Add Logstash 6 compatibility for health check

cmd/health.go

@@ -180,6 +180,16 @@ var healthCmd = &cobra.Command{
 			check.ExitError(err)
 		}
 
+		// Enable some backwards compatibility
+		// Can be changed to a switch statement in the future,
+		// when more versions need special cases
+		// For Logstash 6, we assume a parsed JSON response
+		// is enough to declare the instance running, since there
+		// is no status field.
+		if stat.MajorVersion == 6 {
+			stat.Status = "green"
+		}
+
 		// Logstash Health Status
 		switch stat.Status {
 		default:

cmd/health_test.go

@@ -29,6 +29,47 @@ type HealthTest struct {
 	expected string
 }
 
+func TestHealthCmd_Logstash6(t *testing.T) {
+	tests := []HealthTest{
+		{
+			name: "version-error",
+			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+				w.Write([]byte(`{"host":"logstash","version":"foo"}`))
+			})),
+			args:     []string{"run", "../main.go", "health"},
+			expected: "UNKNOWN - Could not determine version",
+		},
+		{
+			name: "health-ok",
+			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+				w.Write([]byte(`{"host":"logstash","version":"6.8.23","http_address":"0.0.0.0:9600","id":"123","name":"logstash","jvm":{"threads":{"count":1,"peak_count":2},"mem":{},"gc":{},"uptime_in_millis":123},"process":{},"events":{},"pipelines":{"main":{}},"reloads":{"failures":0,"successes":0},"os":{}}`))
+			})),
+			args:     []string{"run", "../main.go", "health"},
+			expected: "OK - Logstash is healthy",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			defer test.server.Close()
+
+			// We need the random Port extracted
+			u, _ := url.Parse(test.server.URL)
+			cmd := exec.Command("go", append(test.args, "--port", u.Port())...)
+			out, _ := cmd.CombinedOutput()
+
+			actual := string(out)
+
+			if !strings.Contains(actual, test.expected) {
+				t.Error("\nActual: ", actual, "\nExpected: ", test.expected)
+			}
+
+		})
+	}
+}
+
 func TestHealthCmd_Logstash7(t *testing.T) {
 	tests := []HealthTest{
 		{

internal/logstash/api.go

@@ -1,5 +1,12 @@
 package logstash
 
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
 // https://www.elastic.co/guide/en/logstash/current/node-stats-api.html
 
 type Pipeline struct {
@@ -44,9 +51,40 @@ type JVM struct {
 }
 
 type Stat struct {
-	Host    string  `json:"host"`
-	Version string  `json:"version"`
-	Status  string  `json:"status"`
-	Process Process `json:"process"`
-	Jvm     JVM     `json:"jvm"`
+	Host         string  `json:"host"`
+	Version      string  `json:"version"`
+	Status       string  `json:"status"`
+	Process      Process `json:"process"`
+	Jvm          JVM     `json:"jvm"`
+	MajorVersion int
+}
+
+// Custom Unmarshal since we might want to add or parse
+// further fields in the future. This is simpler to extend and
+// to test here than during the CheckPlugin logic.
+func (s *Stat) UnmarshalJSON(b []byte) error {
+	type Temp Stat
+
+	t := (*Temp)(s)
+
+	err := json.Unmarshal(b, t)
+
+	if err != nil {
+		return err
+	}
+
+	// Could also use some semver package,
+	// but decided against the depedency
+	if s.Version != "" {
+		v := strings.Split(s.Version, ".")
+		majorVersion, convErr := strconv.Atoi(v[0])
+
+		if convErr != nil {
+			return fmt.Errorf("Could not determine version")
+		}
+
+		s.MajorVersion = majorVersion
+	}
+
+	return nil
 }