fix(backup): don't allow for incomplete backup

Backward compatibility is less important than correctness.
It forces us to skip backup of system_traces and system_distributed
keyspaces when testing a single dc backup.

Fixes #3922

pkg/service/backup/model.go

@@ -539,21 +539,6 @@ type tokenRangesValidator struct {
 }
 
 func (v tokenRangesValidator) validate(ks, tab string, ring scyllaclient.Ring) error {
-	// Skip validation for SimpleStrategy when all hosts from backed up dcs are live
-	// in order to preserve backward compatibility (#3922).
-	if ring.Replication == scyllaclient.SimpleStrategy {
-		missingHost := false
-		for h, dc := range ring.HostDC {
-			if v.dcs.Has(dc) && !v.liveNodes.Has(h) {
-				missingHost = true
-				break
-			}
-		}
-		if !missingHost {
-			return nil
-		}
-	}
-
 	for _, rt := range ring.ReplicaTokens {
 		if !v.liveNodes.HasAny(rt.ReplicaSet...) {
 			return errors.Errorf("%s.%s: the whole replica set %v is filtered out, so the data owned by it can't be backed up", ks, tab, rt.ReplicaSet)

pkg/service/backup/testdata/get_target/filter_dc.golden.json

@@ -10,34 +10,13 @@
       ],
       "all_tables": true
     },
-    {
-      "keyspace": "system_distributed",
-      "tables": [
-        "cdc_generation_timestamps",
-        "cdc_streams_descriptions_v2",
-        "service_levels",
-        "view_build_status"
-      ],
-      "all_tables": true
-    },
     {
       "keyspace": "system_distributed_everywhere",
       "tables": [
         "cdc_generation_descriptions_v2"
       ],
       "all_tables": true
     },
-    {
-      "keyspace": "system_traces",
-      "tables": [
-        "node_slow_log_time_idx",
-        "node_slow_log",
-        "events",
-        "sessions_time_idx",
-        "sessions"
-      ],
-      "all_tables": true
-    },
     {
       "keyspace": "system_schema",
       "tables": [

pkg/service/backup/testdata/get_target/filter_dc.input.json

@@ -1 +1 @@
-{"dc": ["dc1"], "location": ["s3:backuptest-get-target"]}
+{"dc": ["dc1"], "location": ["s3:backuptest-get-target"], "keyspace":  ["*", "!system_traces", "!system_distributed"]}