Switch config to yaml

config/alarm.go

@@ -0,0 +1,14 @@
+package config
+
+type Alarm struct {
+	Name  string                 `yaml:"name"`
+	Type  string                 `yaml:"type"`
+	Attrs map[string]interface{} `yaml:",inline"`
+}
+
+func (alm Alarm) NameOrType() string {
+	if alm.Name == "" {
+		return alm.Type
+	}
+	return alm.Name
+}

config/check.go

@@ -0,0 +1,14 @@
+package config
+
+type Check struct {
+	Name  string                 `yaml:"name"`
+	Type  string                 `yaml:"type"`
+	Attrs map[string]interface{} `yaml:",inline"`
+}
+
+func (chk Check) NameOrType() string {
+	if chk.Name == "" {
+		return chk.Type
+	}
+	return chk.Name
+}

config/config.go

@@ -1,89 +1,52 @@
 package config
 
 import (
-	"fmt"
+	yaml "gopkg.in/yaml.v2"
-	"git.binarythought.com/cdramey/alrm/alarm"
+	"io"
 	"os"
 	"time"
 )
 
 type Config struct {
-	Groups     map[string]*Group
+	Interval   time.Duration     `yaml:"interval"`
-	Alarms     map[string]alarm.Alarm
+	Listen     string            `yaml:"listen"`
-	Interval   time.Duration
+	DebugLevel int               `yaml:"debug_level"`
-	DebugLevel int
+	APIKey     string            `yaml:"api_key"`
-	Listen     string
+	APIKeyFile string            `yaml:"api_key_file"`
-	Path       string
+	WebRoot    string            `yaml:"web_root"`
-	APIKey     []byte
+	Hosts      []Host            `yaml:"hosts"`
-	APIKeyFile string
+	Alarms     []Alarm           `yaml:"alarms"`
+	Groups     map[string][]Host `yaml:"groups"`
 }
 
-func (c *Config) NewAlarm(name string, typename string) (alarm.Alarm, error) {
+func New() *Config {
-	if c.Alarms == nil {
+	return &Config{
-		c.Alarms = make(map[string]alarm.Alarm)
+		Interval:   30 * time.Second,
+		Listen:     "127.0.0.1:8282",
+		DebugLevel: 0,
+		WebRoot:    "/",
 	}
-
-	if _, exists := c.Alarms[name]; exists {
-		return nil, fmt.Errorf("alarm %s already exists", name)
-	}
-
-	a, err := alarm.NewAlarm(name, typename)
-	if err != nil {
-		return nil, err
-	}
-	c.Alarms[name] = a
-
-	return a, nil
-}
-
-func (c *Config) NewGroup(name string) (*Group, error) {
-	if c.Groups == nil {
-		c.Groups = make(map[string]*Group)
-	}
-
-	if _, exists := c.Groups[name]; exists {
-		return nil, fmt.Errorf("group %s already exists", name)
-	}
-
-	group := &Group{Name: name}
-	c.Groups[name] = group
-	return group, nil
-}
-
-func (c *Config) SetInterval(val string) error {
-	interval, err := time.ParseDuration(val)
-	if err != nil {
-		return err
-	}
-
-	c.Interval = interval
-	return nil
 }
 
 func ReadConfig(fn string, debuglvl int) (*Config, error) {
-	cfg := &Config{
+	f, err := os.Open(fn)
-		// Default check interval, 30 seconds
-		Interval: time.Second * 30,
-		// Default listen address
-		Listen:     "127.0.0.1:8282",
-		DebugLevel: debuglvl,
-		Path:       fn,
-		// API keyfile defaults to alrmrc.key
-		APIKeyFile: fn + ".key",
-	}
-
-	pr := &parser{config: cfg}
-	if err := pr.parse(); err != nil {
-		return nil, err
-	}
-
-	if len(cfg.APIKey) == 0 {
-		b, err := os.ReadFile(cfg.APIKeyFile)
 	if err != nil {
 		return nil, err
 	}
-		cfg.APIKey = b
+
+	h, err := io.ReadAll(f)
+	if err != nil {
+		return nil, err
 	}
 
+	cfg := New()
+	err = yaml.UnmarshalStrict(h, &cfg)
+	if err != nil {
+		return nil, err
+	}
+	err = cfg.Validate()
+	if err != nil {
+		return nil, err
+	}
 	return cfg, nil
 }

config/config_test.go

@@ -0,0 +1,57 @@
+package config
+
+import (
+	"strings"
+	"testing"
+)
+
+// Is the absence of hosts and groups detected?
+func TestNoHosts(t *testing.T) {
+	_, err := ReadConfig("testdata/no_hosts.yaml", 0)
+	if err != ERR_NO_GROUPHOST {
+		t.Errorf("missing hosts/groups not detected: %s", err.Error())
+	}
+}
+
+// Are duplicate host names detected?
+func TestDupHosts(t *testing.T) {
+	_, err := ReadConfig("testdata/dup_hosts.yaml", 0)
+	if err == nil || !strings.HasPrefix(err.Error(), "duplicate host") {
+		t.Errorf("duplicate hosts not detected: %s", err.Error())
+	}
+}
+
+// Are duplicate host names inside groups detected?
+func TestDupGroupHosts(t *testing.T) {
+	_, err := ReadConfig("testdata/dup_group_hosts.yaml", 0)
+	if err == nil || !strings.HasPrefix(err.Error(), "duplicate host") {
+		t.Errorf("duplicate hosts not detected: %s", err.Error())
+	}
+}
+
+// Test if api_key and api_key_file are both defined
+func TestDupAPI(t *testing.T) {
+	_, err := ReadConfig("testdata/dup_api_key.yaml", 0)
+	if err != ERR_DUP_API {
+		t.Errorf("missing api key/api key file not detected: %s", err.Error())
+	}
+}
+
+// Are undefined api key / key files detected?
+func TestUndefinedAPI(t *testing.T) {
+	_, err := ReadConfig("testdata/no_api_key.yaml", 0)
+	if err != ERR_NO_API {
+		t.Errorf("undefined api key/api key file not detected: %s", err.Error())
+	}
+}
+
+// Are missing api key files detected?
+func TestMissingAPIKey(t *testing.T) {
+	_, err := ReadConfig("testdata/missing_api_keyfile.yaml", 0)
+	if err != ERR_MISSING_KEYFILE {
+		t.Errorf("missing api key file not detected: %s", err.Error())
+	}
+}
+
+// Test if referenced alarm exists (and is a valid type)
+// Test if referenced check exists (and is a valid type)

config/group.go

@@ -1,36 +0,0 @@
-package config
-
-import (
-	"fmt"
-)
-
-type Group struct {
-	Name  string
-	Hosts map[string]*Host
-}
-
-func (ag *Group) NewHost(name string) (*Host, error) {
-	if ag.Hosts == nil {
-		ag.Hosts = make(map[string]*Host)
-	}
-
-	if _, exists := ag.Hosts[name]; exists {
-		return nil, fmt.Errorf("host %s already exists", name)
-	}
-
-	host := &Host{Name: name}
-	ag.Hosts[name] = host
-	return host, nil
-}
-
-func (ag *Group) Check(debuglvl int) error {
-	for _, host := range ag.Hosts {
-		for _, chk := range host.Checks {
-			err := chk.Check(debuglvl)
-			if err != nil {
-				return err
-			}
-		}
-	}
-	return nil
-}

config/host.go

@@ -1,27 +1,14 @@
 package config
 
-import (
-	"git.binarythought.com/cdramey/alrm/check"
-)
-
 type Host struct {
-	Name    string
+	Name    string  `yaml:"name"`
-	Address string
+	Address string  `yaml:"address"`
-	Checks  []check.Check
+	Checks  []Check `yaml:"checks"`
 }
 
-func (ah *Host) GetAddress() string {
+func (hst *Host) NameOrAddress() string {
-	if ah.Address != "" {
+	if hst.Name == "" {
-		return ah.Address
+		return hst.Address
 	}
-	return ah.Name
+	return hst.Name
-}
-
-func (ah *Host) NewCheck(name string) (check.Check, error) {
-	chk, err := check.NewCheck(name, ah.GetAddress())
-	if err != nil {
-		return nil, err
-	}
-	ah.Checks = append(ah.Checks, chk)
-	return chk, nil
 }

config/parser.go

@@ -1,264 +0,0 @@
-package config
-
-import (
-	"fmt"
-	"git.binarythought.com/cdramey/alrm/alarm"
-	"git.binarythought.com/cdramey/alrm/check"
-	"strings"
-)
-
-const (
-	PR_NONE = iota
-	PR_SET
-	PR_MONITOR
-	PR_GROUP
-	PR_HOST
-	PR_CHECK
-	PR_ALARM
-)
-
-type parser struct {
-	config        *Config
-	states        []int
-	lastHost      *Host
-	lastGroup     *Group
-	lastCheck     check.Check
-	lastAlarm     alarm.Alarm
-	lastAlarmName string
-}
-
-func (p *parser) parse() error {
-	tok, err := NewTokenizer(p.config.Path)
-	if err != nil {
-		return err
-	}
-	defer tok.Close()
-
-	for tok.Scan() {
-		tk := tok.Text()
-	stateswitch:
-		switch p.state() {
-		case PR_NONE:
-			switch strings.ToLower(tk) {
-			case "monitor":
-				p.setState(PR_MONITOR)
-			case "set":
-				p.setState(PR_SET)
-			case "alarm":
-				p.setState(PR_ALARM)
-			default:
-				return fmt.Errorf("invalid token in %s, line %d: \"%s\"",
-					p.config.Path, tok.Line(), tk)
-			}
-
-		case PR_SET:
-			key := strings.ToLower(tk)
-			if !tok.Scan() {
-				return fmt.Errorf("empty value name for set in %s, line %d",
-					p.config.Path, tok.Line())
-			}
-
-			value := tok.Text()
-			switch key {
-			case "interval":
-				err := p.config.SetInterval(value)
-				if err != nil {
-					return fmt.Errorf(
-						"invalid duration for interval in %s, line %d: \"%s\"",
-						p.config.Path, tok.Line(), value,
-					)
-				}
-			case "listen":
-				p.config.Listen = value
-			case "api.key":
-				p.config.APIKey = []byte(value)
-			case "api.keyfile":
-				p.config.APIKeyFile = value
-			default:
-				return fmt.Errorf("unknown key for set in %s, line %d: \"%s\"",
-					p.config.Path, tok.Line(), tk,
-				)
-			}
-			p.prevState()
-
-		case PR_MONITOR:
-			switch strings.ToLower(tk) {
-			case "host":
-				p.setState(PR_HOST)
-
-			case "group":
-				p.setState(PR_GROUP)
-
-			default:
-				p.prevState()
-				goto stateswitch
-			}
-
-		case PR_GROUP:
-			if p.lastGroup == nil {
-				p.lastGroup, err = p.config.NewGroup(tk)
-				if err != nil {
-					return fmt.Errorf("%s in %s, line %d",
-						err.Error(), p.config.Path, tok.Line(),
-					)
-				}
-				continue
-			}
-
-			switch strings.ToLower(tk) {
-			case "host":
-				p.setState(PR_HOST)
-
-			default:
-				p.prevState()
-				goto stateswitch
-			}
-
-		case PR_HOST:
-			// If a host has no group, inherit the host name
-			if p.lastGroup == nil {
-				p.lastGroup, err = p.config.NewGroup(tk)
-				if err != nil {
-					return fmt.Errorf("%s in %s, line %d",
-						err.Error(), p.config.Path, tok.Line(),
-					)
-				}
-			}
-
-			if p.lastHost == nil {
-				p.lastHost, err = p.lastGroup.NewHost(tk)
-				if err != nil {
-					return fmt.Errorf("%s in %s, line %d",
-						err.Error(), p.config.Path, tok.Line(),
-					)
-				}
-				continue
-			}
-
-			switch strings.ToLower(tk) {
-			case "address":
-				if !tok.Scan() {
-					return fmt.Errorf("empty address for host in %s, line %d",
-						p.config.Path, tok.Line())
-				}
-				p.lastHost.Address = tok.Text()
-
-			case "check":
-				p.setState(PR_CHECK)
-
-			default:
-				p.prevState()
-				goto stateswitch
-			}
-
-		case PR_CHECK:
-			if p.lastCheck == nil {
-				p.lastCheck, err = p.lastHost.NewCheck(tk)
-				if err != nil {
-					return fmt.Errorf("%s in %s, line %d",
-						err.Error(), p.config.Path, tok.Line())
-				}
-				continue
-			}
-			cont, err := p.lastCheck.Parse(tk)
-			if err != nil {
-				return fmt.Errorf("%s in %s, line %d",
-					err.Error(), p.config.Path, tok.Line())
-			}
-			if !cont {
-				p.lastCheck = nil
-				p.prevState()
-				goto stateswitch
-			}
-
-		case PR_ALARM:
-			if p.lastAlarm == nil {
-				if p.lastAlarmName == "" {
-					p.lastAlarmName = tk
-					continue
-				}
-
-				p.lastAlarm, err = p.config.NewAlarm(p.lastAlarmName, tk)
-				if err != nil {
-					return fmt.Errorf("%s in %s, line %d",
-						err.Error(), p.config.Path, tok.Line())
-				}
-				p.lastAlarmName = ""
-				continue
-			}
-			cont, err := p.lastAlarm.Parse(tk)
-			if err != nil {
-				return fmt.Errorf("%s in %s, line %d",
-					err.Error(), p.config.Path, tok.Line())
-			}
-			if !cont {
-				p.lastAlarm = nil
-				p.prevState()
-				goto stateswitch
-			}
-
-		default:
-			return fmt.Errorf("unknown parser state: %d", p.state())
-		}
-	}
-	if err := tok.Err(); err != nil {
-		return err
-	}
-	return nil
-}
-
-func (p *parser) state() int {
-	if len(p.states) < 1 {
-		return PR_NONE
-	}
-	return p.states[len(p.states)-1]
-}
-
-func (p *parser) setState(state int) {
-	switch state {
-	case PR_SET, PR_MONITOR:
-		fallthrough
-	case PR_GROUP:
-		p.lastGroup = nil
-		fallthrough
-	case PR_HOST:
-		p.lastHost = nil
-		p.lastCheck = nil
-	}
-
-	if p.config.DebugLevel > 1 {
-		fmt.Printf("Parser state: %s", p.stateName())
-	}
-	p.states = append(p.states, state)
-	if p.config.DebugLevel > 1 {
-		fmt.Printf(" -> %s\n", p.stateName())
-	}
-}
-
-func (p *parser) prevState() int {
-	if len(p.states) > 0 {
-		p.states = p.states[:len(p.states)-1]
-	}
-	return p.state()
-}
-
-func (p *parser) stateName() string {
-	switch p.state() {
-	case PR_NONE:
-		return "PR_NONE"
-	case PR_SET:
-		return "PR_SET"
-	case PR_MONITOR:
-		return "PR_MONITOR"
-	case PR_GROUP:
-		return "PR_GROUP"
-	case PR_HOST:
-		return "PR_HOST"
-	case PR_CHECK:
-		return "PR_CHECK"
-	case PR_ALARM:
-		return "PR_ALARM"
-	default:
-		return "UNKNOWN"
-	}
-}

config/testdata/comments-inline.tok

@@ -1,5 +0,0 @@
-one #one
-"two#three"
-# "three"
-four
-# EOF

config/testdata/comments.tok

@@ -1,6 +0,0 @@
-# one
-one
-#two
-two
-   # three
-   three

config/testdata/dup_api_key.yaml

@@ -0,0 +1,9 @@
+interval: 30s
+api_key: bogus
+api_key_file: bogus.key
+
+hosts:
+  - name: localhost
+    address: 127.0.0.1
+    checks:
+      - type: ping

config/testdata/dup_group_hosts.yaml

@@ -0,0 +1,13 @@
+interval: 30s
+api_key: bogus
+
+groups:
+  servers:
+    - name: localhost
+      address: 127.0.0.1
+      checks:
+        - type: ping
+    - name: localhost
+      address: 127.0.0.1
+      checks:
+        - type: ping

config/testdata/dup_hosts.yaml

@@ -0,0 +1,12 @@
+interval: 30s
+api_key: bogus
+
+hosts:
+  - name: localhost
+    address: 127.0.0.1
+    checks:
+      - type: ping
+  - name: localhost
+    address: 127.0.0.1
+    checks:
+      - type: ping

config/testdata/missing_api_keyfile.yaml

@@ -0,0 +1,8 @@
+interval: 30s
+api_key_file: testdata/bogus.key
+
+hosts:
+  - name: localhost
+    address: 127.0.0.1
+    checks:
+      - type: ping

config/testdata/no_api_key.yaml

@@ -0,0 +1,7 @@
+interval: 30s
+
+hosts:
+  - name: localhost
+    address: 127.0.0.1
+    checks:
+      - type: ping

config/testdata/no_hosts.yaml

@@ -0,0 +1,2 @@
+interval: 30s
+api_key: bogus

config/testdata/quotes-empty.tok

@@ -1,3 +0,0 @@
-one "" three
-"" five ""
-seven

config/testdata/quotes-multiline.tok

@@ -1,6 +0,0 @@
-"one
-two"   'three
-four'
-
-`five
-  six`

config/testdata/quotes.tok

@@ -1,3 +0,0 @@
-"one" 'two' `three`
-
-`four` 'five' "six"

config/testdata/simple-multiline.tok

@@ -1,6 +0,0 @@
-one two three
-four five
-
-
-six
-

config/testdata/simple-spaces.tok

@@ -1 +0,0 @@
-one two three    four five six

config/tokenizer.go

@@ -1,157 +0,0 @@
-package config
-
-import (
-	"bufio"
-	"fmt"
-	"io"
-	"os"
-	"strings"
-	"unicode"
-)
-
-const (
-	TK_NONE = iota
-	TK_VAL
-	TK_QUOTE
-	TK_COMMENT
-)
-
-type Tokenizer struct {
-	curline int
-	repline int
-	file    *os.File
-	reader  *bufio.Reader
-	text    string
-	err     error
-}
-
-func NewTokenizer(fn string) (*Tokenizer, error) {
-	var err error
-	tk := &Tokenizer{curline: 1}
-	tk.file, err = os.Open(fn)
-	if err != nil {
-		return nil, err
-	}
-
-	tk.reader = bufio.NewReader(tk.file)
-	return tk, nil
-}
-
-func (t *Tokenizer) Close() error {
-	return t.file.Close()
-}
-
-func (t *Tokenizer) Scan() bool {
-	t.repline = t.curline
-	state := TK_NONE
-	t.text = ""
-
-	var b strings.Builder
-	var quo rune
-	for {
-		var r rune
-		r, _, t.err = t.reader.ReadRune()
-		if t.err != nil {
-			break
-		}
-		if r == unicode.ReplacementChar {
-			t.err = fmt.Errorf("invalid utf-8 encoding on line %s", t.repline)
-			break
-		}
-
-		switch state {
-		case TK_NONE:
-			// When between values, increment both the reported line
-			// and the current line, since there's not yet anything
-			// to report
-			if r == '\n' {
-				t.repline++
-				t.curline++
-			}
-
-			// If we're between values and we encounter a space
-			// or a control character, ignore it
-			if unicode.IsSpace(r) || unicode.IsControl(r) {
-				continue
-			}
-
-			// If we're between values and we encounter a #, it's
-			// the beginning of a comment
-			if r == '#' {
-				state = TK_COMMENT
-				continue
-			}
-
-			// If we're between values and we get a quote character
-			// treat it as the beginning of a string literal
-			if r == '"' || r == '\'' || r == '`' {
-				state = TK_QUOTE
-				quo = r
-				continue
-			}
-
-			b.WriteRune(r)
-			state = TK_VAL
-
-		case TK_VAL:
-			// In values, only increment the current line, so
-			// if an error is reported, it reports the line
-			// the value starts on
-			if r == '\n' {
-				t.curline++
-			}
-
-			// If we're in a normal value and we encounter a space
-			// or a control character, end value
-			if unicode.IsSpace(r) || unicode.IsControl(r) {
-				goto end
-			}
-			b.WriteRune(r)
-
-		case TK_QUOTE:
-			// In quotes, only increment the current line, so
-			// if an error is reported, it reports the line
-			// the quoted value starts on
-			if r == '\n' {
-				t.curline++
-			}
-
-			// End this quote if it's another quote of the same rune
-			if r == quo {
-				goto end
-			}
-			b.WriteRune(r)
-
-		case TK_COMMENT:
-			// Comments are ignored, until a new line is encounter
-			// at which point, increment the current and reported line
-			if r == '\n' {
-				t.curline++
-				t.repline++
-				state = TK_NONE
-			}
-			continue
-		}
-	}
-
-end:
-	if t.err == nil || t.err == io.EOF {
-		t.text = b.String()
-	}
-	return t.err == nil
-}
-
-func (t *Tokenizer) Text() string {
-	return t.text
-}
-
-func (t *Tokenizer) Line() int {
-	return t.repline
-}
-
-func (t *Tokenizer) Err() error {
-	if t.err == io.EOF {
-		return nil
-	}
-	return t.err
-}

config/tokenizer_test.go

@@ -1,83 +0,0 @@
-package config
-
-import (
-	"encoding/json"
-	"testing"
-)
-
-func TestSimpleSpaces(t *testing.T) {
-	runTest(t, "simple-spaces",
-		`[["one","two","three","four","five","six"]]`,
-	)
-}
-
-func TestSimpleMultiline(t *testing.T) {
-	runTest(t, "simple-multiline",
-		`[["one","two","three"],["four","five"],[],[],["six"]]`,
-	)
-}
-
-func TestQuotes(t *testing.T) {
-	runTest(t, "quotes",
-		`[["one","two","three"],[],["four","five","six"]]`,
-	)
-}
-
-func TestQuotesMultiline(t *testing.T) {
-	runTest(t, "quotes-multiline",
-		`[["one\ntwo"],["three\nfour"],[],[],["five\n  six"]]`,
-	)
-}
-
-func TestQuotesEmpty(t *testing.T) {
-	runTest(t, "quotes-empty",
-		`[["one","","three"],["","five",""],["seven"]]`,
-	)
-}
-
-func TestComments(t *testing.T) {
-	runTest(t, "comments",
-		`[[],["one"],[],["two"],[],["three"]]`,
-	)
-}
-
-func TestCommentsInline(t *testing.T) {
-	runTest(t, "comments-inline",
-		`[["one"],["two#three"],[],["four"]]`,
-	)
-}
-
-func runTest(t *testing.T, bn string, exp string) {
-	t.Logf("Running testdata/%s.tok.. ", bn)
-	tok, err := NewTokenizer("testdata/" + bn + ".tok")
-	if err != nil {
-		t.Fatalf("%s", err.Error())
-	}
-	defer tok.Close()
-
-	tokens := [][]string{}
-	for tok.Scan() {
-		ln := tok.Line()
-		tl := len(tokens)
-		if tl < ln {
-			for i := tl; i < ln; i++ {
-				tokens = append(tokens, []string{})
-			}
-		}
-		tokens[ln-1] = append(tokens[ln-1], tok.Text())
-	}
-	if tok.Err() != nil {
-		t.Fatalf("%s", tok.Err())
-	}
-
-	out, err := json.Marshal(tokens)
-	if err != nil {
-		t.Fatalf("%s", err)
-	}
-
-	if exp != string(out) {
-		t.Logf("Expected: %s", exp)
-		t.Logf("Got:      %s", out)
-		t.FailNow()
-	}
-}

config/validate.go

@@ -0,0 +1,63 @@
+package config
+
+import (
+	"fmt"
+	"os"
+)
+
+var ERR_DUP_API error = fmt.Errorf(
+	"api key and api key file cannot both be defined",
+)
+var ERR_NO_API error = fmt.Errorf(
+	"no api key or api key file defined",
+)
+var ERR_NO_GROUPHOST error = fmt.Errorf(
+	"no groups or hosts configured",
+)
+var ERR_MISSING_KEYFILE error = fmt.Errorf(
+	"api key file not found",
+)
+
+func (cfg *Config) Validate() error {
+	if cfg.APIKey != "" && cfg.APIKeyFile != "" {
+		return ERR_DUP_API
+	}
+
+	if cfg.APIKey == "" && cfg.APIKeyFile == "" {
+		return ERR_NO_API
+	}
+
+	if cfg.APIKeyFile != "" {
+		if _, err := os.Stat(cfg.APIKeyFile); err != nil {
+			return ERR_MISSING_KEYFILE
+		}
+	}
+
+	if len(cfg.Groups) == 0 && len(cfg.Hosts) == 0 {
+		return ERR_NO_GROUPHOST
+	}
+
+	set := make(map[string]bool)
+	for _, host := range cfg.Hosts {
+		name := host.NameOrAddress()
+		if _, exists := set[name]; exists {
+			return fmt.Errorf("duplicate host \"%s\"", name)
+		}
+		set[name] = true
+	}
+
+	for group, hosts := range cfg.Groups {
+		set = make(map[string]bool)
+		for _, host := range hosts {
+			name := host.NameOrAddress()
+			if _, exists := set[name]; exists {
+				return fmt.Errorf(
+					"duplicate host \"%s\" in group \"%s\"", group, name,
+				)
+			}
+			set[name] = true
+		}
+	}
+
+	return nil
+}

go.mod

@@ -2,4 +2,7 @@ module git.binarythought.com/cdramey/alrm
 
 go 1.16
 
-require golang.org/x/net v0.0.0-20201224014010-6772e930b67b
+require (
+	golang.org/x/net v0.0.0-20201224014010-6772e930b67b
+	gopkg.in/yaml.v2 v2.4.0
+)

go.sum

@@ -5,3 +5,7 @@ golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
+gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=