Wait for IPFS to be ready during start

This commit introduces unlimited waiting on start until a request to `ipfs id`
succeeds.

Waiting has some consequences:

* State watching (recover/sync) and metrics publishing does not start until ipfs is ready
* swarm/connect is not triggered until ipfs is ready.

Once the first request to ipfs succeeds everything goes to what it was before.

This alleviates trying operations like sending our IDs in metrics when IPFS is
simply not there.

cluster.go

@@ -741,6 +741,20 @@ This might be due to one or several causes:
 		}
 	}
 
+	// Wait for ipfs
+	logger.Info("Waiting for IPFS to be ready...")
+	select {
+	case <-ctx.Done():
+		return
+	case <-c.ipfs.Ready(ctx):
+		ipfsid, err := c.ipfs.ID(ctx)
+		if err != nil {
+			logger.Error("IPFS signaled ready but ID() errored: ", err)
+		} else {
+			logger.Infof("IPFS is ready. Peer ID: %s", ipfsid.ID)
+		}
+	}
+
 	close(c.readyCh)
 	c.shutdownLock.Lock()
 	c.readyB = true

cluster_test.go

@@ -22,8 +22,8 @@ import (
 	"github.com/ipfs-cluster/ipfs-cluster/version"
 
 	gopath "github.com/ipfs/go-path"
-	peer "github.com/libp2p/go-libp2p/core/peer"
 	rpc "github.com/libp2p/go-libp2p-gorpc"
+	peer "github.com/libp2p/go-libp2p/core/peer"
 )
 
 type mockComponent struct {
@@ -53,6 +53,12 @@ type mockConnector struct {
 	blocks sync.Map
 }
 
+func (ipfs *mockConnector) Ready(ctx context.Context) <-chan struct{} {
+	ch := make(chan struct{})
+	close(ch)
+	return ch
+}
+
 func (ipfs *mockConnector) ID(ctx context.Context) (api.IPFSID, error) {
 	return api.IPFSID{
 		ID: test.PeerID1,

ipfscluster.go

@@ -1,9 +1,11 @@
-// Package ipfscluster implements a wrapper for the IPFS deamon which
-// allows to orchestrate pinning operations among several IPFS nodes.
+// Package ipfscluster is the heart of the IPFS Cluster implementation
+// gluing together all the subcomponents and performing the core functionality.
 //
-// IPFS Cluster peers form a separate libp2p swarm. A Cluster peer uses
-// multiple Cluster Components which perform different tasks like managing
-// the underlying IPFS daemons, or providing APIs for external control.
+// This package also provide the Cluster GO API through the Cluster object,
+// which allows to programatically build and control a cluster.
+//
+// For an example on how to initialize components and cluster object, see
+// cmd/ipfs-cluster-follow and cmd/ipfs-cluster-service.
 package ipfscluster
 
 import (
@@ -12,8 +14,8 @@ import (
 	"github.com/ipfs-cluster/ipfs-cluster/api"
 	"github.com/ipfs-cluster/ipfs-cluster/state"
 
-	peer "github.com/libp2p/go-libp2p/core/peer"
 	rpc "github.com/libp2p/go-libp2p-gorpc"
+	peer "github.com/libp2p/go-libp2p/core/peer"
 )
 
 // Component represents a piece of ipfscluster. Cluster components
@@ -73,6 +75,10 @@ type API interface {
 // an IPFS daemon. This is a base component.
 type IPFSConnector interface {
 	Component
+	//Ready provides a channel to notify when IPFS is ready. It allows the
+	//main cluster component to wait for IPFS to be in working state
+	//before starting full-fledge operations.
+	Ready(context.Context) <-chan struct{}
 	ID(context.Context) (api.IPFSID, error)
 	Pin(context.Context, api.Pin) error
 	Unpin(context.Context, api.Cid) error

ipfsconn/ipfshttp/ipfshttp.go

@@ -53,6 +53,7 @@ type Connector struct {
 
 	ctx    context.Context
 	cancel func()
+	ready  chan struct{}
 
 	config   *Config
 	nodeAddr string
@@ -168,8 +169,9 @@ func NewConnector(cfg *Config) (*Connector, error) {
 
 	ipfs := &Connector{
 		ctx:      ctx,
-		config:   cfg,
 		cancel:   cancel,
+		ready:    make(chan struct{}),
+		config:   cfg,
 		nodeAddr: nodeAddr,
 		rpcReady: make(chan struct{}, 1),
 		client:   c,
@@ -197,6 +199,27 @@ func initializeMetrics(ctx context.Context) {
 func (ipfs *Connector) run() {
 	<-ipfs.rpcReady
 
+	// wait for IPFS to be available
+	i := 0
+	for {
+		select {
+		case <-ipfs.ctx.Done():
+			return
+		default:
+		}
+		i++
+		_, err := ipfs.ID(ipfs.ctx)
+		if err == nil {
+			close(ipfs.ready)
+			break
+		}
+		if i%10 == 0 {
+			logger.Warningf("ipfs does not seem to be available after %d retries", i)
+		}
+
+		time.Sleep(time.Second)
+	}
+
 	// Do not shutdown while launching threads
 	// -- prevents race conditions with ipfs.wg.
 	ipfs.shutdownLock.Lock()
@@ -259,6 +282,12 @@ func (ipfs *Connector) Shutdown(ctx context.Context) error {
 	return nil
 }
 
+// Ready returns a channel which gets notified when a testing request to the
+// IPFS daemon first succeeds.
+func (ipfs *Connector) Ready(ctx context.Context) <-chan struct{} {
+	return ipfs.ready
+}
+
 // ID performs an ID request against the configured
 // IPFS daemon. It returns the fetched information.
 // If the request fails, or the parsing fails, it