A minimal monitoring tool
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package main
import (
"errors"
"io/ioutil"
"time"
"git.iamthefij.com/iamthefij/slog"
"gopkg.in/yaml.v2"
)
var errInvalidConfig = errors.New("Invalid configuration")
// Config type is contains all provided user configuration
type Config struct {
CheckInterval SecondsOrDuration `yaml:"check_interval"`
Monitors []*Monitor
Alerts map[string]*Alert
}
// CommandOrShell type wraps a string or list of strings
// for executing a command directly or in a shell
type CommandOrShell struct {
ShellCommand string
Command []string
}
// Empty checks if the Command has a value
func (cos CommandOrShell) Empty() bool {
return (cos.ShellCommand == "" && cos.Command == nil)
}
// UnmarshalYAML allows unmarshalling either a string or slice of strings
// and parsing them as either a command or a shell command.
func (cos *CommandOrShell) UnmarshalYAML(unmarshal func(interface{}) error) error {
var cmd []string
err := unmarshal(&cmd)
// Error indicates this is shell command
if err != nil {
var shellCmd string
err := unmarshal(&shellCmd)
if err != nil {
return err
}
cos.ShellCommand = shellCmd
} else {
cos.Command = cmd
}
return nil
}
// SecondsOrDuration wraps a duration value for parsing a duration or seconds from YAML
// NOTE: This should be removed in favor of only parsing durations once compatibility is broken
type SecondsOrDuration struct {
value time.Duration
}
// Value returns a duration value
func (sod SecondsOrDuration) Value() time.Duration {
return sod.value
}
// UnmarshalYAML allows unmarshalling a duration value or seconds if an int was provided
func (sod *SecondsOrDuration) UnmarshalYAML(unmarshal func(interface{}) error) error {
var seconds int64
err := unmarshal(&seconds)
if err == nil {
sod.value = time.Second * time.Duration(seconds)
return nil
}
// Error indicates that we don't have an int
err = unmarshal(&sod.value)
return err
}
// IsValid checks config validity and returns true if valid
func (config Config) IsValid() (isValid bool) {
isValid = true
// Validate alerts
if config.Alerts == nil || len(config.Alerts) == 0 {
// This should never happen because there is a default alert named 'log' for now
slog.Errorf("Invalid alert configuration: Must provide at least one alert")
isValid = false
}
for _, alert := range config.Alerts {
if !alert.IsValid() {
slog.Errorf("Invalid alert configuration: %+v", alert.Name)
isValid = false
} else {
slog.Debugf("Loaded alert %s", alert.Name)
}
}
// Validate monitors
if config.Monitors == nil || len(config.Monitors) == 0 {
slog.Errorf("Invalid monitor configuration: Must provide at least one monitor")
isValid = false
}
for _, monitor := range config.Monitors {
if !monitor.IsValid() {
slog.Errorf("Invalid monitor configuration: %s", monitor.Name)
isValid = false
}
// Check that all Monitor alerts actually exist
for _, isUp := range []bool{true, false} {
for _, alertName := range monitor.GetAlertNames(isUp) {
if _, ok := config.Alerts[alertName]; !ok {
slog.Errorf(
"Invalid monitor configuration: %s. Unknown alert %s",
monitor.Name, alertName,
)
isValid = false
}
}
}
}
return isValid
}
// Init performs extra initialization on top of loading the config from file
func (config *Config) Init() (err error) {
for name, alert := range config.Alerts {
alert.Name = name
if err = alert.BuildTemplates(); err != nil {
return
}
}
return
}
// LoadConfig will read config from the given path and parse it
func LoadConfig(filePath string) (config Config, err error) {
data, err := ioutil.ReadFile(filePath)
if err != nil {
return
}
err = yaml.Unmarshal(data, &config)
if err != nil {
return
}
slog.Debugf("Config values:\n%v\n", config)
// Add log alert if not present
if PyCompat {
// Initialize alerts list if not present
if config.Alerts == nil {
config.Alerts = map[string]*Alert{}
}
if _, ok := config.Alerts["log"]; !ok {
config.Alerts["log"] = NewLogAlert()
}
}
// Finish initializing configuration
if err = config.Init(); err != nil {
return
}
if !config.IsValid() {
err = errInvalidConfig
return
}
return config, err
}