Author: Thomas Ferreira de Lima
email: thomas@tlima.me

I wrote these notes as I was learning how to use docker and how to build python packages inside a docker image prepared by the pypa team. They require us to build there to allow wheels to have the `manylinux1` tag, meaning that these wheels would be compatible with most linux distributions around. Chapter 1 is about testing in my own computer (MacOS Mojave) and Chapter 2 is about how to automate this build using travis-ci.org.

# Chapter 1. Testing on your own computer
## Step 1.

Make sure you have the quay.io/pypa/manylinux1_x86_64 image.

```bash
$ docker images
REPOSITORY                       TAG                 IMAGE ID            CREATED             SIZE
quay.io/pypa/manylinux1_x86_64   latest              1c8429c548f2        2 months ago        879MB
hello-world                      latest              4ab4c602aa5e        3 months ago        1.84kB
# My image was old:
$ docker pull quay.io/pypa/manylinux1_x86_64
Using default tag: latest
latest: Pulling from pypa/manylinux1_x86_64
7d0d9526f38a: Already exists
3324bfadf9cb: Pull complete
20f27c7e3062: Pull complete
5bc21fc5fe97: Pull complete
Digest: sha256:a13b2719fb21daebfe25c0173d80f8a85a2326dd994510d7879676e7a2193500
Status: Downloaded newer image for quay.io/pypa/manylinux1_x86_64:latest
```

## Step 2.

This step was inspired by https://dev.to/jibinliu/how-to-persist-data-in-docker-container-2m72
Create a volume for klayout. This is necessary because docker containers don't persist data.

```bash
$ docker volume create klayout-persist
$ docker volume inspect klayout-persist
[
    {
        "CreatedAt": "2018-12-18T15:01:48Z",
        "Driver": "local",
        "Labels": {},
        "Mountpoint": "/var/lib/docker/volumes/klayout-persist/_data",
        "Name": "klayout-persist",
        "Options": {},
        "Scope": "local"
    }
]
```

## Step 3.

Build image `myimage` with:

```bash
$ docker build -t myimage:latest -f Dockerfile.x86_64 .
```

This creates an image called `myimage` (temporary). This image will not overwrite old ones. Tip: prune old, unused images with `docker image prune`.

Then I run the docker with a terminal shell and load the volume klayout-persist in /persist:

```bash
$ docker run --name klayout --mount source=klayout-persist,target=/persist -it myimage
```

## Step 4.

In the shell, pull master from klayout.

```bash
cd /persist
git clone https://github.com/lightwave-lab/klayout.git
mkdir -p wheelhouse
cd klayout
# make wheel with python 3.6 (for example)
/opt/python/cp36-cp36m/bin/python setup.py bdist_wheel -d /persist/wheelhouse/
cd /persist
auditwheel repair "wheelhouse/klayout-0.26.0.dev8-cp36-cp36m-linux_x86_64.whl" -w wheelhouse/
# Need to manually fix the wheel
#/opt/python/cp36-cp36m/bin/pip install klayout --no-index -f /wheelhouse
```

The produced wheel from auditwheel, klayout-0.26.0.dev8-cp36-cp36m-manylinux1_x86_64.whl, is defective in the following way: dbcore.so etc. have RPATHs reset to `$ORIGIN/.libs`, so we need to move all .so's `lib_*` into `.libs`, as well as `db_plugins`. We also need to change the dist-info/RECORD file paths. This is a bug from auditwheel, it should either have added a new RPATH, $ORIGIN/.libs, where it places libz, libcurl, libexpat, instead of renaming the existing ones, or moved the files to the right place.


Procedure to fix the wheel:

```bash
unzip wheelhouse/klayout-0.26.0.dev8-cp36-cp36m-manylinux1_x86_64.whl -d tempwheel
cd tempwheel/klayout
mv lib_* db_plugins .libs/
cd ../klayout-0.26.0.dev8.dist-info/
sed -i 's/^klayout\/lib_/klayout\/.libs\/lib_/g' RECORD
sed -i 's/^klayout\/db_plugins/klayout\/.libs\/db_plugins/g' RECORD
cd ../
rm -f ../wheelhouse/klayout-0.26.0.dev8-cp36-cp36m-manylinux1_x86_64.whl
zip -r ../wheelhouse/klayout-0.26.0.dev8-cp36-cp36m-manylinux1_x86_64.whl ./*
cd ..
rm -rf tempwheel
```

Now we can install and test:
```bash
/opt/python/cp36-cp36m/bin/pip install klayout --no-index -f /persist/wheelhouse
cd /persist/klayout
/opt/python/cp36-cp36m/bin/python -m unittest testdata/pymod/import_db.py  testdata/pymod/import_rdb.py testdata/pymod/import_tl.py
# Tests passed!
```

Encoded this behavior in a script called fix_wheel.sh. now you only need to run `./fix_wheel.sh wheelhouse/klayout-0.26.0.dev8-cp36-cp36m-manylinux1_x86_64.whl`, and it will overwrite the wheel.

## Step 5. Iterate over all python versions.

For that, we need something like:

```bash
# Compile wheels
for PYBIN in /opt/python/*/bin; do
    "${PYBIN}/python" setup.py bdist_wheel -d /persist/wheelhouse/
done

# Bundle external shared libraries into the wheels via auditwheel
for whl in /persist/wheelhouse/*linux_*.whl; do
    auditwheel repair "$whl" -w /persist/wheelhouse/
done

# Fix each wheel generated by auditwheel
for whl in /persist/wheelhouse/*manylinux1_*.whl; do
    ./ci-scripts/docker/fix_wheel.sh "$whl"
done

# Install packages and test
TEST_HOME=/persist/klayout/testdata
for PYBIN in /opt/python/*/bin/; do
    "${PYBIN}/pip" install klayout --no-index -f /persist/wheelhouse
    "${PYBIN}/python" $TEST_HOME/pymod/import_db.py  
    "${PYBIN}/python" $TEST_HOME/pymod/import_rdb.py 
    "${PYBIN}/python" $TEST_HOME/pymod/import_tl.py

```

I tested step 1-5 with both quay.io/pypa/manylinux1_x86_64 and quay.io/pypa/manylinux1_i686. So far the only failure was with `cp27-cp27mu` which gave this import error:

`ImportError: /opt/python/cp27-cp27mu/lib/python2.7/site-packages/klayout/.libs/lib_pya.so: undefined symbol: PyUnicodeUCS2_AsUTF8String`

I noticed that the ccache folder ended up with 800MB. I was hoping that the gcc compilation could reuse a lot of previously built objects but that didn't happen. I think that's because each python comes with its own header. So going forward it doesn't make sense to create a docker image for every python version. I will just cache a ccache folder via travis.
The ccache folder after a single build has 657MB. Go figure.

I discovered that fix_wheel script was actually not properly working. So instead I looked into fixing `auditwheel` directly. Here's the commit that fixes it: https://github.com/thomaslima/auditwheel/tree/87f5306ec02cc68020afaa9933543c898b1d47c1

So now the plan is to change the `docker_build.sh` script so it uses the proper auditwheel, instead of their default.

# Chapter 2. Testing CI flow with docker

# Step 1. Testing commands in own computer

First cloned with:
```bash
git clone git@github.com:lightwave-lab/klayout.git -b tmp/manylinux
cd klayout
```

Let's work with a few environment variables, like in https://github.com/pypa/python-manylinux-demo/blob/master/.travis.yml

DOCKER_IMAGE options: quay.io/pypa/manylinux1_x86_64 quay.io/pypa/manylinux1_i686

PY_VERSION options: cp27-cp27m  cp27-cp27mu  cp34-cp34m  cp35-cp35m  cp36-cp36m  cp37-cp37m

Total of 2x6 = 12 possibilities

```bash
export DOCKER_IMAGE=quay.io/pypa/manylinux1_x86_64
export PY_VERSION="cp36-cp36m"
docker pull $DOCKER_IMAGE
mkdir -p ccache
mkdir -p wheelhouse
docker run --name klayout -v `pwd` -it $DOCKER_IMAGE
```

Inside docker shell:
```bash
yum install -y zlib-devel
yum install -y zip

yum install -y ccache
ln -s /usr/bin/ccache /usr/lib64/ccache/c++
ln -s /usr/bin/ccache /usr/lib64/ccache/cc
ln -s /usr/bin/ccache /usr/lib64/ccache/gcc
ln -s /usr/bin/ccache /usr/lib64/ccache/g++
echo $PATH
# /usr/lib64/ccache:/opt/rh/devtoolset-2/root/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export CCACHE_DIR="/io/ccache"

# Compile wheel
/opt/python/$PY_VERSION/bin/python setup.py bdist_wheel -d /io/wheelhouse/

# Bundle external shared libraries into the wheels via auditwheel
for whl in /io/wheelhouse/*linux_*.whl; do
    auditwheel repair "$whl" -w /io/wheelhouse/
done

# Fix each wheel generated by auditwheel
for whl in /io/wheelhouse/*manylinux1_*.whl; do
    ./ci-scripts/docker/fix_wheel.sh "$whl"
done

```

# Step 2. Automating step 1 in travis (CI).
DOCKER_IMAGE options: quay.io/pypa/manylinux1_x86_64 quay.io/pypa/manylinux1_i686

PY_VERSION options: cp27-cp27m  cp27-cp27mu  cp34-cp34m  cp35-cp35m  cp36-cp36m  cp37-cp37m

Build: spawn 12 travis jobs, one for each combination of word-size and python version. 
Output: populated ./ccache with compiled objects and wheels inside ./wheelhouse/, one useless, `*linux_*.whl` and one useful `*manylinux1_*.whl`.
Post-build: 
- cache `./ccache`
- deploy `./wheelhouse/*manylinux1_*.whl` to dropbox (./deploy folder)

# Step 3. Automating deployment to PyPI:

TBD