prefetch test images

This gives more consistent test execution times, and also make image
fetch failures more apparent and decoupled from the tests.

We could *always* just run pull, but it's an expensive operation, so
we check for the presence of the image first. The downside is that we
could be running old images. That is not a problem on our CI
infrastructure though since it spins up fresh VMs per for every tun.

test/config.sh

@@ -31,6 +31,8 @@ SSH=${SSH:-ssh -l vagrant -i ./insecure_private_key -o UserKnownHostsFile=./.ssh
 
 SMALL_IMAGE="gliderlabs/alpine"
 DNS_IMAGE="aanand/docker-dnsutils"
+TEST_IMAGES="$SMALL_IMAGE $DNS_IMAGE"
+
 PING="ping -nq -W 1 -c 1"
 CHECK_ETHWE_UP="grep ^1$ /sys/class/net/ethwe/carrier"
 

test/setup.sh

@@ -6,7 +6,8 @@ set -e
 
 (cd ./tls && go get ./... && go run generate_certs.go $HOSTS)
 
-echo Copying weave images, scripts, and certificates to hosts
+echo "Copying weave images, scripts, and certificates to hosts, and"
+echo "  prefetch docker images"
 for HOST in $HOSTS; do
     docker_on $HOST load -i ../weave.tar
     docker_on $HOST load -i ../weavedns.tar
@@ -16,4 +17,7 @@ for HOST in $HOSTS; do
     cat ../weave | run_on $HOST sh -c "cat > ./weave"
     run_on $HOST chmod a+x $DOCKER_NS ./weave
     rsync -az -e "$SSH" ./tls/ $HOST:~/tls
+    for IMG in $TEST_IMAGES ; do
+        docker_on $HOST inspect --format=" " $IMG >/dev/null 2>&1 || docker_on $HOST pull $IMG
+    done
 done