Bazel: Make android tools scripts Python3-compatible for building android apps

[angerson]

Description of the problem / feature request / question:

Google's TFLite team has discovered that the TF Lite Android demo application cannot build via Bazel with Python 3, because the android tools Bazel uses aren't Python-3 compatible. The first breaking point looks like third_party/gflags, but past that there seem to be additional version incompatibilities.

If possible, provide a minimal example to reproduce the problem:

Here's a very fast example:

$ git clone http://github.com/bazelbuild/bazel /tmp/bazel
$ cd /tmp/bazel
$ python3
>>> import tools.android.aar_embedded_jars_extractor

I'm not actually sure how to do the same as the above in python 2, but that sequence of commands results in the same errors we see when trying to build the demo app (No module named 'gflags'). I can sort of fix this with $ pip install python-gflags, which makes Python not even try to use the local files (this seems like an ultimately buggy workaround). The import is fixed, but the build (below) is still busted with a str-to-buffer message problem which I've included at the very bottom of the issue.

Here's how I ran the TF Lite app build. The build requires the SDK setup steps for Tensorflow's WORKSPACE.

$ virtualenv --python=python3 --system-site-packages /tmp/py3
$ git clone http://github.com/tensorflow/tensorflow /tmp/tf
$ cd /tmp/tf
$ source /tmp/py3/bin/activate
# prepare WORKSPACE, see link above
$ ./configure      # should default to /tmp/py3 python path
$ bazel build //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo --cxxopt='--std=c++11' --config=android_arm 

Environment info

• Operating System: Ubuntu 14.04 LTS
• Bazel version (output of bazel info release): release 0.7.0

Have you found anything relevant by searching the web?

• #1580 seems generally relevant.
• A relevant-looking issue from rules_docker
• Building the tflite demo app from source
• Where installing python-gflags was noted
• An SO question on the str buffer error

Anything else, information or logs or outputs that would be helpful?

This incompatibility means that the TF Lite app can't be built (afaik) unless users install Python 2. Not a tremendous problem, but pretty inconvenient.

From the build commands above, I get something like this:

(py3)❯ bazel build //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo --cxxopt='--std=c++11' --config=android_arm --logging=0
WARNING: The major revision of the Android NDK referenced by android_ndk_repository rule 'androidndk' is 15. The major revisions supported by Bazel are [10, 11, 12, 13, 14]. Defaulting to revision 14.
INFO: Analysed target //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo (0 packages loaded).
INFO: Found 1 target...
ERROR: /usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/external/androidsdk/com.android.support/BUILD:4563:1: Filtering AAR native libs by architecture failed (Exit 1)
Traceback (most recent call last):
  File "/usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/execroot/org_tensorflow/bazel-out/host/bin/external/bazel_tools/tools/android/aar_native_libs_zip_creator.runfiles/org_tensorflow/../bazel_tools/tools/android/aar_native_libs_zip_creator.py", line 26, in <module>
    from third_party.py import gflags
  File "/usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/execroot/org_tensorflow/bazel-out/host/bin/external/bazel_tools/tools/android/aar_native_libs_zip_creator.runfiles/bazel_tools/third_party/py/gflags/__init__.py", line 1, in <module>
    from gflags import *
ImportError: No module named 'gflags'
Target //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.440s, Critical Path: 0.11s
FAILED: Build did NOT complete successfully

And here's the str-to-buffer problem after installing pip install python-gflags:

(py3)❯ bazel build //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo --cxxopt='--std=c++11' --config=android_arm --logging=0
WARNING: The major revision of the Android NDK referenced by android_ndk_repository rule 'androidndk' is 15. The major revisions supported by Bazel are [10, 11, 12, 13, 14]. Defaulting to revision 14.
INFO: Analysed target //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo (50 packages loaded).
INFO: Found 1 target...
ERROR: /usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/external/androidsdk/com.android.support/BUILD:4563:1: Extracting classes.jar and libs/*.jar from support-fragment-25.2.0.aar failed (Exit 1)
Traceback (most recent call last):
  File "/usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/execroot/org_tensorflow/bazel-out/host/bin/external/bazel_tools/tools/android/aar_embedded_jars_extractor.runfiles/org_tensorflow/../bazel_tools/tools/android/aar_embedded_jars_extractor.py", line 92, in <module>
    main()
  File "/usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/execroot/org_tensorflow/bazel-out/host/bin/external/bazel_tools/tools/android/aar_embedded_jars_extractor.runfiles/org_tensorflow/../bazel_tools/tools/android/aar_embedded_jars_extractor.py", line 87, in main
    _Main(FLAGS.input_aar, FLAGS.output_singlejar_param_file, FLAGS.output_dir)
  File "/usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/execroot/org_tensorflow/bazel-out/host/bin/external/bazel_tools/tools/android/aar_embedded_jars_extractor.runfiles/org_tensorflow/../bazel_tools/tools/android/aar_embedded_jars_extractor.py", line 67, in _Main
    output_dir_orig)
  File "/usr/local/google/home/angerson/.cache/bazel/_bazel_angerson/7b7f16644e8d0eb6d37d6401f95d6305/execroot/org_tensorflow/bazel-out/host/bin/external/bazel_tools/tools/android/aar_embedded_jars_extractor.runfiles/org_tensorflow/../bazel_tools/tools/android/aar_embedded_jars_extractor.py", line 48, in ExtractEmbeddedJars
    singlejar_param_file.write("--exclude_build_data\n")
TypeError: 'str' does not support the buffer interface
Target //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 10.214s, Critical Path: 0.54s
FAILED: Build did NOT complete successfully

[akirabaruah]

I think that #3855 should resolve this issue, but I'll test it to confirm.

[aj-michael]

Hey thanks for bringing this to our attention, ccing some people that can help
@jin @dkelmer @ahumesky

[akirabaruah]

Thanks @aj-michael - I was able to reproduce @angersson's errors and can confirm that #3855 resolves the first one.

However, the second error persists. It can probably be resolved by updating modules in tools/android and tools/build_defs for compatibility with python3-style strings. Should be relatively simple, so I can probably make those changes soon.

[akirabaruah]

As promised, I've created a branch containing python 3 compatibility updates to bazel tools.

@angersson @aj-michael @jin @dkelmer @ahumesky you can test the fix by running:

git clone https://github.com/akira-baruah/bazel.git /tmp/bazel-akira
cd /tmp/bazel-akira
git checkout python3-tools  # branch with bugfixes
bazel build //src:bazel

cd <tensorflow repo>
/tmp/bazel-akira/bazel-bin/src/bazel build //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo --cxxopt='--std=c++11' --force_python=py3 --python_path=$(which python3) --config=android_arm --logging=0

If it looks good to you, I'll make a PR. Please note that this branch depends on PR #3855, so we would probably want to have that merged first.

Thanks!

[angerson]

I was able to replicate the fixes, but I'll need to fetch NDK 15 to fully test building the app in a clean environment due to #4068.

[angerson]

I verified build success with nvidia-docker, gcr.io/tensorflow/tensorflow:latest-devel-gpu, and this... awful script, run inside the container:

#!/usr/bin/env bash

set -euxo pipefail

TMPDIR=$(mktemp -d)
trap '' PIPE

git clone https://github.com/akira-baruah/bazel.git ${TMPDIR}/bazel-akira
cd ${TMPDIR}/bazel-akira
git checkout python3-tools  # branch with bugfixes
bazel build //src:bazel

cd ${TMPDIR}

curl -o ${TMPDIR}/sdk-tools.zip https://dl.google.com/android/repository/sdk-tools-linux-3859397.zip
unzip ${TMPDIR}/sdk-tools.zip -d ${TMPDIR}/sdk
echo "y" | ${TMPDIR}/sdk/tools/bin/sdkmanager "build-tools;26.0.1" "platforms;android-26" "extras;android;m2repository"

pip install virtualenv
virtualenv --python=python3 --system-site-packages ${TMPDIR}/py3
PS1=""  # Avoids `set -u`-related error with bin/activate
source ${TMPDIR}/py3/bin/activate

git clone http://github.com/tensorflow/tensorflow ${TMPDIR}/tf
cd ${TMPDIR}/tf

curl -o ${TMPDIR}/ndk.zip https://dl.google.com/android/repository/android-ndk-r14b-linux-x86_64.zip
unzip ${TMPDIR}/ndk.zip -d ${TMPDIR}/ndk/

cat >> ${TMPDIR}/tf/WORKSPACE <<HEREDOC
android_sdk_repository(
    name = "androidsdk",
    api_level = 26,
    build_tools_version = "26.0.1",
    path = "${TMPDIR}/sdk",
)
android_ndk_repository(
    name="androidndk",
    path="${TMPDIR}/ndk/android-ndk-r14b",
    api_level=14)
HEREDOC

set +o pipefail
yes '' | ${TMPDIR}/tf/configure
set -o pipefail
cd ${TMPDIR}/tf
${TMPDIR}/bazel-akira/bazel-bin/src/bazel build //tensorflow/contrib/lite/java/demo/app/src/main:TfLiteCameraDemo --cxxopt='--std=c++11' --config=android_arm

Sweet.

[akirabaruah]

@angersson now that gflags supports python 3 imports (see commits fb15f0f4e4885243d354a14997d09463594385bf, d926bc40260549b997a6a5a1e82d9e7999dbb65e, and 4d0e6265911199b1376d0f52e249625180a0500d), I've created PR #4265 to resolve this issue.