### Install go-metrics

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/rcrowley/go-metrics/README.md

Command to install the library via go get.

```sh
go get github.com/rcrowley/go-metrics
```

--------------------------------

### Install go-proxyproto

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/pires/go-proxyproto/README.md

Use 'go get' to install the go-proxyproto library. This command fetches and installs the latest version of the library.

```shell
$ go get -u github.com/pires/go-proxyproto
```

--------------------------------

### Install go-colorable

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/mattn/go-colorable/README.md

Use the go get command to add the package to your project.

```bash
$ go get github.com/mattn/go-colorable
```

--------------------------------

### Install color library

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/fatih/color/README.md

Command to install the package via go get.

```bash
go get github.com/fatih/color
```

--------------------------------

### Install doublestar

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/bmatcuk/doublestar/README.md

Use the go get command to install the package.

```bash
go get github.com/bmatcuk/doublestar
```

--------------------------------

### Install go-isatty

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/mattn/go-isatty/README.md

Command to install the library using the Go toolchain.

```bash
$ go get github.com/mattn/go-isatty
```

--------------------------------

### Install the YAML package

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/go.yaml.in/yaml/v3/README.md

Use the go get command to add the package to your Go project.

```bash
go get go.yaml.in/yaml/v3
```

--------------------------------

### Build and Install miekg/dns

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/acceptance_tests/dns-acceptance-release/src/test-recursor/vendor/github.com/miekg/dns/README.md

Instructions for building and installing the miekg/dns library using Go modules.

```bash
go get github.com/miekg/dns
go build github.com/miekg/dns
```

--------------------------------

### Install graphemes package

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/clipperhouse/uax29/v2/graphemes/README.md

Use `go get` to add the graphemes package to your project.

```bash
go get github.com/clipperhouse/uax29/v2/graphemes
```

--------------------------------

### Install Ginkgo Locally

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/onsi/ginkgo/v2/CONTRIBUTING.md

Installs Ginkgo locally using go install. Ensure you have Go installed and configured.

```bash
go install "./..."
```

--------------------------------

### Initialize and Start a SOCKS5 Server

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/cloudfoundry/go-socks5/README.md

Configures and starts a basic SOCKS5 proxy server on the local interface. Ensure the server is properly initialized before calling ListenAndServe.

```go
// Create a SOCKS5 server
conf := &socks5.Config{}
server, err := socks5.New(conf)
if err != nil {
  panic(err)
}

// Create SOCKS5 proxy on localhost port 8000
if err := server.ListenAndServe("tcp", "127.0.0.1:8000"); err != nil {
  panic(err)
}
```

--------------------------------

### Install Backoff Package

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/jpillora/backoff/README.md

Use 'go get' to install the backoff package. This command fetches and installs the package and its dependencies.

```bash
$ go get -v github.com/jpillora/backoff
```

--------------------------------

### Example output

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/go.yaml.in/yaml/v3/README.md

The expected output generated by the provided Go example code.

```text
--- t:
{Easy! {2 [3 4]}}

--- t dump:
a: Easy!
b:
  c: 2
  d: [3, 4]


--- m:
map[a:Easy! b:map[c:2 d:[3 4]]]

--- m dump:
a: Easy!
b:
  c: 2
  d:
  - 3
  - 4
```

--------------------------------

### Install StatHat support

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/rcrowley/go-metrics/README.md

Command to install the required StatHat Go client.

```sh
go get github.com/stathat/go
```

--------------------------------

### Serve Static Files

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/coredns/caddy/README.md

Start the Caddy server to serve files from the current working directory.

```bash
caddy
```

--------------------------------

### Install otgrpc package

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/grpc-ecosystem/grpc-opentracing/go/otgrpc/README.md

Command to install the OpenTracing gRPC middleware.

```bash
go get github.com/grpc-ecosystem/grpc-opentracing/go/otgrpc
```

--------------------------------

### Install Counterfeiter Tool Dependency

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/maxbrunsfeld/counterfeiter/v6/README.md

Add `counterfeiter` as a tool dependency using `go get -tool`. This is the first step before using `go generate` directives.

```shell
go get -tool github.com/maxbrunsfeld/counterfeiter/v6
```

--------------------------------

### Define a Ginkgo Test Suite

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/onsi/ginkgo/v2/README.md

A comprehensive example demonstrating Describe, Context, When, and It blocks to structure library checkout tests.

```go
import (
    . "github.com/onsi/ginkgo/v2"
    . "github.com/onsi/gomega"
    ...
)

var _ = Describe("Checking books out of the library", Label("library"), func() {
    var library *libraries.Library
    var book *books.Book
    var valjean *users.User
    BeforeEach(func() {
        library = libraries.NewClient()
        book = &books.Book{
            Title: "Les Miserables",
            Author: "Victor Hugo",
        }
        valjean = users.NewUser("Jean Valjean")
    })

    When("the library has the book in question", func() {
        BeforeEach(func(ctx SpecContext) {
            Expect(library.Store(ctx, book)).To(Succeed())
        })

        Context("and the book is available", func() {
            It("lends it to the reader", func(ctx SpecContext) {
                Expect(valjean.Checkout(ctx, library, "Les Miserables")).To(Succeed())
                Expect(valjean.Books()).To(ContainElement(book))
                Expect(library.UserWithBook(ctx, book)).To(Equal(valjean))
            }, SpecTimeout(time.Second * 5))
        })

        Context("but the book has already been checked out", func() {
            var javert *users.User
            BeforeEach(func(ctx SpecContext) {
                javert = users.NewUser("Javert")
                Expect(javert.Checkout(ctx, library, "Les Miserables")).To(Succeed())
            })

            It("tells the user", func(ctx SpecContext) {
                err := valjean.Checkout(ctx, library, "Les Miserables")
                Expect(err).To(MatchError("Les Miserables is currently checked out"))
            }, SpecTimeout(time.Second * 5))

            It("lets the user place a hold and get notified later", func(ctx SpecContext) {
                Expect(valjean.Hold(ctx, library, "Les Miserables")).To(Succeed())
                Expect(valjean.Holds(ctx)).To(ContainElement(book))

                By("when Javert returns the book")
                Expect(javert.Return(ctx, library, book)).To(Succeed())

                By("it eventually informs Valjean")
                notification := "Les Miserables is ready for pick up"
                Eventually(ctx, valjean.Notifications).Should(ContainElement(notification))

                Expect(valjean.Checkout(ctx, library, "Les Miserables")).To(Succeed())
                Expect(valjean.Books(ctx)).To(ContainElement(book))
                Expect(valjean.Holds(ctx)).To(BeEmpty())
            }, SpecTimeout(time.Second * 10))
        })  
    })

    When("the library does not have the book in question", func() {
        It("tells the reader the book is unavailable", func(ctx SpecContext) {
            err := valjean.Checkout(ctx, library, "Les Miserables")
            Expect(err).To(MatchError("Les Miserables is not in the library catalog"))
        }, SpecTimeout(time.Second * 5))
    })
})
```

--------------------------------

### Simple Backoff Example

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/jpillora/backoff/README.md

Demonstrates the basic usage of the backoff counter. It initializes a backoff with default settings, calls Duration() multiple times to observe increasing delays, and then resets it.

```go
b := &backoff.Backoff{
	//These are the defaults
	Min:    100 * time.Millisecond,
	Max:    10 * time.Second,
	Factor: 2,
	Jitter: false,
}

fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())

fmt.Printf("Reset!\n")
b.Reset()

fmt.Printf("%s\n", b.Duration())
```

```text
100ms
200ms
400ms
Reset!
100ms
```

--------------------------------

### Convert format-string logs to structured key-value logs

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/go-logr/logr/README.md

Examples demonstrating how to refactor standard format-string logging calls into structured logr-style calls.

```go
klog.V(4).Infof("Client is returning errors: code %v, error %v", responseCode, err)
```

```go
logger.Error(err, "client returned an error", "code", responseCode)
```

```go
klog.V(4).Infof("Got a Retry-After %ds response for attempt %d to %v", seconds, retries, url)
```

```go
logger.V(4).Info("got a retry-after response when requesting url", "attempt", retries, "after seconds", seconds, "url", url)
```

```go
log.Printf("unable to reflect over type %T")
```

```go
logger.Info("unable to reflect over type", "type", fmt.Sprintf("%T"))
```

--------------------------------

### Install Counterfeiter to `$GOPATH/bin`

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/maxbrunsfeld/counterfeiter/v6/README.md

Install `counterfeiter` globally to your `$GOPATH/bin` directory. This allows invoking the `counterfeiter` command directly from your shell, even outside of a Go module.

```shell
go install github.com/maxbrunsfeld/counterfeiter/v6
~/go/bin/counterfeiter

USAGE
	counterfeiter
		[-generate>] [-o <output-path>] [-p] [--fake-name <fake-name>]
		[-header <header-file>]
		[<source-path>] <interface> [-]
```

--------------------------------

### Create Root Span

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/opentracing/opentracing-go/README.md

Start a new trace without any parent or causal reference.

```go
    func xyz() {
        ...
        sp := opentracing.StartSpan("operation_name")
        defer sp.Finish()
        ...
    }
```

--------------------------------

### macOS Test Setup

Source: https://context7.com/cloudfoundry/bosh-dns-release/llms.txt

Configure loopback interfaces and network settings on macOS for running tests. This involves aliasing IP addresses to the loopback interface and adjusting the maximum number of connections.

```bash
sudo ifconfig lo0 alias 127.0.0.2 up
sudo ifconfig lo0 alias 127.0.0.3 up
sudo ifconfig lo0 alias 127.0.0.253 up
sudo ifconfig lo0 alias 127.0.0.254 up
sudo sysctl -w kern.ipc.somaxconn=1024
```

--------------------------------

### Full go-flags Example: Parsing Diverse Argument Types

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/jessevdk/go-flags/README.md

Demonstrates parsing various command-line arguments including slices, callbacks, required flags, choices, pointers, maps, and environment variables. Use flags.ParseArgs for testing with predefined arguments; use flags.Parse for actual command-line parsing.

```go
var opts struct {
	// Slice of bool will append 'true' each time the option
	// is encountered (can be set multiple times, like -vvv)
	Verbose []bool `short:"v" long:"verbose" description:"Show verbose debug information"`

	// Example of automatic marshalling to desired type (uint)
	Offset uint `long:"offset" description:"Offset"`

	// Example of a callback, called each time the option is found.
	Call func(string) `short:"c" description:"Call phone number"`

	// Example of a required flag
	Name string `short:"n" long:"name" description:"A name" required:"true"`

	// Example of a flag restricted to a pre-defined set of strings
	Animal string `long:"animal" choice:"cat" choice:"dog"`

	// Example of a value name
	File string `short:"f" long:"file" description:"A file" value-name:"FILE"`

	// Example of a pointer
	Ptr *int `short:"p" description:"A pointer to an integer"`

	// Example of a slice of strings
	StringSlice []string `short:"s" description:"A slice of strings"`

	// Example of a slice of pointers
	PtrSlice []*string `long:"ptrslice" description:"A slice of pointers to string"`

	// Example of a map
	IntMap map[string]int `long:"intmap" description:"A map from string to int"`

	// Example of env variable
	Thresholds  []int     `long:"thresholds" default:"1" default:"2" env:"THRESHOLD_VALUES"  env-delim:","`
}

// Callback which will invoke callto:<argument> to call a number.
// Note that this works just on OS X (and probably only with
// Skype) but it shows the idea.
opts.Call = func(num string) {
	cmd := exec.Command("open", "callto:"+num)
	cmd.Start()
	cmd.Process.Release()
}

// Make some fake arguments to parse.
args := []string{
	"-vv",
	"--offset=5",
	"-n", "Me",
	"--animal", "dog", // anything other than "cat" or "dog" will raise an error
	"-p", "3",
	"-s", "hello",
	"-s", "world",
	"--ptrslice", "hello",
	"--ptrslice", "world",
	"--intmap", "a:1",
	"--intmap", "b:5",
	"arg1",
	"arg2",
	"arg3",
}

// Parse flags from `args'. Note that here we use flags.ParseArgs for
// the sake of making a working example. Normally, you would simply use
// flags.Parse(&opts) which uses os.Args
args, err := flags.ParseArgs(&opts, args)

if err != nil {
	panic(err)
}

fmt.Printf("Verbosity: %v\n", opts.Verbose)
fmt.Printf("Offset: %d\n", opts.Offset)
fmt.Printf("Name: %s\n", opts.Name)
fmt.Printf("Animal: %s\n", opts.Animal)
fmt.Printf("Ptr: %d\n", *opts.Ptr)
fmt.Printf("StringSlice: %v\n", opts.StringSlice)
fmt.Printf("PtrSlice: [%v %v]\n", *opts.PtrSlice[0], *opts.PtrSlice[1])
fmt.Printf("IntMap: [a:%v b:%v]\n", opts.IntMap["a"], opts.IntMap["b"])
fmt.Printf("Remaining args: %s\n", strings.Join(args, " "))

// Output: Verbosity: [true true]
// Offset: 5
// Name: Me
// Ptr: 3
// StringSlice: [hello world]
// PtrSlice: [hello world]
// IntMap: [a:1 b:5]
// Remaining args: arg1 arg2 arg3

```

--------------------------------

### Define Command Line Options with Struct Tags

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/jessevdk/go-flags/README.md

Define command-line options using a struct and struct field tags. This example shows how to define a verbose flag that can be set multiple times.

```go
type Options struct {
	Verbose []bool `short:"v" long:"verbose" description:"Show verbose debug information"`
}
```

--------------------------------

### Configure Prometheus Metrics via Environment Variable

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/coredns/coredns/plugin/metrics/README.md

This example demonstrates using an environment variable to set the listening address for Prometheus metrics, offering dynamic configuration.

```corefile
. {
    prometheus localhost:{$PORT}
}
```

--------------------------------

### Log Information with logr.Logger in Go

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/go-logr/logr/README.md

Example of emitting log messages using the logr.Logger interface. This snippet shows logging an informational message with associated key-value pairs.

```go
func (app *appObject) Run() {
    app.logger.Info("starting up", "timestamp", time.Now())

    // ... app code ...
}
```

--------------------------------

### Backoff with Jitter for Randomization

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/jpillora/backoff/README.md

Shows how to enable 'Jitter' for randomized backoff durations. Seeding the random number generator is optional but allows for repeatable results. This example demonstrates the effect of jitter on consecutive calls and after a reset.

```go
import "math/rand"

b := &backoff.Backoff{
	Jitter: true,
}

rand.Seed(42)

fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())

fmt.Printf("Reset!\n")
b.Reset()

fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
```

```text
100ms
106.600049ms
281.228155ms
Reset!
100ms
104.381845ms
214.957989ms
```

--------------------------------

### Sample Encoded Queries with New Scheme

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/docs/encoding_queries.md

These examples demonstrate the new encoding scheme using a short dictionary. The default query includes status '0' (healthy), and additional parameters are appended.

```plaintext
a100a101n102s0
```

```plaintext
n102s0z103
```

--------------------------------

### Build Caddy with Plugins

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/coredns/caddy/README.md

Create a custom main.go file to include plugins when building Caddy from source.

```go
package main

import (
	"github.com/caddyserver/caddy/caddy/caddymain"

	// plug in plugins here, for example:
	// _ "import/path/here"
)

func main() {
	// optional: disable telemetry
	// caddymain.EnableTelemetry = false
	caddymain.Run()
}
```

--------------------------------

### Initialize blockdevice FS

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/prometheus/procfs/README.md

Initializes a blockdevice filesystem instance requiring access to both /proc and /sys.

```go
    fs, err := blockdevice.NewFS("/proc", "/sys")
    stats, err := fs.ProcDiskstats()
```

--------------------------------

### Implement simple backoff

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/jpillora/backoff/README.md

Demonstrates basic usage of the Backoff struct with default settings.

```go
b := &backoff.Backoff{
	//These are the defaults
	Min:    100 * time.Millisecond,
	Max:    10 * time.Second,
	Factor: 2,
	Jitter: false,
}

fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())

fmt.Printf("Reset!\n")
b.Reset()

fmt.Printf("%s\n", b.Duration())
```

--------------------------------

### Create and update metrics

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/rcrowley/go-metrics/README.md

Demonstrates initializing and updating various metric types including counters, gauges, histograms, meters, and timers.

```go
c := metrics.NewCounter()
metrics.Register("foo", c)
c.Inc(47)

g := metrics.NewGauge()
metrics.Register("bar", g)
g.Update(47)

r := NewRegistry()
g := metrics.NewRegisteredFunctionalGauge("cache-evictions", r, func() int64 { return cache.getEvictionsCount() })

s := metrics.NewExpDecaySample(1028, 0.015) // or metrics.NewUniformSample(1028)
h := metrics.NewHistogram(s)
metrics.Register("baz", h)
h.Update(47)

m := metrics.NewMeter()
metrics.Register("quux", m)
m.Mark(47)

t := metrics.NewTimer()
metrics.Register("bang", t)
t.Time(func() {})
t.Update(47)
```

--------------------------------

### Troubleshoot I/O Timeout Errors During 'go get'

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/google.golang.org/grpc/README.md

This console output shows a typical I/O timeout error when trying to 'go get' gRPC-Go, indicating a network issue with accessing google.golang.org.

```console
$ go get -u google.golang.org/grpc
package google.golang.org/grpc: unrecognized import path "google.golang.org/grpc" (https fetch: Get https://google.golang.org/grpc?go-get=1: dial tcp 216.239.37.1:443: i/o timeout)
```

--------------------------------

### Configure Separate Cache Sizes for Success and Denial

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/coredns/coredns/plugin/cache/README.md

Enables caching for 'example.org' with a positive cache size of 5000 entries and a negative cache size (for denials) of 2500 entries. This allows fine-grained control over cache capacity for different response types.

```corefile
example.org {
    cache {
        success 5000
        denial 2500
    }
}
```

--------------------------------

### Build All Files (Old System)

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/acceptance_tests/dns-acceptance-release/src/test-recursor/vendor/golang.org/x/sys/unix/README.md

Use this script to generate Go files for your current OS and architecture using the old build system. Ensure GOOS and GOARCH are set correctly. Requirements: bash, go.

```bash
mkall.sh
```

--------------------------------

### Define Interface for Mocking

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/maxbrunsfeld/counterfeiter/v6/README.md

Example interface definition used as the target for generating a test double.

```go
package foo

type MySpecialInterface interface {
		DoThings(string, uint64) (int, error)
}
```

--------------------------------

### Initialize QPACK Interop Files

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/quic-go/qpack/README.md

Use this command to initialize the QPACK interop files as a git submodule. This is a prerequisite for running the interop tests.

```bash
git submodule update --init --recursive
```

--------------------------------

### Show Build Commands (Old System)

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/acceptance_tests/dns-acceptance-release/src/test-recursor/vendor/golang.org/x/sys/unix/README.md

Run this command with the -n flag to see the build commands that will be executed by mkall.sh without actually running them. Requirements: bash, go.

```bash
mkall.sh -n
```

--------------------------------

### GET /instances - DNS API Endpoint

Source: https://context7.com/cloudfoundry/bosh-dns-release/llms.txt

Retrieves a list of all instances within the BOSH deployment. The response is newline-delimited JSON.

```APIDOC
## DNS API Endpoints

The BOSH DNS server exposes an API for querying instance information and health state. The API runs on a configurable port (default 53080) with mutual TLS authentication.

### GET /instances

*   **Method**: GET
*   **Endpoint**: `https://<ip_address>:<port>/instances`
*   **Description**: Retrieves all instances.
*   **Authentication**: Mutual TLS with `health.bosh-dns` common name.

### Request Example

```bash
# Get all instances
curl --cacert /var/vcap/jobs/bosh-dns/config/certs/api/server_ca.crt \
     --cert /var/vcap/jobs/bosh-dns/config/certs/api/client.crt \
     --key /var/vcap/jobs/bosh-dns/config/certs/api/client.key \
     https://127.0.0.1:53080/instances
```

### Response Example (Newline-delimited JSON)

```json
{"id":"abc123","group":"web-server","network":"default","deployment":"cf","ip":"10.0.0.5","domain":"bosh.","az":"z1","index":"0","health_state":"running"}
```
```

--------------------------------

### Preview Documentation Changes

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/onsi/ginkgo/v2/CONTRIBUTING.md

Builds and serves the documentation locally using Jekyll. Navigate to the docs directory and run this command to preview your documentation updates.

```bash
bundle && bundle exec jekyll serve
```

--------------------------------

### Initialize procfs and read CPU statistics

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/prometheus/procfs/README.md

Initializes the proc filesystem mount point and retrieves CPU statistics from /proc/stat.

```go
fs, err := procfs.NewFS("/proc")
stats, err := fs.Stat()
```

--------------------------------

### Example JSON Query for BOSH DNS

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/docs/encoding_queries.md

This JSON structure represents a sample query that needs to be encoded into a hostname. Consider its character count when evaluating encoding methods.

```json
{
  azs:[us-east-1,us-east-2],
  status:healthy,
  job:database
}
```

--------------------------------

### Benchmark Commands

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/cespare/xxhash/v2/README.md

Commands to compare pure-Go and assembly implementations using benchstat.

```bash
benchstat <(go test -tags purego -benchtime 500ms -count 15 -bench 'Sum64$')
benchstat <(go test -benchtime 500ms -count 15 -bench 'Sum64$')
```

--------------------------------

### Get All Instances via BOSH DNS API

Source: https://context7.com/cloudfoundry/bosh-dns-release/llms.txt

Use curl to query the BOSH DNS API for a list of all instances within the deployment. Requires mutual TLS authentication.

```bash
# Get all instances
curl --cacert /var/vcap/jobs/bosh-dns/config/certs/api/server_ca.crt \
     --cert /var/vcap/jobs/bosh-dns/config/certs/api/client.crt \
     --key /var/vcap/jobs/bosh-dns/config/certs/api/client.key \
     https://127.0.0.1:53080/instances

# Response (newline-delimited JSON):
# {"id":"abc123","group":"web-server","network":"default","deployment":"cf","ip":"10.0.0.5","domain":"bosh.","az":"z1","index":"0","health_state":"running"}
```

--------------------------------

### Read and scan /proc files

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/prometheus/procfs/CONTRIBUTING.md

Use util.ReadFileNoStat to read pseudo-files in one operation, then process with a bufio.Scanner.

```go
    data, err := util.ReadFileNoStat("/proc/cpuinfo")
    if err != nil {
        return err
    }
    reader := bytes.NewReader(data)
    scanner := bufio.NewScanner(reader)
```

--------------------------------

### Run QPACK Interop Tests

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/quic-go/qpack/README.md

Execute the interop tests for the QPACK implementation using the Go test command. Ensure interop files are initialized before running.

```bash
go test -v ./interop
```

--------------------------------

### View Interface File

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/maxbrunsfeld/counterfeiter/v6/README.md

Display the contents of the Go file containing the interface to be mocked.

```shell
$ cat path/to/foo/file.go
```

--------------------------------

### Client: Write PROXY Protocol Header

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/pires/go-proxyproto/README.md

Demonstrates how a client can write a PROXY protocol header before sending data. Ensure the target listener supports the PROXY protocol. The header can be constructed manually or using HeaderProxyFromAddrs if two connections are available.

```go
package main

import (
	io
	"log"
	"net"

	proxyproto "github.com/pires/go-proxyproto"
)

func chkErr(err error) {
	if err != nil {
		log.Fatalf("Error: %s", err.Error())
	}
}

func main() {
	// Dial some proxy listener e.g. https://github.com/mailgun/proxyproto
	target, err := net.ResolveTCPAddr("tcp", "127.0.0.1:2319")
	chkErr(err)

	conn, err := net.DialTCP("tcp", nil, target)
	chkErr(err)

	defer conn.Close()

	// Create a proxyprotocol header or use HeaderProxyFromAddrs() if you
	// have two conn's
	header := &proxyproto.Header{
		Version:            1,
		Command:            proxyproto.PROXY,
		TransportProtocol:  proxyproto.TCPv4,
		SourceAddr: &net.TCPAddr{
			IP:   net.ParseIP("10.1.1.1"),
			Port: 1000,
		},
		DestinationAddr: &net.TCPAddr{
			IP:   net.ParseIP("20.2.2.2"),
			Port: 2000,
		},
	}
	// After the connection was created write the proxy headers first
	_, err = header.WriteTo(conn)
	chkErr(err)
	// Then your data... e.g.:
	_, err = io.WriteString(conn, "HELO")
	chkErr(err)
}
```

--------------------------------

### Create Root Logger

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/go-logr/logr/README.md

Initialize the root logger with a chosen implementation and initial parameters. This is typically done early in an application's lifecycle.

```Go
func main() {
    // ... other setup code ...

    // Create the "root" logger.  We have chosen the "logimpl" implementation,
    // which takes some initial parameters and returns a logr.Logger.
    logger := logimpl.New(param1, param2)

    // ... other setup code ...
}
```

--------------------------------

### Plug into existing code

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/fatih/color/README.md

Apply global color settings to existing code blocks, ensuring they are unset afterwards.

```go
// Use handy standard colors
color.Set(color.FgYellow)

fmt.Println("Existing text will now be in yellow")
fmt.Printf("This one %s\n", "too")

color.Unset() // Don't forget to unset

// You can mix up parameters
color.Set(color.FgMagenta, color.Bold)
defer color.Unset() // Use it in your function

fmt.Println("All text will now be bold magenta.")
```

--------------------------------

### Create and Use EWMA Averages

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/VividCortex/ewma/README.md

Demonstrates creating both SimpleEWMA and VariableEWMA instances and adding samples to them. SimpleEWMA is created with no parameters, while VariableEWMA requires a decay parameter. Note the different resulting values.

```go
package main

import "github.com/VividCortex/ewma"

func main() {
	samples := [100]float64{
		4599, 5711, 4746, 4621, 5037, 4218, 4925, 4281, 5207, 5203, 5594, 5149,
	}

	e := ewma.NewMovingAverage()  //=> Returns a SimpleEWMA if called without params
	a := ewma.NewMovingAverage(5) //=> returns a VariableEWMA with a decay of 2 / (5 + 1)

	for _, f := range samples {
		e.Add(f)
		a.Add(f)
	}

	e.Value() //=> 13.577404704631077
	a.Value() //=> 1.5806140565521463e-12
}
```

--------------------------------

### Manage Go dependencies

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/prometheus/procfs/CONTRIBUTING.md

Commands to fetch specific versions of external packages.

```bash
# Pick the latest tagged release.
go get example.com/some/module/pkg

# Pick a specific version.
go get example.com/some/module/pkg@vX.Y.Z
```

--------------------------------

### Import doublestar

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/bmatcuk/doublestar/README.md

Include the package in your Go source files.

```go
import "github.com/bmatcuk/doublestar"
```

--------------------------------

### View Caddy CLI Help

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/coredns/caddy/README.md

Displays basic help information for the Caddy command-line interface. For more details, refer to the official CLI documentation.

```bash
caddy -h
```

--------------------------------

### Server: Accept PROXY Protocol Connections

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/pires/go-proxyproto/README.md

Wraps a standard net.Listener with a proxyproto.Listener to accept connections with PROXY protocol headers. The remote and local addresses of the connection will be populated from the header.

```go
package main

import (
	"log"
	"net"

	proxyproto "github.com/pires/go-proxyproto"
)

func main() {
	// Create a listener
	addr := "localhost:9876"
	list, err := net.Listen("tcp", addr)
	if err != nil {
		log.Fatalf("couldn't listen to %q: %q\n", addr, err.Error())
	}

	// Wrap listener in a proxyproto listener
	proxyListener := &proxyproto.Listener{Listener: list}
	defer proxyListener.Close()

	// Wait for a connection and accept it
	conn, err := proxyListener.Accept()
	defer conn.Close()

	// Print connection details
	if conn.LocalAddr() == nil {
		log.Fatal("couldn't retrieve local address")
	}
	log.Printf("local address: %q", conn.LocalAddr().String())

	if conn.RemoteAddr() == nil {
		log.Fatal("couldn't retrieve remote address")
	}
	log.Printf("remote address: %q", conn.RemoteAddr().String())
}
```

--------------------------------

### Check Version Against Constraints

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/Masterminds/semver/v3/README.md

Parses a constraint string and a version string, then evaluates if the version satisfies the constraint.

```go
c, err := semver.NewConstraint(">= 1.2.3")
if err != nil {
    // Handle constraint not being parsable.
}

v, err := semver.NewVersion("1.3")
if err != nil {
    // Handle version not being parsable.
}
// Check if the version meets the constraints. The variable a will be true.
a := c.Check(v)
```

--------------------------------

### Backoff with Net Package for Retries

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/jpillora/backoff/README.md

Illustrates using backoff with the 'net' package for handling network connection retries. It attempts to establish a TCP connection and, upon failure, waits for a backoff duration before retrying.

```go
b := &backoff.Backoff{
    Max:    5 * time.Minute,
}

for {
	conn, err := net.Dial("tcp", "example.com:5309")
	if err != nil {
		d := b.Duration()
		fmt.Printf("%s, reconnecting in %s", err, d)
		time.Sleep(d)
		continue
	}
	//connected
	b.Reset()
	conn.Write([]byte("hello world!"))
	// ... Read ... Write ... etc
	conn.Close()
	//disconnected
}
```

--------------------------------

### Use custom io.Writer

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/debug/vendor/github.com/fatih/color/README.md

Direct colorized output to a specific io.Writer.

```go
// Use your own io.Writer output
color.New(color.FgBlue).Fprintln(myWriter, "blue color!")

blue := color.New(color.FgBlue)
blue.Fprint(writer, "This will print text in blue.")
```

--------------------------------

### Unmarshal and Marshal YAML in Go

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/go.yaml.in/yaml/v2/README.md

Demonstrates how to unmarshal YAML data into a struct and a map, and then marshal them back into YAML format. Ensure struct fields are public for correct unmarshalling.

```Go
package main

import (
        "fmt"
        "log"

        "go.yaml.in/yaml/v2"
)

var data = `
a: Easy!
b:
  c: 2
  d: [3, 4]
`

// Note: struct fields must be public in order for unmarshal to
// correctly populate the data.
type T struct {
        A string
        B struct {
                RenamedC int   `yaml:"c"`
                D        []int `yaml:",flow"`
        }
}

func main() {
        t := T{}
    
        err := yaml.Unmarshal([]byte(data), &t)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- t:\n%v\n\n", t)
    
        d, err := yaml.Marshal(&t)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- t dump:\n%s\n\n", string(d))
    
        m := make(map[interface{}]interface{})
    
        err = yaml.Unmarshal([]byte(data), &m)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- m:\n%v\n\n", m)
    
        d, err = yaml.Marshal(&m)
        if err != nil {
                log.Fatalf("error: %v", err)
        }
        fmt.Printf("--- m dump:\n%s\n\n", string(d))
}

```

--------------------------------

### Instantiate Generated Fake

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/maxbrunsfeld/counterfeiter/v6/README.md

Import the generated package and instantiate the fake object for use in tests.

```go
import "my-repo/path/to/foo/foofakes"

var fake = &foofakes.FakeMySpecialInterface{}
```

--------------------------------

### Go Configuration Structures

Source: https://context7.com/cloudfoundry/bosh-dns-release/llms.txt

Defines the Go configuration structures for BOSH DNS. Useful for understanding the configuration schema and building tools that interact with BOSH DNS.

```go
package config

import (
    "time"
)

type Config struct {
    Address                  string       `json:"address"`
    Port                     int          `json:"port"`
    BindTimeout              DurationJSON `json:"timeout,omitempty"`
    RecursorMaxRetries       int          `json:"recursor_max_retries,omitempty"`
    RequestTimeout           DurationJSON `json:"request_timeout,omitempty"`
    RecursorTimeout          DurationJSON `json:"recursor_timeout,omitempty"`
    Recursors                []string     `json:"recursors,omitempty"`
    DisableRecursors         bool         `json:"disable_recursors,omitempty"`
    ConfigureSystemdResolved bool         `json:"configure_systemd_resolved,omitempty"`
    ExcludedRecursors        []string     `json:"excluded_recursors,omitempty"`
    RecordsFile              string       `json:"records_file,omitempty"`
    RecursorSelection        string       `json:"recursor_selection"` // "smart" or "serial"
    AliasFilesGlob           string       `json:"alias_files_glob,omitempty"`
    HandlersFilesGlob        string       `json:"handlers_files_glob,omitempty"`
    AddressesFilesGlob       string       `json:"addresses_files_glob,omitempty"`
    UpcheckDomains           []string     `json:"upcheck_domains,omitempty"`
    JobsDir                  string       `json:"jobs_dir,omitempty"`
    LogLevel                 string       `json:"log_level,omitempty"`
    API                      APIConfig    `json:"api"`
    Health                   HealthConfig `json:"health"`
    Metrics                  MetricsConfig `json:"metrics"`
    Cache                    Cache        `json:"cache"`
    InternalUpcheckDomain    InternalUpcheckDomain `json:"internal_upcheck_domain"`
    Logging                  LoggingConfig `json:"logging,omitempty"`
}

type APIConfig struct {
    Port            int    `json:"port"`
    CertificateFile string `json:"certificate_file"`
    PrivateKeyFile  string `json:"private_key_file"`
    CAFile          string `json:"ca_file"`
}

type HealthConfig struct {
    Enabled                 bool         `json:"enabled"`
    Port                    int          `json:"port"`
    CertificateFile         string       `json:"certificate_file"`
    PrivateKeyFile          string       `json:"private_key_file"`
    CAFile                  string       `json:"ca_file"`
    CheckInterval           DurationJSON `json:"check_interval,omitempty"`
    MaxTrackedQueries       int          `json:"max_tracked_queries,omitempty"`
    SynchronousCheckTimeout DurationJSON `json:"synchronous_check_timeout,omitempty"`
}

type MetricsConfig struct {
    Enabled bool   `json:"enabled"`
    Address string `json:"address"`
    Port    int    `json:"port"`
}

```

```go
// Example: Load configuration from file
func LoadConfig(path string) (*Config, error) {
    cfg, err := LoadFromFile(path)
    if err != nil {
        return nil, err
    }
    return &cfg, nil
}

```

```go
// Example: Create default configuration
func DefaultConfig() Config {
    return NewDefaultConfig()
}

```

--------------------------------

### Define OS interface

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/bmatcuk/doublestar/README.md

Interface for abstracting filesystem operations, allowing custom implementations or cross-platform testing.

```go
type OS interface {
    Lstat(name string) (os.FileInfo, error)
    Open(name string) (*os.File, error)
    PathSeparator() rune
    Stat(name string) (os.FileInfo, error)
}
```

--------------------------------

### Run project tests

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/prometheus/procfs/CONTRIBUTING.md

Execute the test suite to ensure changes are valid before committing.

```makefile
make test         # Make sure all the tests pass before you commit and push :)
```

--------------------------------

### Update Go modules and vendor directory

Source: https://github.com/cloudfoundry/bosh-dns-release/blob/master/src/bosh-dns/vendor/github.com/prometheus/procfs/CONTRIBUTING.md

Commands to clean up module files and synchronize the vendor directory.

```bash
# The GO111MODULE variable can be omitted when the code isn't located in GOPATH.
GO111MODULE=on go mod tidy

GO111MODULE=on go mod vendor
```