check

README

go-check

go-check is a library to help with development of monitoring plugins for tools like Icinga.

Usage

package main

import (
	"github.com/NETWAYS/go-check"
)

func main() {
	config := check.NewConfig()
	config.Name = "check_test"
	config.Readme = `Test Plugin`
	config.Version = "1.0.0"

	_ = config.FlagSet.StringP("hostname", "H", "localhost", "Hostname to check")

	config.ParseArguments()

	// Some checking should be done here, when --help is not passed

	check.Exitf(check.OK, "Everything is fine - answer=%d", 42)
}

OK - Everything is fine - answer=42
would exit with code 0

See the documentation on pkg.go.dev for more details and examples.

Plugins

A few plugins using go-check:

• check_cloud_aws
• check_cloud_azure
• check_cloud_gcp
• check_sentinelone
• check_sophos_central

License

Copyright (c) 2020 NETWAYS GmbH

This library is distributed under the GPL-2.0 or newer license found in the COPYING file.

Documentation

Index

• Constants
• Variables
• func BaseExit(rc int)
• func BoundaryToString(value float64) (s string)
• func CatchPanic()
• func DumpBenchmark()
• func DumpBenchmarkWhen(criteria bool)
• func Exit(rc int, output string, args ...interface{})
• func ExitError(err error)
• func ExitRaw(rc int, output ...string)
• func Exitf(rc int, output string, args ...interface{})
• func HandleTimeout(timeout int)
• func InitBenchmark(message string)
• func RecordBenchmark(message string)
• func StatusText(status int) string
• type Benchmark
  • func NewBenchmark(message string) (b *Benchmark)
  • func (b *Benchmark) Dump()
  • func (b *Benchmark) DumpWhen(criteria bool)
  • func (b *Benchmark) Record(message string)
• type BenchmarkEvent
• type Config
  • func NewConfig() *Config
  • func (c *Config) EnableTimeoutHandler()
  • func (c *Config) ParseArguments()
  • func (c *Config) ParseArray(arguments []string)
  • func (c *Config) SetupLogging()
• type Threshold
  • func ParseThreshold(spec string) (t *Threshold, err error)
  • func (t Threshold) DoesViolate(value float64) bool
  • func (t Threshold) String() (s string)

Examples

• CatchPanic
• Config
• Exit
• ExitError
• ExitRaw
• Exitf
• InitBenchmark
• NewBenchmark
• StatusText

Constants

const (
	// OK means everything is fine
	OK = 0
	// Warning means there is a problem the admin should review
	Warning = 1
	// Critical means there is a problem that requires immediate action
	Critical = 2
	// Unknown means the status can not be determined, probably due to an error or something missing
	Unknown = 3
)

Variables

var (
	PosInf = math.Inf(1)
	NegInf = math.Inf(-1)
)

var AllowExit = true

AllowExit lets you disable the call to os.Exit() in ExitXxx() functions of this package.

This should be used carefully and most likely only for testing.

var PrintStack = true

PrintStack prints the error stack when recovering from a panic with CatchPanic()

Functions

func BaseExit

func BaseExit(rc int)

func BoundaryToString

func BoundaryToString(value float64) (s string)

Convert a threshold bound to its string representation

func CatchPanic

func CatchPanic()

CatchPanic is a general function for defer, to capture any panic that occurred during runtime of a check

The function will recover from the condition and exit with a proper UNKNOWN status, while showing error and the call stack.

Example

defer CatchPanic()

panic("something bad happened")

Output:

UNKNOWN - Golang encountered a panic: something bad happened
would exit with code 3

func DumpBenchmark

func DumpBenchmark()

Dump the Benchmark to stdout

func DumpBenchmarkWhen

func DumpBenchmarkWhen(criteria bool)

Dump the Benchmark when criteria is met, to be used with defer and a boolean variable

func Exit

func Exit(rc int, output string, args ...interface{})

Exit prints the plugin output and exits the program

Deprecated, please use Exitf or ExitRaw.

Example

Exitf(OK, "Everything is fine - value=%d", 42)

Output:

OK - Everything is fine - value=42
would exit with code 0

func ExitError

func ExitError(err error)

ExitError exists with an Unknown state while reporting the error

Example

err := fmt.Errorf("connection to %s has been timed out", "localhost:12345")
ExitError(err)

Output:

UNKNOWN - connection to localhost:12345 has been timed out (*errors.errorString)
would exit with code 3

func ExitRaw

func ExitRaw(rc int, output ...string)

ExitRaw prints the plugin output with the state prefixed and exits the program.

Example:

OK - everything is fine

Example

ExitRaw(OK, "Everything is fine")

Output:

OK - Everything is fine
would exit with code 0

func Exitf

func Exitf(rc int, output string, args ...interface{})

Exitf prints the plugin output using formatting and exits the program.

Output is the formatting string, and the rest of the arguments help adding values.

Also see fmt package: https://golang.org/pkg/fmt

Example

Exitf(OK, "Everything is fine - value=%d", 42)

Output:

OK - Everything is fine - value=42
would exit with code 0

func HandleTimeout

func HandleTimeout(timeout int)

Helper for a goroutine, to wait for signals and timeout, and exit with a proper code

func InitBenchmark

func InitBenchmark(message string)

Initialize a Benchmark for the running program as static instance

Example

noinspection GoBoolExpressions

debug := true /* flags.Debug */
if debug {
	InitBenchmark("Start plugin")

	defer DumpBenchmarkWhen(debug /* flags.Debug */)
}

time.Sleep(1 * time.Second)
RecordBenchmark("Connecting to service")
time.Sleep(2 * time.Second)
RecordBenchmark("Connection open")

func RecordBenchmark

func RecordBenchmark(message string)

Recording timing and memory for the current program

func StatusText

func StatusText(status int) string

StatusText returns the string corresponding to a state

Example

fmt.Println(StatusText(OK), StatusText(Warning), StatusText(Critical), StatusText(Unknown))

Output:

OK WARNING CRITICAL UNKNOWN

Types

type Benchmark

type Benchmark struct {
	Events []*BenchmarkEvent
}

Benchmark records multiple events and provides functionality to dump the recorded events

var ActiveBenchmark *Benchmark

func NewBenchmark

func NewBenchmark(message string) (b *Benchmark)

NewBenchmark starts a new benchmark and records the message as event

Example

bench := NewBenchmark("Start plugin")
defer bench.DumpWhen(true /* flags.Debug */)

time.Sleep(1 * time.Second)
bench.Record("Connecting to service")
time.Sleep(2 * time.Second)
bench.Record("Connection open")

func (*Benchmark) Dump

func (b *Benchmark) Dump()

Dump the benchmark to stdout

func (*Benchmark) DumpWhen

func (b *Benchmark) DumpWhen(criteria bool)

Dump the benchmark when a criteria is met

Makes it simple to defer dumping by adding a boolean reference from a variable.

func (*Benchmark) Record

func (b *Benchmark) Record(message string)

Record the current step of execution

Use a short description, so that one knows at what stage the program is at. Time and offset will be calculated automatically.

type BenchmarkEvent

type BenchmarkEvent struct {
	Time       *time.Time
	Offset     *time.Duration
	Message    string
	TotalAlloc uint64
	HeapAlloc  uint64
}

BenchmarkEvent represents a single event during a benchmark with the time it occurred

type Config

type Config struct {
	Name          string
	Readme        string
	Version       string
	Timeout       int
	Verbose       bool
	Debug         bool
	PrintVersion  bool
	DefaultFlags  bool
	DefaultHelper bool
	FlagSet       *flag.FlagSet
}

Example

config := NewConfig()
config.Name = "check_test"
config.Readme = `Test Plugin`
config.Version = "1.0.0"

_ = config.FlagSet.StringP("hostname", "H", "localhost", "Hostname to check")

config.ParseArguments()

// Some checking should be done here

Exitf(OK, "Everything is fine - answer=%d", 42)

Output:

OK - Everything is fine - answer=42
would exit with code 0

func NewConfig

func NewConfig() *Config

func (*Config) EnableTimeoutHandler

func (c *Config) EnableTimeoutHandler()

Start the timeout and signal handler in a goroutine

func (*Config) ParseArguments

func (c *Config) ParseArguments()

func (*Config) ParseArray

func (c *Config) ParseArray(arguments []string)

func (*Config) SetupLogging

func (c *Config) SetupLogging()

type Threshold

type Threshold struct {
	Inside bool
	Lower  float64
	Upper  float64
}

Defining a threshold for any numeric value

Format: [@]start:end

Threshold Generate an alert if x... 10 < 0 or > 10, (outside the range of {0 .. 10}) 10: < 10, (outside {10 .. ∞}) ~:10 > 10, (outside the range of {-∞ .. 10}) 10:20 < 10 or > 20, (outside the range of {10 .. 20}) @10:20 ≥ 10 and ≤ 20, (inside the range of {10 .. 20})

Reference: https://www.monitoring-plugins.org/doc/guidelines.html#THRESHOLDFORMAT

func ParseThreshold

func ParseThreshold(spec string) (t *Threshold, err error)

Parse a Threshold from a string.

See Threshold for details.

func (Threshold) DoesViolate

func (t Threshold) DoesViolate(value float64) bool

Compares a value against the threshold, and returns true if the value violates the threshold.

func (Threshold) String

func (t Threshold) String() (s string)

String returns the plain representation of the Threshold