Advanced Go

Magesh Kuppan

• [email protected]

Schedule

• Commence : 09:00 AM
• Tea Break : 10:30 AM (20 mins)
• Lunch Break : 12:30 PM (1 hr)
• Tea Break : 03:00 PM (20 mins)
• Wind up : 05:00 PM

Methodology

• No powerpoint presentation
• Discuss & Code
• No dedicated time for Q&A

Repository

• https://github.com/tkmagesh/cisco-advgo-jul-2024

Prerequisites

• Programming Constructs
• Higher Order Functions
• Error Handling
• Panic & Recovery
• Structs & Methods
• Struct Composition
• Interfaces
• Modules & Packages
• Concurrency (Optional)

Software Requirements

• Go tools
• Any editor (Visual Studio Code)
• Docker Desktop (Optional)

Review

• Higher Order Functions
• Interfaces
• Struct Composition
• Deferred Functions
• Panic & Recovery

Higher Order Functions

• Assign functions to variables
• Pass functions as arguments
• Return a function as a return value

Concurrency

• Ability to have more than one execution path
• Typically achieved using OS Threads
  • OS Threads are costly
    • ~2 MB of Memory (in linux)
    • Mitigate the cost of creating/destroying threads using thread pools

Go Concurrency

• Concurrent operations are represented as "goroutines"
• goroutines are cheap (~4KB)
• Builtin scheduler
  • Go scheduler schedules the goroutine executions through the OS threads
• Concurrency support is built in the language itself
  • go keyword, channel data type, channel operator ( <- ), for-range, select-case
  • APIs support
    • "sync" package
    • "sync/atomic" package

WaitGroup ("sync" package)

• semaphore based counter
• has the capability to block the execution of the current function until the counter becomes 0

Data Race

go run --race [filename.go]

go build --race [filename.go]

Channels

Declaration

var [var_name] chan [data_type]
// ex:
var ch chan int

Instantiation

[var_name] = make(chan [data_type])
// ex:
ch = make(chan int)

Combine Declaration & Instantiation

ch := make(chan int)

Channel Operations

• using the channel operator ( <- )

Send Operation

[channel_var_name] <- [data]
// ex:
ch <- 100

Receive Operation

<-[channel_var_name]
// ex:
data := <-ch

Channel Behavior

• "Receive" operation is ALWAYS a blocking operation
• A "Send" operation is blocked until a "Receive" operation a initiated (conditional)

Context

• API for "cancellation" propagation
• context.Background() (used to create the top-most context and this is non-cancellable)
• Context creation apis
  • context.WithCancel()
    • programmatic cancellation
  • context.WithTimeout()
    • Will automatically do cancellation based on the elapsed time
    • Wrapper for context.WithDeadline()
  • context.WithDeadline()
    • Will automatically do cancellation based on the absolute date & time
  • context.WithValue()
    • Used to share data through context hierarchy
    • Does not offer cancellation functionality

HTTP Service

net/http package

• Both http client & server apis

Routing Libraries

Web Frameworks

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)
• Use 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 / Operation / Data" contracts using protocol buffers
• Share the schema between the server & client
• Generate the proxy & stub using the schema client -> proxy -> stub -> service
• Implement & Host the server
• Use the proxy to communicate to the server

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://github.com/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]

Testing

• gotest - https://github.com/rakyll/gotest
• mockery - https://vektra.github.io/mockery/latest/
• testify - https://github.com/stretchr/testify

Run Tests

• go test ./... -v

Profiling

go test -run=^$ -bench=. ./... -cpu=1,2,4,8 -benchmem

CPU profiling

go test -run=^$ -bench=. ./... -cpuprofile=cpu.prof -cpu=1,2,4,8 -benchmem

Memory profiling

go test -run=^$ -bench=. ./... -memprofile=mem.prof -cpu=1,2,4,8 -benchmem

Analysing profile data

go tool pprof <profile_file>

pprof commands

• top10
• list <function_name>
• web