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tsweb: add request ID for errors

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If an optional request ID generating func is supplied to StdHandler,
then requests that return an error will be logged with a request ID that
is also shown as part of the response.

Updates tailscale/corp#2549

Change-Id: Ic7499706df42f95b6878d44d4aab253e2fc6a69b
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>
This commit is contained in:
Adrian Dewhurst 2023-08-11 16:41:58 -04:00 committed by Adrian Dewhurst
parent cf31b58ed1
commit f75a36f9bc
3 changed files with 286 additions and 14 deletions
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6
tsweb/log.go
View File

@ -45,6 +45,12 @@ type AccessLogRecord struct {
Bytes int `json:"bytes,omitempty"`
// Error encountered during request processing.
Err string `json:"err,omitempty"`
// RequestID is a unique ID for this request. When a request fails due to an
// error, the ID is generated and displayed to the client immediately after
// the error text, as well as logged here. This makes it easier to correlate
// support requests with server logs. If a RequestID generator is not
// configured, RequestID will be empty.
RequestID RequestID `json:"request_id,omitempty"`
}
// String returns m as a JSON string.

56
tsweb/tsweb.go
View File

@ -169,7 +169,8 @@ type ReturnHandler interface {
type HandlerOptions struct {
QuietLoggingIfSuccessful bool // if set, do not log successfully handled HTTP requests (200 and 304 status codes)
Logf logger.Logf
Now func() time.Time // if nil, defaults to time.Now
Now func() time.Time // if nil, defaults to time.Now
GenerateRequestID func(*http.Request) RequestID // if nil, no request IDs are generated
// If non-nil, StatusCodeCounters maintains counters
// of status codes for handled responses.
@ -266,6 +267,11 @@ func (h retHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
msg.Code = 499 // nginx convention: Client Closed Request
msg.Err = context.Canceled.Error()
case hErrOK:
if hErr.RequestID == "" && h.opts.GenerateRequestID != nil {
hErr.RequestID = h.opts.GenerateRequestID(r)
}
msg.RequestID = hErr.RequestID
// Handler asked us to send an error. Do so, if we haven't
// already sent a response.
msg.Err = hErr.Msg
@ -296,14 +302,24 @@ func (h retHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
}
lw.WriteHeader(msg.Code)
fmt.Fprintln(lw, hErr.Msg)
if hErr.RequestID != "" {
fmt.Fprintln(lw, hErr.RequestID)
}
}
case err != nil:
const internalServerError = "internal server error"
errorMessage := internalServerError
if h.opts.GenerateRequestID != nil {
msg.RequestID = h.opts.GenerateRequestID(r)
errorMessage = errorMessage + "\n" + string(msg.RequestID)
}
// Handler returned a generic error. Serve an internal server
// error, if necessary.
msg.Err = err.Error()
if lw.code == 0 {
msg.Code = http.StatusInternalServerError
http.Error(lw, "internal server error", msg.Code)
http.Error(lw, errorMessage, msg.Code)
}
}
@ -398,18 +414,44 @@ func (l loggingResponseWriter) Flush() {
f.Flush()
}
// RequestID is an opaque identifier for a HTTP request, used to correlate
// user-visible errors with backend server logs. If present in a HTTPError, the
// RequestID will be printed alongside the message text and logged in the
// AccessLogRecord. If an HTTPError has no RequestID (or a non-HTTPError error
// is returned), but the StdHandler has a RequestID generator function, then a
// RequestID will be generated before responding to the client and logging the
// error.
//
// In the event that there is no ErrorHandlerFunc and a non-HTTPError is
// returned to a StdHandler, the response body will be formatted like
// "internal server error\n{RequestID}\n".
//
// There is no particular format required for a RequestID, but ideally it should
// be obvious to an end-user that it is something to record for support
// purposes. One possible example for a RequestID format is:
// REQ-{server identifier}-{timestamp}-{random hex string}.
type RequestID string
// HTTPError is an error with embedded HTTP response information.
//
// It is the error type to be (optionally) used by Handler.ServeHTTPReturn.
type HTTPError struct {
Code int // HTTP response code to send to client; 0 means 500
Msg string // Response body to send to client
Err error // Detailed error to log on the server
Header http.Header // Optional set of HTTP headers to set in the response
Code int // HTTP response code to send to client; 0 means 500
Msg string // Response body to send to client
Err error // Detailed error to log on the server
RequestID RequestID // Optional identifier to connect client-visible errors with server logs
Header http.Header // Optional set of HTTP headers to set in the response
}
// Error implements the error interface.
func (e HTTPError) Error() string { return fmt.Sprintf("httperror{%d, %q, %v}", e.Code, e.Msg, e.Err) }
func (e HTTPError) Error() string {
if e.RequestID != "" {
return fmt.Sprintf("httperror{%d, %q, %v, RequestID=%q}", e.Code, e.Msg, e.Err, e.RequestID)
} else {
// Backwards compatibility
return fmt.Sprintf("httperror{%d, %q, %v}", e.Code, e.Msg, e.Err)
}
}
func (e HTTPError) Unwrap() error { return e.Err }

238
tsweb/tsweb_test.go
View File

@ -38,6 +38,7 @@ func (f handlerFunc) ServeHTTPReturn(w http.ResponseWriter, r *http.Request) err
}
func TestStdHandler(t *testing.T) {
const exampleRequestID = "example-request-id"
var (
handlerCode = func(code int) ReturnHandler {
return handlerFunc(func(w http.ResponseWriter, r *http.Request) error {
@ -66,16 +67,20 @@ func TestStdHandler(t *testing.T) {
bgCtx = context.Background()
// canceledCtx, cancel = context.WithCancel(bgCtx)
startTime = time.Unix(1687870000, 1234)
setExampleRequestID = func(_ *http.Request) RequestID { return exampleRequestID }
)
// cancel()
tests := []struct {
name string
rh ReturnHandler
r *http.Request
errHandler ErrorHandlerFunc
wantCode int
wantLog AccessLogRecord
name string
rh ReturnHandler
r *http.Request
errHandler ErrorHandlerFunc
generateRequestID func(*http.Request) RequestID
wantCode int
wantLog AccessLogRecord
wantBody string
}{
{
name: "handler returns 200",
@ -94,6 +99,24 @@ func TestStdHandler(t *testing.T) {
},
},
{
name: "handler returns 200 with request ID",
rh: handlerCode(200),
r: req(bgCtx, "http://example.com/"),
generateRequestID: setExampleRequestID,
wantCode: 200,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
TLS: false,
Host: "example.com",
Method: "GET",
Code: 200,
RequestURI: "/",
},
},
{
name: "handler returns 404",
rh: handlerCode(404),
@ -110,6 +133,23 @@ func TestStdHandler(t *testing.T) {
},
},
{
name: "handler returns 404 with request ID",
rh: handlerCode(404),
r: req(bgCtx, "http://example.com/foo"),
generateRequestID: setExampleRequestID,
wantCode: 404,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
Host: "example.com",
Method: "GET",
RequestURI: "/foo",
Code: 404,
},
},
{
name: "handler returns 404 via HTTPError",
rh: handlerErr(0, Error(404, "not found", testErr)),
@ -125,6 +165,27 @@ func TestStdHandler(t *testing.T) {
Err: "not found: " + testErr.Error(),
Code: 404,
},
wantBody: "not found\n",
},
{
name: "handler returns 404 via HTTPError with request ID",
rh: handlerErr(0, Error(404, "not found", testErr)),
r: req(bgCtx, "http://example.com/foo"),
generateRequestID: setExampleRequestID,
wantCode: 404,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
Host: "example.com",
Method: "GET",
RequestURI: "/foo",
Err: "not found: " + testErr.Error(),
Code: 404,
RequestID: exampleRequestID,
},
wantBody: "not found\n" + exampleRequestID + "\n",
},
{
@ -142,6 +203,27 @@ func TestStdHandler(t *testing.T) {
Err: "not found",
Code: 404,
},
wantBody: "not found\n",
},
{
name: "handler returns 404 with request ID and nil child error",
rh: handlerErr(0, Error(404, "not found", nil)),
r: req(bgCtx, "http://example.com/foo"),
generateRequestID: setExampleRequestID,
wantCode: 404,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
Host: "example.com",
Method: "GET",
RequestURI: "/foo",
Err: "not found",
Code: 404,
RequestID: exampleRequestID,
},
wantBody: "not found\n" + exampleRequestID + "\n",
},
{
@ -159,6 +241,27 @@ func TestStdHandler(t *testing.T) {
Err: "visible error",
Code: 500,
},
wantBody: "visible error\n",
},
{
name: "handler returns user-visible error with request ID",
rh: handlerErr(0, vizerror.New("visible error")),
r: req(bgCtx, "http://example.com/foo"),
generateRequestID: setExampleRequestID,
wantCode: 500,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
Host: "example.com",
Method: "GET",
RequestURI: "/foo",
Err: "visible error",
Code: 500,
RequestID: exampleRequestID,
},
wantBody: "visible error\n" + exampleRequestID + "\n",
},
{
@ -176,6 +279,27 @@ func TestStdHandler(t *testing.T) {
Err: "visible error",
Code: 500,
},
wantBody: "visible error\n",
},
{
name: "handler returns user-visible error wrapped by private error with request ID",
rh: handlerErr(0, fmt.Errorf("private internal error: %w", vizerror.New("visible error"))),
r: req(bgCtx, "http://example.com/foo"),
generateRequestID: setExampleRequestID,
wantCode: 500,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
Host: "example.com",
Method: "GET",
RequestURI: "/foo",
Err: "visible error",
Code: 500,
RequestID: exampleRequestID,
},
wantBody: "visible error\n" + exampleRequestID + "\n",
},
{
@ -193,6 +317,27 @@ func TestStdHandler(t *testing.T) {
Err: testErr.Error(),
Code: 500,
},
wantBody: "internal server error\n",
},
{
name: "handler returns generic error with request ID",
rh: handlerErr(0, testErr),
r: req(bgCtx, "http://example.com/foo"),
generateRequestID: setExampleRequestID,
wantCode: 500,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
Host: "example.com",
Method: "GET",
RequestURI: "/foo",
Err: testErr.Error(),
Code: 500,
RequestID: exampleRequestID,
},
wantBody: "internal server error\n" + exampleRequestID + "\n",
},
{
@ -212,6 +357,25 @@ func TestStdHandler(t *testing.T) {
},
},
{
name: "handler returns error after writing response with request ID",
rh: handlerErr(200, testErr),
r: req(bgCtx, "http://example.com/foo"),
generateRequestID: setExampleRequestID,
wantCode: 200,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
Host: "example.com",
Method: "GET",
RequestURI: "/foo",
Err: testErr.Error(),
Code: 200,
RequestID: exampleRequestID,
},
},
{
name: "handler returns HTTPError after writing response",
rh: handlerErr(200, Error(404, "not found", testErr)),
@ -267,6 +431,7 @@ func TestStdHandler(t *testing.T) {
Code: 101,
},
},
{
name: "error handler gets run",
rh: handlerErr(0, Error(404, "not found", nil)), // status code changed in errHandler
@ -286,6 +451,62 @@ func TestStdHandler(t *testing.T) {
Err: "not found",
RequestURI: "/",
},
wantBody: "not found\n",
},
{
name: "error handler gets run with request ID",
rh: handlerErr(0, Error(404, "not found", nil)), // status code changed in errHandler
r: req(bgCtx, "http://example.com/"),
generateRequestID: setExampleRequestID,
wantCode: 200,
errHandler: func(w http.ResponseWriter, r *http.Request, e HTTPError) {
http.Error(w, fmt.Sprintf("%s with request ID %s", e.Msg, e.RequestID), 200)
},
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
TLS: false,
Host: "example.com",
Method: "GET",
Code: 404,
Err: "not found",
RequestURI: "/",
RequestID: exampleRequestID,
},
wantBody: "not found with request ID " + exampleRequestID + "\n",
},
{
name: "request ID can use information from request",
rh: handlerErr(0, Error(400, "bad request", nil)),
r: func() *http.Request {
r := req(bgCtx, "http://example.com/")
r.AddCookie(&http.Cookie{Name: "want_request_id", Value: "asdf1234"})
return r
}(),
generateRequestID: func(r *http.Request) RequestID {
c, _ := r.Cookie("want_request_id")
if c == nil {
return ""
}
return RequestID(c.Value)
},
wantCode: 400,
wantLog: AccessLogRecord{
When: startTime,
Seconds: 1.0,
Proto: "HTTP/1.1",
TLS: false,
Host: "example.com",
RequestURI: "/",
Method: "GET",
Code: 400,
Err: "bad request",
RequestID: "asdf1234",
},
wantBody: "bad request\nasdf1234\n",
},
}
@ -305,7 +526,7 @@ func TestStdHandler(t *testing.T) {
})
rec := noopHijacker{httptest.NewRecorder(), false}
h := StdHandler(test.rh, HandlerOptions{Logf: logf, Now: clock.Now, OnError: test.errHandler})
h := StdHandler(test.rh, HandlerOptions{Logf: logf, Now: clock.Now, GenerateRequestID: test.generateRequestID, OnError: test.errHandler})
h.ServeHTTP(&rec, test.r)
res := rec.Result()
if res.StatusCode != test.wantCode {
@ -324,6 +545,9 @@ func TestStdHandler(t *testing.T) {
if diff := cmp.Diff(logs[0], test.wantLog, errTransform); diff != "" {
t.Errorf("handler wrote incorrect request log (-got+want):\n%s", diff)
}
if diff := cmp.Diff(rec.Body.String(), test.wantBody); diff != "" {
t.Errorf("handler wrote incorrect body (-got+want):\n%s", diff)
}
})
}
}