DDIA Chapter 4: In the (proto)Buff

Install grpcio-tools:

pip install -r requirements.txt

Generate both RPC stubs + protobuf classes:

python -m grpc_tools.protoc -I. --python_out=. --pyi_out=. --grpc_python_out=. ./post.proto

Docker setup

1. Install Dev Containers VS Code extension: https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers
2. Build the image: docker build -t ddia-4 .
3. Run the image: docker run -it ddia-4
4. Click the "remote" icon in the bottom left of VS Code, then select "Attach to Running Container" and select the ddia-4 container you just ran

Next Steps

1. Run python server.py and python client.py (in separate terminals) to create some posts — check out posts.db and/or posts.json to see the encoded data
2. Add comments (either as nested objects with Post or separate Comment type) + create/read RPCs
3. Some ideas for schema evolution (make sure to regenerate the protobuf classes after each change):

• Try changing Post.id from an int32 to a string (what happens with old encoded Posts when the server deserializes them?)
• Mark Post.id as reserved, then add a new string uuid field instead
• Change Post.views to a uint64
• Relevant docs for updating and reserved

4. Try a "rolling upgrade" for a backward-compatible change:

• Leave the server/client running
• Change the Post schema in post.proto
• Regenerate the protobuf classes
• Make code changes for the new fields
• Run the server/client again on a different port

References

• https://grpc.io/docs/languages/python/basics/
• https://developers.google.com/protocol-buffers/docs/pythontutorial
• https://developers.google.com/protocol-buffers/docs/proto3

Old commands just for generating protobuf classes

Just use above

Install protoc:

apt-get install protobuf-compiler

Generate post_pb2.py from post.proto:

protoc --python_out=. ./post.proto