20540: Implement nearly-full jitter for exponential backoff.

[arvados.git] / sdk / go / arvados / client_test.go

diff --git a/sdk/go/arvados/client_test.go b/sdk/go/arvados/client_test.go
index 422aca9f68f9cdf47612170a1feee6416d89e389..b1aae00daf42fd860be2ecbbbf131f108a4be8bd 100644 (file)
--- a/sdk/go/arvados/client_test.go
+++ b/sdk/go/arvados/client_test.go
@@ -9,6 +9,7 @@ import (
        "context"
        "fmt"
        "io/ioutil"
+       "math"
        "math/rand"
        "net/http"
        "net/http/httptest"
@@ -339,3 +340,61 @@ func (s *clientRetrySuite) TestContextAlreadyCanceled(c *check.C) {
        err := s.client.RequestAndDecodeContext(ctx, &struct{}{}, http.MethodGet, "test", nil, nil)
        c.Check(err, check.Equals, context.Canceled)
 }
+
+func (s *clientRetrySuite) TestExponentialBackoff(c *check.C) {
+       var min, max time.Duration
+       min, max = time.Second, 64*time.Second
+
+       t := exponentialBackoff(min, max, 0, nil)
+       c.Check(t, check.Equals, min)
+
+       for e := float64(1); e < 5; e += 1 {
+               ok := false
+               for i := 0; i < 20; i++ {
+                       t = exponentialBackoff(min, max, int(e), nil)
+                       // Every returned value must be between min and min(2^e, max)
+                       c.Check(t >= min, check.Equals, true)
+                       c.Check(t <= min*time.Duration(math.Pow(2, e)), check.Equals, true)
+                       c.Check(t <= max, check.Equals, true)
+                       // Check that jitter is actually happening by
+                       // checking that at least one in 20 trials is
+                       // between min*2^(e-.75) and min*2^(e-.25)
+                       jittermin := time.Duration(float64(min) * math.Pow(2, e-0.75))
+                       jittermax := time.Duration(float64(min) * math.Pow(2, e-0.25))
+                       c.Logf("min %v max %v e %v jittermin %v jittermax %v t %v", min, max, e, jittermin, jittermax, t)
+                       if t > jittermin && t < jittermax {
+                               ok = true
+                               break
+                       }
+               }
+               c.Check(ok, check.Equals, true)
+       }
+
+       for i := 0; i < 20; i++ {
+               t := exponentialBackoff(min, max, 100, nil)
+               c.Check(t < max, check.Equals, true)
+       }
+
+       for _, trial := range []struct {
+               retryAfter string
+               expect     time.Duration
+       }{
+               {"1", time.Second * 4},             // minimum enforced
+               {"5", time.Second * 5},             // header used
+               {"55", time.Second * 10},           // maximum enforced
+               {"eleventy-nine", time.Second * 4}, // invalid header, exponential backoff used
+               {time.Now().UTC().Add(time.Second).Format(time.RFC1123), time.Second * 4},  // minimum enforced
+               {time.Now().UTC().Add(time.Minute).Format(time.RFC1123), time.Second * 10}, // maximum enforced
+               {time.Now().UTC().Add(-time.Minute).Format(time.RFC1123), time.Second * 4}, // minimum enforced
+       } {
+               c.Logf("trial %+v", trial)
+               t := exponentialBackoff(time.Second*4, time.Second*10, 0, &http.Response{
+                       StatusCode: http.StatusTooManyRequests,
+                       Header:     http.Header{"Retry-After": {trial.retryAfter}}})
+               c.Check(t, check.Equals, trial.expect)
+       }
+       t = exponentialBackoff(time.Second*4, time.Second*10, 0, &http.Response{
+               StatusCode: http.StatusTooManyRequests,
+       })
+       c.Check(t, check.Equals, time.Second*4)
+}