chore: drop github per user rate limit tracking (#12286)

* chore: drop github per user rate limit tracking

Rate limits for authenticated requests are per user.
This would be an excessive number of prometheus labels,
so we only track the unauthorized limit.

coderd/promoauth/github.go

@@ -16,12 +16,24 @@ type rateLimits struct {
 	Resource  string
 }
 
-// githubRateLimits checks the returned response headers and
+// githubRateLimits returns rate limit information from a GitHub response.
+// GitHub rate limits are on a per-user basis, and tracking each user as
+// a prometheus label might be too much. So only track rate limits for
+// unauthorized responses.
+//
+// Unauthorized responses have a much stricter rate limit of 60 per hour.
+// Tracking this is vital to ensure we do not hit the limit.
 func githubRateLimits(resp *http.Response, err error) (rateLimits, bool) {
 	if err != nil || resp == nil {
 		return rateLimits{}, false
 	}
 
+	// Only track 401 responses which indicates we are using the 60 per hour
+	// rate limit.
+	if resp.StatusCode != http.StatusUnauthorized {
+		return rateLimits{}, false
+	}
+
 	p := headerParser{header: resp.Header}
 	// See
 	// https://docs.github.com/en/rest/using-the-rest-api/rate-limits-for-the-rest-api?apiVersion=2022-11-28#checking-the-status-of-your-rate-limit
@@ -29,7 +41,7 @@ func githubRateLimits(resp *http.Response, err error) (rateLimits, bool) {
 		Limit:     p.int("x-ratelimit-limit"),
 		Remaining: p.int("x-ratelimit-remaining"),
 		Used:      p.int("x-ratelimit-used"),
-		Resource:  p.string("x-ratelimit-resource"),
+		Resource:  p.string("x-ratelimit-resource") + "-unauthorized",
 	}
 
 	if limits.Limit == 0 &&
@@ -50,18 +62,6 @@ func githubRateLimits(resp *http.Response, err error) (rateLimits, bool) {
 	}
 	limits.Reset = resetAt
 
-	// Unauthorized requests have their own rate limit, so we should
-	// track them separately.
-	if resp.StatusCode == http.StatusUnauthorized {
-		limits.Resource += "-unauthorized"
-	}
-
-	// A 401 or 429 means too many requests. This might mess up the
-	// "resource" string because we could hit the unauthorized limit,
-	// and we do not want that to override the authorized one.
-	// However, in testing, it seems a 401 is always a 401, even if
-	// the limit is hit.
-
 	if len(p.errors) > 0 {
 		// If we are missing any headers, then do not try and guess
 		// what the rate limits are.

coderd/promoauth/oauth2_test.go

@@ -179,6 +179,15 @@ func TestGithubRateLimits(t *testing.T) {
 							}
 						}
 
+						// Ignore the well known, required for setup
+						if !strings.Contains(r.URL.String(), ".well-known") {
+							// GitHub rate limits only are instrumented for unauthenticated calls. So emulate
+							// that here. We cannot actually use invalid credentials because the fake IDP
+							// will throw a test error, as it only expects things to work. And we want to use
+							// a real idp to emulate the right http calls to be instrumented.
+							rw.WriteHeader(http.StatusUnauthorized)
+							return
+						}
 						next.ServeHTTP(rw, r)
 					})
 				}))
@@ -195,13 +204,13 @@ func TestGithubRateLimits(t *testing.T) {
 			// Do a single oauth2 call
 			ctx := testutil.Context(t, testutil.WaitShort)
 			ctx = context.WithValue(ctx, oauth2.HTTPClient, idp.HTTPClient(nil))
-			_, err := cfg.Exchange(ctx, idp.CreateAuthCode(t, "foo"))
-			require.NoError(t, err)
+			_, err := cfg.Exchange(ctx, "invalid")
+			require.Error(t, err, "expected unauthorized exchange")
 
 			// Verify
 			labels := prometheus.Labels{
 				"name":     "test",
-				"resource": "core",
+				"resource": "core-unauthorized",
 			}
 			pass := true
 			if !c.ExpectNoMetrics {

scripts/metricsdocgen/metrics

@@ -12,8 +12,8 @@ coderd_oauth2_external_requests_rate_limit_reset_in_seconds{name="primary-github
 coderd_oauth2_external_requests_rate_limit_reset_in_seconds{name="secondary-github",resource="core"} 121.82186601
 # HELP coderd_oauth2_external_requests_rate_limit_total The total number of allowed requests per interval.
 # TYPE coderd_oauth2_external_requests_rate_limit_total gauge
-coderd_oauth2_external_requests_rate_limit_total{name="primary-github",resource="core"} 5000
-coderd_oauth2_external_requests_rate_limit_total{name="secondary-github",resource="core"} 5000
+coderd_oauth2_external_requests_rate_limit_total{name="primary-github",resource="core-unauthorized"} 5000
+coderd_oauth2_external_requests_rate_limit_total{name="secondary-github",resource="core-unauthorized"} 5000
 # HELP coderd_oauth2_external_requests_rate_limit_used The number of requests made in this interval.
 # TYPE coderd_oauth2_external_requests_rate_limit_used gauge
 coderd_oauth2_external_requests_rate_limit_used{name="primary-github",resource="core"} 148