Resolve TestAkamaiPurgerDrainQueueFails race (#6844)

Fixes https://github.com/letsencrypt/boulder/issues/6837

test/integration/akamai_purger_drain_queue_test.go

@@ -77,21 +77,31 @@ func TestAkamaiPurgerDrainQueueFails(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
+	// We know that the purger is configured to only process two items per batch,
+	// so submitting 10 items should give it enough of a backlog to guarantee
+	// that our SIGTERM reaches the process before it's fully cleared the queue.
+	for i := 0; i < 10; i++ {
 		_, err = purgerClient.Purge(context.Background(), &akamaipb.PurgeRequest{
-		Urls: []string{"http://example.com/"},
+			Urls: []string{fmt.Sprintf("http://example%d.com/", i)},
 		})
 		if err != nil {
 			// Don't use t.Fatal here because we need to get as far as the SIGTERM or
 			// we'll hang on exit.
 			t.Error(err)
 		}
+	}
 
 	purgerCmd.Process.Signal(syscall.SIGTERM)
 	err = purgerCmd.Wait()
 	if err == nil {
 		t.Error("expected error shutting down akamai-purger that could not reach backend")
 	}
-	test.AssertContains(t, outputBuffer.String(), "failed to purge OCSP responses for 1 certificates before exit: all attempts to submit purge request failed")
+
+	// Use two asserts because we're not sure what integer (10? 8?) will come in
+	// the middle of the error message.
+	test.AssertContains(t, outputBuffer.String(), "failed to purge OCSP responses for")
+	test.AssertContains(t, outputBuffer.String(), "certificates before exit: all attempts to submit purge request failed")
 }
 
 func TestAkamaiPurgerDrainQueueSucceeds(t *testing.T) {

test/integration/testdata/akamai-purger-queue-drain-config.json

@@ -3,6 +3,10 @@
 		"debugAddr": ":9766",
 		"purgeRetries": 10,
 		"purgeRetryBackoff": "50ms",
+		"throughput": {
+			"queueEntriesPerBatch": 2,
+			"purgeBatchInterval": "32ms"
+		},
 		"baseURL": "http://localhost:6889",
 		"clientToken": "its-a-token",
 		"clientSecret": "its-a-secret",
@@ -15,15 +19,23 @@
 		},
 		"grpc": {
 			"address": ":9199",
+			"maxConnectionAge": "30s",
+			"services": {
+				"akamai.AkamaiPurger": {
 					"clientNames": [
-            "health-checker.boulder",
 						"ra.boulder"
 					]
+				},
+				"grpc.health.v1.Health": {
+					"clientNames": [
+						"health-checker.boulder"
+					]
+				}
+			}
 		}
 	},
-
 	"syslog": {
 		"stdoutlevel": 6,
-      "sysloglevel": 6
+		"sysloglevel": -1
 	}
 }