proto

About Proto

What are we doing with protobuf?

here we are using proto to define out data schema for communication

• we will define out entites // and the contract for the api //
• we will use protoc // protocompiler to generate GO's representation for the proto contract/entities
• then we will test the go files generated // that its actually working in a go program

What do we write in a proto file?

• write syntax to mention what proto version we are using

• write the packageing scheme for our proto contracts (refer the practice folder for the scheme that you can follow to define multiple message contracts)

• mention the go package you want the generated go classes to have (so that they can be imported in go program with ease)

  • use the options flag go_package variable to let the protoc compiler know that /// thats the go pacakge value to be embedded in generate go files

• define the messages (entities/classes types for go program)

• define the service (apis for grpc)

How to make protoc compile proto contracts and create files/models/services that we can use in our app

command goes like this

protoc -Igreet/proto --go_opt=module=github.com/amogh2019/dummy_go_service --go_out=. greet/proto/*.proto

• we run this at directory root
• -I tells compiler where to find the proto files to generate
• go_opt tells that we have some custom flags to honor while generating go code
• go_opt_module tells that which go module to place generated files in
• go_out tells the relative path to the go module to place the generated files in
• {greet/proto/*.proto} would be the specific files to compile

Some more protoc compiler feature

• Since serialized proto is binary and not human read friendly, we can ask the compiler to decode it into tag:value wala human friendly readable print

  • cat ./greet/server/practice/messageInSerializedForm.bin | protoc --decode_raw

  1: 20
  2: 1
  3: "Dummy21"
  4: "hoyee"
  4: "dumm"
  4: "sdfsadf"
  

• we can also ask the compiler to read the binary and parse into a specific proto

  • uss proto file ke uss message mein parse karo
  • standard input read karna hota hai usse, issliye example ke liye pipe karke input diya
  • cat ./greet/server/practice/messageInSerializedForm.bin | protoc --decode=greet.practice.level3.SampleMessage greet/proto/practice/level3/sample1.proto

  id: 20
  is_active: true
  name: "Dummy21"
  alt_names: "hoyee"
  alt_names: "dumm"
  alt_names: "sdfsadf"
  

• we can also encode the proto human friendly readable format into proto binary format

  • cat ./greet/server/practice/messageInProtoHumanFriendly.txt | protoc --encode=greet.practice.level3.SampleMessage greet/proto/practice/level3/sample1.proto > temp.bin

About updating proto messages

• thoda dekh ke karna // sirf name changes mein no worries
• type change for a field mein issues ho skte // backward compatablity mein // pura data might break while deserializtion
• field ka tag change can also mess things up // since tag is the identifier (and tag+type is encoded in binary) in the actual binary form // fieldname is just a label
• tags update kar rahe toh future incremental tag dedo // aur purane ko block kardo
  • use reserved keyword // block tag and fieldname both