Advanced Go

Magesh Kuppan

• [email protected]

Schedule

• Commence : 9:00 AM
• Tea Break : 10:30 AM (20 mins)
• Lunch Break : 12:30 PM (1 hr)
• Tea Break : 3:00 PM (20 mins)
• Wind up : 5:00 PM

Methodology

• No powerpoint
• Code & Discussion
• No dedicated time for Q&A

Repository

• https:/tkmagesh/cisco-advgo-may-2024

Software Requirements

• Go Tools
• Visual Studio Code
• Go extension for VS Code

Prerequisites

• Familiar with the following Go concepts
  • Data Types
  • Programming Constructs
  • Pointers
  • Error Handling
  • Functions
  • Functional Programming
    • Higher Order Functions
    • Anonymous Functions
    • Deferred Functions
  • Panic & Recovery
  • Structs & Struct Composition
  • Interfaces

Agenda

- Recap
- Concurrency
- Concurrency Patterns
- HTTP Services
- GRCP
- Testing
- Performance Enginneering
    - Microbenchmarking
    - Profiling

Recap

Higher Order Functions

• functions like data
  • Assign a function to a variable
  • Pass a function as an argument to another function
  • Return a function as a return value

Deferred Functions

• Postpone the execution of a function until the current function execution completes

Struct Composition

• Composition is how go implements "inheritance"

Concurrency

• A design methodology where the application has more than one execution path
• Typically achieved using OS theads (1 OS Thread = 2 MB)

Concurrency in Go

• Builtin Scheduler
• Concurrent operations are represented in light-weight threads call goroutines
• Goroutines are cheap (4 KB)
• Scheduler maps goroutines to OS Threads
• Language support for concurrency
  • go keyword, channel (chan) data type, channel ( <- ) operator, for range construct, select case construct
• API support
  • sync package
  • sync/atomic package

Channels

• data type for enabling communication between goroutines

Declaration

var ch chan int

Initilialization

ch = make(chan int)

Combine Declaration & Initialization

ch := make(chan int)

Channel Operations

• Using the channel operator ( <- )

Send Operation

ch <- 100

Receive Operation

data := <- ch

Channel Behavior

The first operation (send or receive) on a channel will ALWAYS be a blocking operation

Context

• Cancel Propagation across hierarchy of goroutines
• Cancellation can be
  • programmatic
  • time based
• Contexts can be created as a hierarchy
• Root context is created with 'context.Background()'
• Context factory methods:
  • context.WithTimeout()
  • context.WithDeadline()
  • context.WithCancel()
• Can also use contexts to share data across goroutines
  • context.WithValue()

Curl

curl http://localhost:8080/products

curl http://localhost:8080/products -X POST -H 'Content-Type:application/json' -d '{"name":"Scribble Pad","cost":20,"category":"Stationary"}'

GRPC

• Alternative to HTTP based restful services
• Optimal for micro-services communication
• Communication Patterns
  • Request & Response
  • Server Streaming (one request & stream of responses)
  • Client Streaming (stream of requests & one response)
  • Bidirectional Streaming (stream of requests & stream of responses)
• HTTP2
• Uses Protocol Buffers for serializing payloads
  • Protocol Buffers Reference
  • Share the schema among the consumers and producers in advance
• Multi-language supports
  • Go
  • Java
  • .NET
  • Node.js
  • Python

Steps:

- Create "service / operations / data" contracts using protocol buffers
- Share the contract between the client & server
- Generate proxy & stub using the contracts
- Server
    - implement the service (with the business logic) based on the contract
    - host the service
- Client
    - Use the proxy to communicate to the service

Tools Installation

1. Protocol Buffers Compiler (protoc tool)
    Windows:
        Download the file, extract and keep in a folder (PATH) accessble through the command line
        https:/protocolbuffers/protobuf/releases/download/v24.4/protoc-24.4-win64.zip
    Mac:
        brew install protobuf

    Verification:
        protoc --version

2. Go plugins (installed in the GOPATH/bin folder)
    go install google.golang.org/protobuf/cmd/[email protected]
    go install google.golang.org/grpc/cmd/[email protected]

Benchmarking

go test -run=^$ -bench ./...

Profiling

Reference

Testing

• gotest tool (https:/rakyll/gotest)
• To generate mock objects (https://vektra.github.io/mockery/latest/)