Adds Docker caching to Travis. (#83)

.travis.yml

@@ -14,5 +14,18 @@
 
 sudo: required
 services: docker
+
+# Cache intermediate Docker layers. For a description of how this works, see:
+# https://giorgos.sealabs.net/docker-cache-on-travis-and-docker-112.html
+cache:
+  directories:
+    - /home/travis/docker/
+env:
+  global:
+    - DOCKER_CACHE_FILE=/home/travis/docker/cache.tar.gz
+before_install: scripts/load_docker_cache.sh
+
 install: true
-script: docker build ${TRAVIS_BUILD_DIR} -t cartographer
+script:
+  - docker build ${TRAVIS_BUILD_DIR} -t cartographer
+  - scripts/save_docker_cache.sh

Dockerfile

@@ -13,7 +13,9 @@
 # limitations under the License.
 
 FROM ubuntu:trusty
-COPY . cartographer
+COPY scripts/install_debs.sh cartographer/scripts/
 RUN cartographer/scripts/install_debs.sh && rm -rf /var/lib/apt/lists/*
+COPY scripts/install_ceres.sh cartographer/scripts/
 RUN cartographer/scripts/install_ceres.sh && rm -rf ceres-solver
+COPY . cartographer
 RUN cartographer/scripts/install_cartographer.sh && rm -rf cartographer

scripts/load_docker_cache.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+# Copyright 2016 The Cartographer Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Cache intermediate Docker layers. For a description of how this works, see:
+# https://giorgos.sealabs.net/docker-cache-on-travis-and-docker-112.html
+
+set -o errexit
+set -o verbose
+set -o pipefail
+
+if [ -f ${DOCKER_CACHE_FILE} ]; then
+  gunzip -c ${DOCKER_CACHE_FILE} | docker load;
+fi

scripts/save_docker_cache.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+# Copyright 2016 The Cartographer Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Cache intermediate Docker layers. For a description of how this works, see:
+# https://giorgos.sealabs.net/docker-cache-on-travis-and-docker-112.html
+
+set -o errexit
+set -o verbose
+set -o pipefail
+
+if [[ ${TRAVIS_BRANCH} == "master" ]] &&
+    [[ ${TRAVIS_PULL_REQUEST} == "false" ]]; then
+  mkdir -p $(dirname ${DOCKER_CACHE_FILE});
+  docker save $(docker history -q cartographer |
+      grep -v '<missing>') | gzip > ${DOCKER_CACHE_FILE};
+fi