Add instructions to proto package README (open-telemetry#905)

Author: aabmass

opentelemetry-proto/README.rst

@@ -16,15 +16,20 @@ Installation
 Code Generation
 ---------------
 
-These files were generated automatically. More details on how to generate them
-are available here_.
+These files were generated automatically from code in opentelemetry-proto_.
+To regenerate the code, run ``../scripts/proto_codegen.sh``.
 
+To build against a new release or specific commit of opentelemetry-proto_,
+update the ``PROTO_REPO_BRANCH_OR_COMMIT`` variable in
+``../scripts/proto_codegen.sh``. Then run the script and commit the changes
+as well as any fixes needed in the OTLP exporter.
 
-.. _here: https://github.com/open-telemetry/opentelemetry-proto
+.. _opentelemetry-proto: https://github.com/open-telemetry/opentelemetry-proto
 
 
 References
 ----------
 
 * `OpenTelemetry Project <https://opentelemetry.io/>`_
 * `OpenTelemetry Proto <https://github.com/open-telemetry/opentelemetry-proto>`_
+* `proto_codegen.sh script <https://github.com/open-telemetry/opentelemetry-python/blob/master/scripts/proto_codegen.sh>`_

scripts/proto_codegen.sh

@@ -16,16 +16,24 @@ PROTO_REPO_BRANCH_OR_COMMIT="v0.4.0"
 
 set -e
 
-if [ -z "$VIRTUAL_ENV" ]; then
-    echo '$VIRTUAL_ENV is not set, you probably forgot to source it. Exiting...'
-    exit 1
-fi
-
 PROTO_REPO_DIR=${PROTO_REPO_DIR:-"/tmp/opentelemetry-proto"}
 # root of opentelemetry-python repo
 repo_root="$(git rev-parse --show-toplevel)"
+venv_dir="/tmp/proto_codegen_venv"
+
+# run on exit even if crash
+cleanup() {
+    echo "Deleting $venv_dir"
+    rm -rf $venv_dir
+}
+trap cleanup EXIT
 
-python -m pip install -r $repo_root/dev-requirements.txt
+echo "Creating temporary virtualenv at $venv_dir using $(python3 --version)"
+python3 -m venv $venv_dir
+source $venv_dir/bin/activate
+python -m pip install \
+    -c $repo_root/dev-requirements.txt \
+    grpcio-tools mypy-protobuf
 
 # Clone the proto repo if it doesn't exist
 if [ ! -d "$PROTO_REPO_DIR" ]; then