ci: Don't use Travis caches for docker images

.travis.yml

@@ -183,7 +183,6 @@ matrix:
       if: branch = master AND type = push
       before_install: []
       install: []
-      cache: false
       sudo: false
       script:
         MESSAGE_FILE=$(mktemp -t msg.XXXXXX);
@@ -201,7 +200,12 @@ env:
     - secure: "cFh8thThqEJLC98XKI5pfqflUzOlxsYPRW20AWRaYOOgYHPTiGWypTXiPbGSKaeAXTZoOA+DpQtEmefc0U6lt9dHc7a/MIaK6isFurjlnKYiLOeTruzyu1z7PWCeZ/jKXsU2RK/88DBtlNwfMdaMIeuKj14IVfpepPPL71ETbuk="
 
 before_install:
-  - zcat $HOME/docker/rust-ci.tar.gz | docker load || true
+  # We'll use the AWS cli to download/upload cached docker layers, so install
+  # that here.
+  - if [ "$TRAVIS_OS_NAME" = linux ]; then
+      pip install --user awscli;
+      export PATH=$PATH:$HOME/.local/bin;
+    fi
   - mkdir -p $HOME/rustsrc
   # FIXME(#46924): these two commands are required to enable IPv6,
   # they shouldn't exist, please revert once more official solutions appeared.
@@ -286,23 +290,9 @@ after_failure:
   # it happened
   - dmesg | grep -i kill
 
-# Save tagged docker images we created and load them if they're available
-# Travis saves caches whether the build failed or not, nuke rustsrc if
-# the failure was while updating it (as it may be in a bad state)
-# https://github.com/travis-ci/travis-ci/issues/4472
-before_cache:
-  - docker history -q rust-ci |
-    grep -v missing |
-    xargs docker save |
-    gzip > $HOME/docker/rust-ci.tar.gz
-
 notifications:
   email: false
 
-cache:
-  directories:
-    - $HOME/docker
-
 before_deploy:
   - mkdir -p deploy/$TRAVIS_COMMIT
   - >

src/ci/docker/run.sh

@@ -27,6 +27,21 @@ travis_fold start build_docker
 travis_time_start
 
 if [ -f "$docker_dir/$image/Dockerfile" ]; then
+    if [ "$CI" != "" ]; then
+      cksum=$(find $docker_dir/$image $docker_dir/scripts -type f | \
+        sort | \
+        xargs cat | \
+        sha512sum | \
+        awk '{print $1}')
+      s3url="s3://$SCCACHE_BUCKET/docker/$cksum"
+      url="https://s3-us-west-1.amazonaws.com/$SCCACHE_BUCKET/docker/$cksum"
+      echo "Attempting to download $s3url"
+      set +e
+      loaded_images=$(curl $url | docker load | sed 's/.* sha/sha/')
+      set -e
+      echo "Downloaded containers:\n$loaded_images"
+    fi
+
     dockerfile="$docker_dir/$image/Dockerfile"
     if [ -x /usr/bin/cygpath ]; then
         context="`cygpath -w $docker_dir`"
@@ -40,6 +55,23 @@ if [ -f "$docker_dir/$image/Dockerfile" ]; then
       -t rust-ci \
       -f "$dockerfile" \
       "$context"
+
+    if [ "$s3url" != "" ]; then
+      digest=$(docker inspect rust-ci --format '{{.Id}}')
+      echo "Built container $digest"
+      if ! grep -q "$digest" <(echo "$loaded_images"); then
+        echo "Uploading finished image to $s3url"
+        set +e
+        docker history -q rust-ci | \
+          grep -v missing | \
+          xargs docker save | \
+          gzip | \
+          aws s3 cp - $s3url
+        set -e
+      else
+        echo "Looks like docker image is the same as before, not uploading"
+      fi
+    fi
 elif [ -f "$docker_dir/disabled/$image/Dockerfile" ]; then
     if [ -n "$TRAVIS_OS_NAME" ]; then
         echo Cannot run disabled images on travis!