Log successful /health requests at Trace lvl

Adds `STEP_LOGGER_ONLY_TRACE_HEALTH_ENDPOINT` environment variable to
opt-in to only logging successful /health requests at the Trace level

Fixes #420

Signed-off-by: Dominic Evans <dominic.evans@uk.ibm.com>

logging/handler_test.go

@@ -0,0 +1,145 @@
+package logging
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/smallstep/assert"
+
+	"github.com/sirupsen/logrus"
+	"github.com/sirupsen/logrus/hooks/test"
+)
+
+// TestHealthOKHandling ensures that http requests from the Kubernetes
+// liveness/readiness probes are only logged at Trace level if they are HTTP
+// 200 (which is normal operation) and the user has opted-in. If the user has
+// not opted-in then they continue to be logged at Info level.
+func TestHealthOKHandling(t *testing.T) {
+	statusHandler := func(statusCode int) http.HandlerFunc {
+		return func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(statusCode)
+			fmt.Fprint(w, "{}")
+		}
+	}
+
+	tests := []struct {
+		name    string
+		path    string
+		options options
+		handler http.HandlerFunc
+		want    logrus.Level
+	}{
+		{
+			name:    "200 should be logged at Info level for /health request without explicit opt-in",
+			path:    "/health",
+			handler: statusHandler(http.StatusOK),
+			want:    logrus.InfoLevel,
+		},
+		{
+			name: "200 should be logged only at Trace level for /health request if opt-in",
+			path: "/health",
+			options: options{
+				onlyTraceHealthEndpoint: true,
+			},
+			handler: statusHandler(http.StatusOK),
+			want:    logrus.TraceLevel,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			logger, hook := test.NewNullLogger()
+			logger.SetLevel(logrus.TraceLevel)
+			l := &LoggerHandler{
+				logger:  logger,
+				options: tt.options,
+				next:    tt.handler,
+			}
+
+			r := httptest.NewRequest("GET", tt.path, nil)
+			w := httptest.NewRecorder()
+			l.ServeHTTP(w, r)
+
+			if assert.Equals(t, 1, len(hook.AllEntries())) {
+				assert.Equals(t, tt.want, hook.LastEntry().Level)
+			}
+		})
+	}
+}
+
+// TestHandlingRegardlessOfOptions ensures that http requests are treated like
+// any other request if they are for a non-health uri or fall within the
+// warn/error ranges of the http status codes, regardless of the
+// "onlyTraceHealthEndpoint" option.
+func TestHandlingRegardlessOfOptions(t *testing.T) {
+	statusHandler := func(statusCode int) http.HandlerFunc {
+		return func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(statusCode)
+			fmt.Fprint(w, "{}")
+		}
+	}
+
+	tests := []struct {
+		name    string
+		path    string
+		handler http.HandlerFunc
+		want    logrus.Level
+	}{
+		{
+			name:    "200 should be logged at Info level for non-health requests",
+			path:    "/info",
+			handler: statusHandler(http.StatusOK),
+			want:    logrus.InfoLevel,
+		},
+		{
+			name:    "400 should be logged at Warn level for non-health requests",
+			path:    "/info",
+			handler: statusHandler(http.StatusBadRequest),
+			want:    logrus.WarnLevel,
+		},
+		{
+			name:    "500 should be logged at Error level for non-health requests",
+			path:    "/info",
+			handler: statusHandler(http.StatusInternalServerError),
+			want:    logrus.ErrorLevel,
+		},
+		{
+			name:    "400 should be logged at Warn level even for /health requests",
+			path:    "/health",
+			handler: statusHandler(http.StatusBadRequest),
+			want:    logrus.WarnLevel,
+		},
+		{
+			name:    "500 should be logged at Error level even for /health requests",
+			path:    "/health",
+			handler: statusHandler(http.StatusInternalServerError),
+			want:    logrus.ErrorLevel,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			for _, b := range []bool{true, false} {
+				logger, hook := test.NewNullLogger()
+				logger.SetLevel(logrus.TraceLevel)
+				l := &LoggerHandler{
+					logger: logger,
+					options: options{
+						onlyTraceHealthEndpoint: b,
+					},
+					next: tt.handler,
+				}
+
+				r := httptest.NewRequest("GET", tt.path, nil)
+				w := httptest.NewRecorder()
+				l.ServeHTTP(w, r)
+
+				if assert.Equals(t, 1, len(hook.AllEntries())) {
+					assert.Equals(t, tt.want, hook.LastEntry().Level)
+				}
+			}
+		})
+	}
+}