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dtctl Architecture Proposal

Executive Summary

This document proposes a Go-based architecture for dtctl, leveraging the same technology stack as kubectl. Go provides excellent CLI tooling, cross-platform compilation, and a mature ecosystem for building robust command-line applications.

Technology Stack

Core Language: Go 1.24+

Rationale:

  • kubectl compatibility: Uses the same language and many of the same libraries as kubectl
  • Single binary distribution: Compiles to a single, statically-linked binary with no runtime dependencies
  • Cross-platform: Native compilation for Linux, macOS, Windows (AMD64, ARM64)
  • Performance: Fast startup time, low memory footprint
  • Strong ecosystem: Excellent libraries for CLI development, HTTP clients, and OpenAPI
  • Concurrency: Built-in goroutines for parallel operations (e.g., fetching multiple resources)

CLI Framework: Cobra + Viper

Cobra (Command Structure)

Repository: https://github.com/spf13/cobra

Features:

  • Hierarchical command structure (verb-noun pattern)
  • Automatic help generation
  • Shell completion (bash, zsh, fish, powershell)
  • Persistent and local flags
  • Aliases and command suggestions
  • Used by: kubectl, GitHub CLI, Hugo, Docker CLI

Usage:

// Root command
rootCmd := &cobra.Command{
    Use:   "dtctl",
    Short: "Dynatrace platform CLI",
}

// Subcommands
getCmd := &cobra.Command{Use: "get"}
applyCmd := &cobra.Command{Use: "apply"}

// Resource-specific commands
getDocumentsCmd := &cobra.Command{
    Use:     "documents [id]",
    Aliases: []string{"document", "doc"},
    Run:     getDocumentsHandler,
}

Viper (Configuration Management)

Repository: https://github.com/spf13/viper

Features:

  • Configuration file support (YAML, JSON, TOML)
  • Environment variable binding
  • Default values
  • Live watching and re-reading of config files
  • Reading from remote config systems (optional)

Usage:

// Load config following XDG Base Directory spec
// $XDG_CONFIG_HOME/dtctl/config (default: ~/.config/dtctl/config)
viper.SetConfigName("config")
viper.AddConfigPath(config.ConfigDir())

// Bind flags to config
viper.BindPFlag("context", cmd.Flags().Lookup("context"))

Watch Mode: Real-time Resource Monitoring

Package: pkg/watch

Architecture:

  • Watcher: Core polling engine with configurable intervals (minimum 1s, default 2s)
  • Differ: Change detection algorithm using map-based comparison
  • WatchPrinter: Output formatter with kubectl-style change indicators

Features:

  • Incremental change display (additions, modifications, deletions)
  • Graceful shutdown on Ctrl+C via context cancellation
  • Error handling for transient failures, rate limiting, and network issues
  • Memory-efficient (only stores last state, not full history)
  • Works with all get commands and DQL queries

Change Indicators:

  • + (green) for added resources
  • ~ (yellow) for modified resources
  • - (red) for deleted resources

Flags:

  • --watch: Enable watch mode
  • --interval: Polling interval (default: 2s, min: 1s)
  • --watch-only: Skip initial state display

API Client Generation: OpenAPI Generator + oapi-codegen

oapi-codegen

Repository: https://github.com/deepmap/oapi-codegen

Rationale:

  • Type-safe API clients
  • Supports all HTTP methods and authentication schemes
  • Generates models for request/response bodies
  • Lightweight generated code

Alternative considered: go-swagger (more heavyweight, OpenAPI 2.0 focused)

HTTP Client: Standard library + Resty

Resty

Repository: https://github.com/go-resty/resty

Features:

  • Built on top of Go's standard net/http
  • Automatic retry with exponential backoff
  • Request/response middleware
  • Debug logging
  • Multipart form data
  • Automatic marshaling/unmarshaling

Usage:

client := resty.New().
    SetBaseURL(baseURL).
    SetAuthToken(token).
    SetRetryCount(3).
    SetRetryWaitTime(1 * time.Second).
    SetRetryMaxWaitTime(10 * time.Second).
    AddRetryCondition(func(r *resty.Response, err error) bool {
        return r.StatusCode() == 429 // Retry on rate limit
    })

Output Formatting

Table Output: tablewriter or pterm

Repository:

Features:

  • ASCII table formatting
  • Column alignment
  • Header formatting
  • Border customization
  • Color support (pterm)

Usage:

table := tablewriter.NewWriter(os.Stdout)
table.SetHeader([]string{"Name", "Type", "Owner", "Modified"})
table.AppendBulk(rows)
table.Render()

JSON/YAML: Standard library + yaml.v3

Packages:

  • encoding/json (standard library)
  • gopkg.in/yaml.v3 for YAML

JSONPath: kubernetes/client-go JSONPath

Repository: Part of k8s.io/client-go

Features:

  • kubectl-compatible JSONPath syntax
  • Field selection from structured output

Color Control: NO_COLOR standard

Standard: no-color.org

Decision logic:

Color enabled = NOT (NO_COLOR is set) AND NOT (--plain flag) AND (stdout is a TTY OR FORCE_COLOR=1)

Implementation (pkg/output/styles.go):

  • ColorEnabled() — returns whether ANSI color output is enabled (cached with sync.Once)
  • Colorize(text, colorCode) — wraps text in ANSI escape codes only when color is enabled
  • ColorCode(code) — returns the ANSI code string or empty string when color is disabled
  • ResetColorCache() — resets the sync.Once cache (for testing only)
  • TTY detection uses golang.org/x/term.IsTerminal()

Environment variables:

  • NO_COLOR (any non-empty value) — disables color output
  • FORCE_COLOR=1 — overrides TTY detection to force color on

Context Management: Similar to kubeconfig

Implementation:

  • YAML-based configuration file
  • Store contexts, environments, tokens
  • Current context pointer
  • Use gopkg.in/yaml.v3 for serialization

Structure:

type Config struct {
    APIVersion     string              `yaml:"apiVersion"`
    Kind           string              `yaml:"kind"`
    CurrentContext string              `yaml:"current-context"`
    Contexts       []NamedContext      `yaml:"contexts"`
    Tokens         []NamedToken        `yaml:"tokens"`
    Preferences    Preferences         `yaml:"preferences"`
}

type NamedContext struct {
    Name    string  `yaml:"name"`
    Context Context `yaml:"context"`
}

type Context struct {
    Environment string `yaml:"environment"`
    TokenRef    string `yaml:"token-ref"`
}

XDG Directory Structure:

dtctl follows the XDG Base Directory Specification using the github.com/adrg/xdg library for cross-platform compatibility:

  • Config Directory: Stores configuration files

    • Linux: $XDG_CONFIG_HOME/dtctl (default: ~/.config/dtctl)
    • macOS: ~/Library/Application Support/dtctl
    • Windows: %LOCALAPPDATA%\dtctl

  • Data Directory: For application data (query libraries, templates)

    • Linux: $XDG_DATA_HOME/dtctl (default: ~/.local/share/dtctl)
    • macOS: ~/Library/Application Support/dtctl
    • Windows: %LOCALAPPDATA%\dtctl

  • Cache Directory: For temporary cached data

    • Linux: $XDG_CACHE_HOME/dtctl (default: ~/.cache/dtctl)
    • macOS: ~/Library/Caches/dtctl
    • Windows: %LOCALAPPDATA%\dtctl

Validation: validator + custom logic

Repository: https://github.com/go-playground/validator

Features:

  • Struct field validation
  • Custom validation functions
  • OpenAPI schema validation

Testing

Unit Testing: Standard library testing package

import "testing"

func TestGetDocuments(t *testing.T) {
    // Test implementation
}

HTTP Mocking: httptest (standard library)

server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    w.WriteHeader(http.StatusOK)
    json.NewEncoder(w).Encode(mockResponse)
}))
defer server.Close()

Additional Tools:

  • testify: Assertions and mocking - https://github.com/stretchr/testify
  • gomock: Mock generation - https://github.com/golang/mock
  • Golden (snapshot) tests: Output formatters are covered by golden-file tests in pkg/output/golden_test.go — uses real production structs from pkg/resources/* to capture exact output across all formats (table, wide, JSON, YAML, CSV, agent, watch, chart). Update with make test-update-golden or go test ./pkg/output/ -run TestGolden -update.

Error Handling: cockroachdb/errors

Repository: https://github.com/cockroachdb/errors

Features:

  • Error wrapping with context
  • Stack traces
  • Error formatting
  • Compatible with standard errors package
  • Better than pkg/errors (archived)

Usage:

if err != nil {
    return errors.Wrap(err, "failed to fetch document")
}

// Exit codes
const (
    ExitSuccess           = 0
    ExitError             = 1
    ExitUsageError        = 2
    ExitAuthError         = 3
    ExitNotFoundError     = 4
    ExitPermissionError   = 5
)

Logging: logrus or zap

logrus (simpler)

Repository: https://github.com/sirupsen/logrus

Features:

  • Structured logging
  • Multiple log levels
  • Pluggable formatters
  • Hooks for log routing

zap (faster, more complex)

Repository: https://go.uber.org/zap

Features:

  • Extremely fast
  • Structured and leveled logging
  • Zero-allocation in hot paths

Recommendation: Start with logrus, migrate to zap if performance becomes an issue

Build & Distribution

Build Tool: Goreleaser

Repository: https://goreleaser.com/

Features:

  • Cross-platform builds
  • Archive creation (tar.gz, zip)
  • Homebrew tap generation
  • Docker image builds
  • GitHub/GitLab release creation
  • Checksums and signing

Configuration:

# .goreleaser.yml
builds:
  - id: dtctl
    binary: dtctl
    goos:
      - linux
      - darwin
      - windows
    goarch:
      - amd64
      - arm64
    env:
      - CGO_ENABLED=0
    ldflags:
      - -s -w
      - -X main.version={{.Version}}
      - -X main.commit={{.Commit}}
      - -X main.date={{.Date}}

archives:
  - format: tar.gz
    format_overrides:
      - goos: windows
        format: zip

brews:
  - name: dtctl
    repository:
      owner: your-org
      name: homebrew-tap
    description: "Dynatrace platform CLI"
    homepage: "https://github.com/your-org/dtctl"

Package Managers:

  • Homebrew: Auto-generated via goreleaser
  • apt/yum: DEB/RPM packages via goreleaser
  • Scoop: Windows package manager
  • Docker: Container image for CI/CD usage

Shell Completion: Cobra built-in

Generation:

// Cobra provides built-in completion
rootCmd.CompletionCmd()

Installation:

# bash
dtctl completion bash > /etc/bash_completion.d/dtctl

# zsh
dtctl completion zsh > "${fpath[1]}/_dtctl"

# fish
dtctl completion fish > ~/.config/fish/completions/dtctl.fish

Update Mechanism: self-update

Repository: https://github.com/rhysd/go-github-selfupdate

Features:

  • Check for new releases
  • Download and replace binary
  • Verify checksums
  • GitHub Releases integration

Usage:

dtctl version --check-update
dtctl update

Project Structure

dtctl/
├── cmd/
│   ├── root.go                 # Root command
│   ├── get.go                  # Get command
│   ├── describe.go             # Describe command
│   ├── create.go               # Create command
│   ├── delete.go               # Delete command
│   ├── apply.go                # Apply command
│   ├── patch.go                # Patch command
│   ├── edit.go                 # Edit command
│   ├── logs.go                 # Logs command
│   ├── exec.go                 # Exec command
│   ├── label.go                # Label command
│   ├── wait.go                 # Wait command
│   ├── diff.go                 # Diff command
│   ├── explain.go              # Explain command
│   ├── config.go               # Config command
│   ├── auth.go                 # Auth command
│   ├── completion.go           # Shell completion
│   └── version.go              # Version command
│
├── pkg/
│   ├── api/                    # Generated API clients
│   │   ├── document/           # Document API client
│   │   ├── slo/                # SLO API client
│   │   ├── automation/         # Automation API client
│   │   ├── grail/              # Grail API clients
│   │   ├── iam/                # IAM API client
│   │   └── ...                 # Other API clients
│   │
│   ├── client/                 # Core API client logic
│   │   ├── client.go           # Base client with auth, retry
│   │   ├── pagination.go       # Pagination helpers
│   │   ├── rate_limit.go       # Rate limiting
│   │   └── errors.go           # Error handling
│   │
│   ├── config/                 # Configuration management
│   │   ├── config.go           # Config structure
│   │   ├── context.go          # Context management
│   │   ├── loader.go           # Config loading
│   │   └── writer.go           # Config writing
│   │
│   ├── resources/              # Resource handlers
│   │   ├── document/           # Document resource
│   │   │   ├── get.go
│   │   │   ├── create.go
│   │   │   ├── update.go
│   │   │   ├── delete.go
│   │   │   └── share.go
│   │   ├── slo/                # SLO resource
│   │   ├── workflow/           # Workflow resource
│   │   └── ...                 # Other resources
│   │
│   ├── output/                 # Output formatting
│   │   ├── table.go            # Table formatter
│   │   ├── json.go             # JSON formatter
│   │   ├── yaml.go             # YAML formatter
│   │   ├── jsonpath.go         # JSONPath formatter
│   │   ├── styles.go           # Color control (ColorEnabled, Colorize, ColorCode)
│   │   ├── agent.go            # Agent output envelope
│   │   └── printer.go          # Printer interface
│   │
│   ├── manifest/               # Manifest parsing
│   │   ├── parser.go           # YAML/JSON manifest parser
│   │   ├── validator.go        # Manifest validation
│   │   └── applier.go          # Apply logic (create/update)
│   │
│   ├── diff/                   # Diff implementation
│   │   └── diff.go             # Resource diffing logic
│   │
│   ├── watch/                  # Watch implementation
│   │   └── watch.go            # Resource watching
│   │
│   ├── exec/                   # Exec implementations
│   │   ├── dql.go              # DQL query executor
│   │   ├── workflow.go         # Workflow executor
│   │   ├── slo.go              # SLO evaluator
│   │   ├── function.go         # Function executor
│   │   └── intent.go           # Intent URL generator
│   │
│   └── util/                   # Utilities
│       ├── editor.go           # Interactive editor
│       ├── prompt.go           # User prompts
│       ├── selector.go         # Label selector parsing
│       └── version.go          # Version comparison
│
├── scripts/                    # Build and dev scripts
│   └── build.sh                # Build script
│
├── test/                       # Integration tests
│   ├── fixtures/               # Test fixtures
│   └── e2e/                    # End-to-end tests
│
├── .goreleaser.yml             # Release configuration
├── Makefile                    # Build automation
├── go.mod                      # Go module definition
├── go.sum                      # Dependency checksums
├── main.go                     # Entry point
├── README.md
├── API_DESIGN.md
├── ARCHITECTURE.md
└── AGENTS.md

Dependency Management

Go Modules

Use Go modules (go.mod) for dependency management:

module github.com/yourorg/dtctl

go 1.24

require (
    github.com/spf13/cobra v1.8.0
    github.com/spf13/viper v1.18.0
    github.com/go-resty/resty/v2 v2.11.0
    github.com/olekukonko/tablewriter v0.0.5
    gopkg.in/yaml.v3 v3.0.1
    github.com/cockroachdb/errors v1.11.1
    github.com/sirupsen/logrus v1.9.3
    github.com/go-playground/validator/v10 v10.16.0
    github.com/stretchr/testify v1.8.4
    k8s.io/client-go v0.29.0
)

Build System: Makefile

.PHONY: all build clean test generate install

VERSION ?= $(shell git describe --tags --always --dirty)
COMMIT ?= $(shell git rev-parse --short HEAD)
DATE ?= $(shell date -u +"%Y-%m-%dT%H:%M:%SZ")

LDFLAGS = -ldflags "-X main.version=$(VERSION) -X main.commit=$(COMMIT) -X main.date=$(DATE) -s -w"

all: build

# Build the binary
build:
	@echo "Building dtctl..."
	@go build $(LDFLAGS) -o bin/dtctl .

# Run tests
test:
	@echo "Running tests..."
	@go test -v -race -coverprofile=coverage.out ./...

# Install locally
install:
	@echo "Installing dtctl..."
	@go install $(LDFLAGS) .

# Clean build artifacts
clean:
	@rm -rf bin/ dist/ coverage.out

# Run linter
lint:
	@golangci-lint run

# Format code
fmt:
	@go fmt ./...
	@goimports -w .

# Release (using goreleaser)
release:
	@goreleaser release --clean

# Release snapshot (local testing)
release-snapshot:
	@goreleaser release --snapshot --clean

Development Workflow

1. Development Setup

# Clone repository
git clone https://github.com/yourorg/dtctl.git
cd dtctl

# Install dependencies
go mod download

# Build
make build

# Run tests
make test

2. CI/CD Pipeline (GitHub Actions)

# .github/workflows/ci.yml
name: CI

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-go@v5
        with:
          go-version: '1.24'

      - name: Install dependencies
        run: go mod download

      - name: Run tests
        run: make test

      - name: Run linter
        run: make lint

      - name: Build
        run: make build

  release:
    runs-on: ubuntu-latest
    if: startsWith(github.ref, 'refs/tags/')
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-go@v5
        with:
          go-version: '1.24'

      - name: Run GoReleaser
        uses: goreleaser/goreleaser-action@v5
        with:
          version: latest
          args: release --clean
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

Core Implementation Patterns

1. Command Pattern

// cmd/get.go
package cmd

import (
    "github.com/spf13/cobra"
    "github.com/yourorg/dtctl/pkg/resources"
)

var getCmd = &cobra.Command{
    Use:   "get [resource]",
    Short: "Display one or many resources",
}

var getDocumentsCmd = &cobra.Command{
    Use:     "documents [id]",
    Aliases: []string{"document", "doc"},
    Short:   "Get documents",
    RunE:    runGetDocuments,
}

func runGetDocuments(cmd *cobra.Command, args []string) error {
    cfg, err := config.Load()
    if err != nil {
        return err
    }

    client := client.NewFromConfig(cfg)
    handler := resources.NewDocumentHandler(client)

    opts := resources.GetOptions{
        Output:    cmd.Flags().GetString("output"),
        Selector:  cmd.Flags().GetString("selector"),
    }

    if len(args) > 0 {
        return handler.Get(args[0], opts)
    }
    return handler.List(opts)
}

func init() {
    getCmd.AddCommand(getDocumentsCmd)
    rootCmd.AddCommand(getCmd)

    // Add flags
    getDocumentsCmd.Flags().StringP("output", "o", "table", "Output format")
    getDocumentsCmd.Flags().StringP("selector", "l", "", "Label selector")
}

2. Resource Handler Pattern

// pkg/resources/document/handler.go
package document

import (
    "context"
    "github.com/yourorg/dtctl/pkg/api/document"
    "github.com/yourorg/dtctl/pkg/output"
)

type Handler struct {
    client *document.Client
}

func NewHandler(client *document.Client) *Handler {
    return &Handler{client: client}
}

func (h *Handler) Get(id string, opts GetOptions) error {
    ctx := context.Background()

    doc, err := h.client.GetDocument(ctx, id)
    if err != nil {
        return errors.Wrap(err, "failed to get document")
    }

    printer := output.NewPrinter(opts.Output)
    return printer.Print(doc)
}

func (h *Handler) List(opts ListOptions) error {
    ctx := context.Background()

    params := &document.ListDocumentsParams{
        Owner: opts.Owner,
        Type:  opts.Type,
    }

    docs, err := h.client.ListDocuments(ctx, params)
    if err != nil {
        return errors.Wrap(err, "failed to list documents")
    }

    printer := output.NewPrinter(opts.Output)
    return printer.PrintList(docs)
}

3. Output Formatting Pattern

// pkg/output/printer.go
package output

import (
    "encoding/json"
    "io"
)

type Printer interface {
    Print(interface{}) error
    PrintList(interface{}) error
}

func NewPrinter(format string, writer io.Writer) Printer {
    switch format {
    case "json":
        return &JSONPrinter{writer: writer}
    case "yaml":
        return &YAMLPrinter{writer: writer}
    case "table", "wide":
        return &TablePrinter{writer: writer, wide: format == "wide"}
    default:
        return &TablePrinter{writer: writer}
    }
}

type JSONPrinter struct {
    writer io.Writer
}

func (p *JSONPrinter) Print(obj interface{}) error {
    encoder := json.NewEncoder(p.writer)
    encoder.SetIndent("", "  ")
    return encoder.Encode(obj)
}

4. Client Configuration Pattern

// pkg/client/client.go
package client

import (
    "github.com/go-resty/resty/v2"
    "github.com/yourorg/dtctl/pkg/config"
)

type Client struct {
    http    *resty.Client
    baseURL string
    token   string
}

func NewFromConfig(cfg *config.Config) (*Client, error) {
    ctx := cfg.CurrentContext()
    if ctx == nil {
        return nil, errors.New("no current context")
    }

    token := cfg.GetToken(ctx.TokenRef)
    if token == "" {
        return nil, errors.New("no token found")
    }

    httpClient := resty.New().
        SetBaseURL(ctx.Environment).
        SetAuthToken(token).
        SetRetryCount(3).
        AddRetryCondition(isRetryable).
        SetLogger(log.StandardLogger())

    return &Client{
        http:    httpClient,
        baseURL: ctx.Environment,
        token:   token,
    }, nil
}

func isRetryable(r *resty.Response, err error) bool {
    if err != nil {
        return true
    }

    // Retry on rate limit or server errors
    return r.StatusCode() == 429 || r.StatusCode() >= 500
}

Performance Considerations

1. Parallel Operations

Use goroutines for independent operations:

// Fetch multiple resources in parallel
var wg sync.WaitGroup
results := make(chan *Document, len(ids))
errors := make(chan error, len(ids))

for _, id := range ids {
    wg.Add(1)
    go func(id string) {
        defer wg.Done()
        doc, err := client.GetDocument(ctx, id)
        if err != nil {
            errors <- err
            return
        }
        results <- doc
    }(id)
}

wg.Wait()
close(results)
close(errors)

2. Caching

Implement caching for schemas and templates:

type Cache struct {
    schemas map[string]*Schema
    ttl     time.Duration
    mu      sync.RWMutex
}

func (c *Cache) GetSchema(id string) (*Schema, error) {
    c.mu.RLock()
    schema, ok := c.schemas[id]
    c.mu.RUnlock()

    if ok {
        return schema, nil
    }

    // Fetch and cache
    schema, err := fetchSchema(id)
    if err != nil {
        return nil, err
    }

    c.mu.Lock()
    c.schemas[id] = schema
    c.mu.Unlock()

    return schema, nil
}

3. Streaming

Stream large result sets:

func (h *Handler) StreamLogs(id string, follow bool) error {
    stream, err := h.client.StreamLogs(ctx, id)
    if err != nil {
        return err
    }
    defer stream.Close()

    scanner := bufio.NewScanner(stream)
    for scanner.Scan() {
        fmt.Println(scanner.Text())
    }
    return scanner.Err()
}

Security Considerations

1. Token Storage

  • Store tokens in config file with restricted permissions (0600)
  • Consider integration with OS keychain/credential manager
  • Support for credential helpers (similar to Docker)

2. TLS Configuration

httpClient.SetTLSClientConfig(&tls.Config{
    MinVersion: tls.VersionTLS12,
    // Add custom CA if needed
})

3. Input Validation

  • Validate all user inputs
  • Sanitize file paths
  • Validate resource IDs and names

Future Enhancements

Phase 2 Additions:

  1. Plugin System: Support for extending dtctl with plugins (using Go plugins or exec-based)
  2. Interactive Mode: TUI using bubbletea/lipgloss
  3. Local Development Mode: Mock server for testing
  4. Credential Providers: Integration with HashiCorp Vault, AWS Secrets Manager
  5. Advanced Caching: Persistent cache with TTL and invalidation
  6. Metrics: Built-in metrics collection for usage analytics
  7. Auto-update: Automatic version checking and updates

Summary

This architecture provides:

✅ Production-ready: Based on proven technologies (kubectl stack) ✅ Maintainable: Clear project structure and patterns ✅ Performant: Fast startup, efficient resource usage ✅ Cross-platform: Single binary for all major platforms ✅ Extensible: Easy to add new resources and commands ✅ Type-safe: Generated clients from OpenAPI specs ✅ Well-tested: Comprehensive testing strategy ✅ Professional: Modern CI/CD and release automation

The proposed stack minimizes external dependencies while leveraging battle-tested libraries from the Kubernetes ecosystem and Go community.