lock         sync.RWMutex
 }
 
-func NewDocker() Connector {
+func NewDocker() (Connector, error) {
 	// init docker client
 	client, err := api.NewClientFromEnv()
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 	cm := &Docker{
 		client:       client,
 		containers:   make(map[string]*container.Container),
 		needsRefresh: make(chan string, 60),
+		closed:       make(chan struct{}),
 		lock:         sync.RWMutex{},
 	}
+
+	// query info as pre-flight healthcheck
+	info, err := client.Info()
+	if err != nil {
+		return nil, err
+	}
+
+	log.Debugf("docker-connector ID: %s", info.ID)
+	log.Debugf("docker-connector Driver: %s", info.Driver)
+	log.Debugf("docker-connector Images: %d", info.Images)
+	log.Debugf("docker-connector Name: %s", info.Name)
+	log.Debugf("docker-connector ServerVersion: %s", info.ServerVersion)
+
 	go cm.Loop()
 	cm.refreshAll()
 	go cm.watchEvents()
-	return cm
+	return cm, nil
 }
 
+// Docker implements Connector
+func (cm *Docker) Wait() struct{} { return <-cm.closed }
+
 // Docker events watcher
 func (cm *Docker) watchEvents() {
 	log.Info("docker event listener starting")
@@ -60,6 +78,8 @@ func (cm *Docker) watchEvents() {
 			cm.delByID(e.ID)
 		}
 	}
+	log.Info("docker event listener exited")
+	close(cm.closed)
 }
 
 func portsFormat(ports map[api.Port][]api.PortBinding) string {
@@ -114,7 +134,7 @@ func (cm *Docker) inspect(id string) *api.Container {
 	c, err := cm.client.InspectContainer(id)
 	if err != nil {
 		if _, ok := err.(*api.NoSuchContainer); !ok {
-			log.Errorf(err.Error())
+			log.Errorf("%s (%T)", err.Error(), err)
 		}
 	}
 	return c
@@ -125,7 +145,8 @@ func (cm *Docker) refreshAll() {
 	opts := api.ListContainersOptions{All: true}
 	allContainers, err := cm.client.ListContainers(opts)
 	if err != nil {
-		panic(err)
+		log.Errorf("%s (%T)", err.Error(), err)
+		return
 	}
 
 	for _, i := range allContainers {
@@ -137,9 +158,14 @@ func (cm *Docker) refreshAll() {
 }
 
 func (cm *Docker) Loop() {
-	for id := range cm.needsRefresh {
-		c := cm.MustGet(id)
-		cm.refresh(c)
+	for {
+		select {
+		case id := <-cm.needsRefresh:
+			c := cm.MustGet(id)
+			cm.refresh(c)
+		case <-cm.closed:
+			return
+		}
 	}
 }
 
@@ -161,7 +187,7 @@ func (cm *Docker) MustGet(id string) *container.Container {
 	return c
 }
 
-// Get a single container, by ID
+// Docker implements Connector
 func (cm *Docker) Get(id string) (*container.Container, bool) {
 	cm.lock.Lock()
 	c, ok := cm.containers[id]
@@ -177,7 +203,7 @@ func (cm *Docker) delByID(id string) {
 	log.Infof("removed dead container: %s", id)
 }
 
-// All returns array of all containers, sorted by field
+// Docker implements Connector
 func (cm *Docker) All() (containers container.Containers) {
 	cm.lock.Lock()
 	for _, c := range cm.containers {

connector/main.go

@@ -3,16 +3,88 @@ package connector
 import (
 	"fmt"
 	"sort"
+	"sync"
+	"time"
 
 	"github.com/bcicen/ctop/container"
 	"github.com/bcicen/ctop/logging"
 )
 
 var (
 	log     = logging.Init()
-	enabled = make(map[string]func() Connector)
+	enabled = make(map[string]ConnectorFn)
 )
 
+type ConnectorFn func() (Connector, error)
+
+type Connector interface {
+	// All returns a pre-sorted container.Containers of all discovered containers
+	All() container.Containers
+	// Get returns a single container.Container by ID
+	Get(string) (*container.Container, bool)
+	// Wait waits for the underlying connection to be lost before returning
+	Wait() struct{}
+}
+
+// ConnectorSuper provides initial connection and retry on failure for
+// an undlerying Connector type
+type ConnectorSuper struct {
+	conn   Connector
+	connFn ConnectorFn
+	err    error
+	lock   sync.RWMutex
+}
+
+func NewConnectorSuper(connFn ConnectorFn) *ConnectorSuper {
+	cs := &ConnectorSuper{
+		connFn: connFn,
+		err:    fmt.Errorf("connecting..."),
+	}
+	go cs.loop()
+	return cs
+}
+
+// Get returns the underlying Connector, or nil and an error
+// if the Connector is not yet initialized or is disconnected.
+func (cs *ConnectorSuper) Get() (Connector, error) {
+	cs.lock.RLock()
+	defer cs.lock.RUnlock()
+	if cs.err != nil {
+		return nil, cs.err
+	}
+	return cs.conn, nil
+}
+
+func (cs *ConnectorSuper) setError(err error) {
+	cs.lock.Lock()
+	defer cs.lock.Unlock()
+	cs.err = err
+}
+
+func (cs *ConnectorSuper) loop() {
+	const interval = 3
+	for {
+		log.Infof("initializing connector")
+
+		conn, err := cs.connFn()
+		if err != nil {
+			cs.setError(fmt.Errorf("%s\n\nattempting to reconnect...", err))
+			log.Errorf("failed to initialize connector: %s (%T)", err, err)
+			log.Errorf("retrying in %ds", interval)
+			time.Sleep(interval * time.Second)
+		} else {
+			cs.conn = conn
+			cs.setError(nil)
+			log.Infof("successfully initialized connector")
+
+			// wait until connection closed
+			cs.conn.Wait()
+			cs.setError(fmt.Errorf("attempting to reconnect..."))
+			log.Infof("connector closed")
+		}
+	}
+}
+
 // Enabled returns names for all enabled connectors on the current platform
 func Enabled() (a []string) {
 	for k, _ := range enabled {
@@ -22,14 +94,11 @@ func Enabled() (a []string) {
 	return a
 }
 
-func ByName(s string) (Connector, error) {
+// ByName returns a ConnectorSuper for a given name, or error if the connector
+// does not exists on the current platform
+func ByName(s string) (*ConnectorSuper, error) {
 	if cfn, ok := enabled[s]; ok {
-		return cfn(), nil
+		return NewConnectorSuper(cfn), nil
 	}
 	return nil, fmt.Errorf("invalid connector type \"%s\"", s)
 }
-
-type Connector interface {
-	All() container.Containers
-	Get(string) (*container.Container, bool)
-}

connector/mock.go

@@ -20,11 +20,11 @@ type Mock struct {
 	containers container.Containers
 }
 
-func NewMock() Connector {
+func NewMock() (Connector, error) {
 	cs := &Mock{}
 	go cs.Init()
 	go cs.Loop()
-	return cs
+	return cs, nil
 }
 
 // Create Mock containers
@@ -41,6 +41,15 @@ func (cs *Mock) Init() {
 
 }
 
+func (cs *Mock) Wait() struct{} {
+	ch := make(chan struct{})
+	go func() {
+		time.Sleep(30 * time.Second)
+		close(ch)
+	}()
+	return <-ch
+}
+
 func (cs *Mock) makeContainer(aggression int64) {
 	collector := collector.NewMock(aggression)
 	manager := manager.NewMock()

connector/runc.go

@@ -54,35 +54,44 @@ type Runc struct {
 	factory       libcontainer.Factory
 	containers    map[string]*container.Container
 	libContainers map[string]libcontainer.Container
+	closed        chan struct{}
 	needsRefresh  chan string // container IDs requiring refresh
 	lock          sync.RWMutex
 }
 
-func NewRunc() Connector {
+func NewRunc() (Connector, error) {
 	opts, err := NewRuncOpts()
-	runcFailOnErr(err)
+	if err != nil {
+		return nil, err
+	}
 
 	factory, err := getFactory(opts)
-	runcFailOnErr(err)
+	if err != nil {
+		return nil, err
+	}
 
 	cm := &Runc{
 		opts:          opts,
 		factory:       factory,
 		containers:    make(map[string]*container.Container),
 		libContainers: make(map[string]libcontainer.Container),
-		needsRefresh:  make(chan string, 60),
+		closed:        make(chan struct{}),
 		lock:          sync.RWMutex{},
 	}
 
 	go func() {
 		for {
-			cm.refreshAll()
-			time.Sleep(5 * time.Second)
+			select {
+			case <-cm.closed:
+				return
+			case <-time.After(5 * time.Second):
+				cm.refreshAll()
+			}
 		}
 	}()
 	go cm.Loop()
 
-	return cm
+	return cm, nil
 }
 
 func (cm *Runc) GetLibc(id string) libcontainer.Container {
@@ -141,7 +150,11 @@ func (cm *Runc) refresh(id string) {
 // Read runc root, creating any new containers
 func (cm *Runc) refreshAll() {
 	list, err := ioutil.ReadDir(cm.opts.root)
-	runcFailOnErr(err)
+	if err != nil {
+		log.Errorf("%s (%T)", err.Error(), err)
+		close(cm.closed)
+		return
+	}
 
 	for _, i := range list {
 		if i.IsDir() {
@@ -199,14 +212,6 @@ func (cm *Runc) MustGet(id string) *container.Container {
 	return c
 }
 
-// Get a single container, by ID
-func (cm *Runc) Get(id string) (*container.Container, bool) {
-	cm.lock.Lock()
-	defer cm.lock.Unlock()
-	c, ok := cm.containers[id]
-	return c, ok
-}
-
 // Remove containers by ID
 func (cm *Runc) delByID(id string) {
 	cm.lock.Lock()
@@ -216,7 +221,18 @@ func (cm *Runc) delByID(id string) {
 	log.Infof("removed dead container: %s", id)
 }
 
-// All returns array of all containers, sorted by field
+// Runc implements Connector
+func (cm *Runc) Wait() struct{} { return <-cm.closed }
+
+// Runc implements Connector
+func (cm *Runc) Get(id string) (*container.Container, bool) {
+	cm.lock.Lock()
+	defer cm.lock.Unlock()
+	c, ok := cm.containers[id]
+	return c, ok
+}
+
+// Runc implements Connector
 func (cm *Runc) All() (containers container.Containers) {
 	cm.lock.Lock()
 	for _, c := range cm.containers {
@@ -239,9 +255,3 @@ func getFactory(opts RuncOpts) (libcontainer.Factory, error) {
 	}
 	return libcontainer.New(opts.root, cgroupManager)
 }
-
-func runcFailOnErr(err error) {
-	if err != nil {
-		panic(fmt.Errorf("fatal runc error: %s", err))
-	}
-}