Implement image pull retry for tink-worker image

There could be races where linuxkit network or dns may not have been
fully set up and functional yet and image pull fails because of that.

Signed-off-by: Pooja Trivedi <tripooja@amazon.com>

Author: ptrivedi

hook-bootkit/go.sum

@@ -4,11 +4,14 @@ github.com/Azure/go-ansiterm v0.0.0-20210617225240-d185dfc1b5a1/go.mod h1:xomTg6
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/Microsoft/go-winio v0.4.16 h1:FtSW/jqD+l4ba5iPBj9CODVtgfYAD8w2wS923g/cFDk=
 github.com/Microsoft/go-winio v0.4.16/go.mod h1:XB6nPKklQyQ7GC9LdcBEcBl8PF76WugXOPRXwdLnMv0=
+github.com/cenkalti/backoff/v4 v4.1.3 h1:cFAlzYUlVYDysBEH2T5hyJZMh3+5+WCBvSnK6Q8UtC4=
+github.com/cenkalti/backoff/v4 v4.1.3/go.mod h1:scbssz8iZGpm3xbr14ovlUdkxfGXNInqkPWOWmG2CLw=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20200629203442-efcf912fb354/go.mod h1:WmhPx2Nbnhtbo57+VJT5O0JRkEi1Wbu0z5j0R8u5Hbk=
 github.com/containerd/containerd v1.4.3 h1:ijQT13JedHSHrQGWFcGEwzcNKrAGIiZ+jSD5QQG07SY=
 github.com/containerd/containerd v1.4.3/go.mod h1:bC6axHOhabU15QhwfG7w5PipXdVtMXFTttgp+kVtyUA=
+github.com/creack/pty v1.1.11 h1:07n33Z8lZxZ2qwegKbObQohDhXDQxiMMz1NOUGYlesw=
 github.com/creack/pty v1.1.11/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
@@ -153,6 +156,7 @@ google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2
 google.golang.org/protobuf v1.23.1-0.20200526195155-81db48ad09cc/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
 google.golang.org/protobuf v1.25.0 h1:Ejskq+SyPohKW+1uil0JJMtmHCgJPJ/qWTxr8qp+R4c=
 google.golang.org/protobuf v1.25.0/go.mod h1:9JNX74DMeImyA3h4bdi1ymwjUzf21/xIlbajtzgsN7c=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

hook-bootkit/main.go

@@ -13,6 +13,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/cenkalti/backoff/v4"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/api/types/mount"
@@ -47,6 +48,8 @@ type tinkConfig struct {
 	tinkServerTLS string
 }
 
+const maxRetryAttempts = 20
+
 func main() {
 	fmt.Println("Starting BootKit")
 
@@ -146,7 +149,21 @@ func main() {
 
 	fmt.Printf("Pulling image [%s]", imageName)
 
-	out, err := cli.ImagePull(ctx, imageName, pullOpts)
+	// TODO: Ideally if this function becomes a loop that runs forever and keeps retrying
+	// anything that failed, this retry would not be needed. For now, this addresses the specific
+	// race condition case of when the linuxkit network or dns is in the process of, but not quite
+	// fully set up yet.
+
+	var out io.ReadCloser
+	imagePullOperation := func() error {
+		out, err = cli.ImagePull(ctx, imageName, pullOpts)
+		if err != nil {
+			fmt.Printf("Image pull failure %s, %v\n", imageName, err)
+		}
+		return err
+	}
+	err = backoff.Retry(imagePullOperation, backoff.WithMaxRetries(backoff.NewExponentialBackOff(), maxRetryAttempts))
+
 	if err != nil {
 		panic(err)
 	}