Merge federationapi, federationsender, signingkeyserver components (#2055)

* Initial federation sender -> federation API refactoring

* Move base into own package, avoids import cycle

* Fix build errors

* Fix tests

* Add signing key server tables

* Try to fold signing key server into federation API

* Fix dendritejs builds

* Update embedded interfaces

* Fix panic, fix lint error

* Update configs, docker

* Rename some things

* Reuse same keyring on the implementing side

* Fix federation tests, `NewBaseDendrite` can accept freeform options

* Fix build

* Update create_db, configs

* Name tables back

* Don't rename federationsender consumer for now

federationapi/statistics/statistics_test.go

@@ -0,0 +1,64 @@
+package statistics
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+func TestBackoff(t *testing.T) {
+	stats := Statistics{
+		FailuresUntilBlacklist: 7,
+	}
+	server := ServerStatistics{
+		statistics: &stats,
+		serverName: "test.com",
+	}
+
+	// Start by checking that counting successes works.
+	server.Success()
+	if successes := server.SuccessCount(); successes != 1 {
+		t.Fatalf("Expected success count 1, got %d", successes)
+	}
+
+	// Register a failure.
+	server.Failure()
+
+	t.Logf("Backoff counter: %d", server.backoffCount.Load())
+
+	// Now we're going to simulate backing off a few times to see
+	// what happens.
+	for i := uint32(1); i <= 10; i++ {
+		// Register another failure for good measure. This should have no
+		// side effects since a backoff is already in progress. If it does
+		// then we'll fail.
+		until, blacklisted := server.Failure()
+
+		// Get the duration.
+		_, blacklist := server.BackoffInfo()
+		duration := time.Until(until).Round(time.Second)
+
+		// Unset the backoff, or otherwise our next call will think that
+		// there's a backoff in progress and return the same result.
+		server.cancel()
+		server.backoffStarted.Store(false)
+
+		// Check if we should be blacklisted by now.
+		if i >= stats.FailuresUntilBlacklist {
+			if !blacklist {
+				t.Fatalf("Backoff %d should have resulted in blacklist but didn't", i)
+			} else if blacklist != blacklisted {
+				t.Fatalf("BackoffInfo and Failure returned different blacklist values")
+			} else {
+				t.Logf("Backoff %d is blacklisted as expected", i)
+				continue
+			}
+		}
+
+		// Check if the duration is what we expect.
+		t.Logf("Backoff %d is for %s", i, duration)
+		if wanted := time.Second * time.Duration(math.Exp2(float64(i))); !blacklist && duration != wanted {
+			t.Fatalf("Backoff %d should have been %s but was %s", i, wanted, duration)
+		}
+	}
+}