Merge 'scylla-gdb.py: introduce scylla tablet-metadata command' from Botond Dénes

Dumps the content of the tablet metadata. Very useful for debugging tablet related problems.

Example output:
```
(gdb) scylla tablet-metadata --table usertable_no_lwt

This node: host_id: b90662a9-98b1-4452-bc45-44d460ecab62, shard: 0

table alternator_usertable_no_lwt.usertable_no_lwt: id: 68316fa0-78ec-11ef-af10-98d4ab71aac4, tablets: 32, resize decision: merge#1, transitions: 0
  tablet#0: last token: -8646911284551352321, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#0, 84d0cb45-1c6c-4870-b727-03db3130641f#0, b933959e-8134-4ba0-8c44-33dbd51170e9#0]
  tablet#1: last token: -8070450532247928833, replicas: [fb0167dc-7a7d-476d-b4a5-4a55a52dadff#0, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#0, ac2fdd20-2f54-4960-9856-27fd07ed38ef#0]
  tablet#2: last token: -7493989779944505345, replicas: [fb0167dc-7a7d-476d-b4a5-4a55a52dadff#1, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#1, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#1]
  tablet#3: last token: -6917529027641081857, replicas: [ac2fdd20-2f54-4960-9856-27fd07ed38ef#1, b933959e-8134-4ba0-8c44-33dbd51170e9#1, 84d0cb45-1c6c-4870-b727-03db3130641f#1]
  tablet#4: last token: -6341068275337658369, replicas: [ac2fdd20-2f54-4960-9856-27fd07ed38ef#2, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#2, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#2]
  tablet#5: last token: -5764607523034234881, replicas: [4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#2, b933959e-8134-4ba0-8c44-33dbd51170e9#2, 84d0cb45-1c6c-4870-b727-03db3130641f#2]
  tablet#6: last token: -5188146770730811393, replicas: [84d0cb45-1c6c-4870-b727-03db3130641f#3, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#3, ac2fdd20-2f54-4960-9856-27fd07ed38ef#3]
  tablet#7: last token: -4611686018427387905, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#3, b933959e-8134-4ba0-8c44-33dbd51170e9#3, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#3]
  tablet#8: last token: -4035225266123964417, replicas: [b933959e-8134-4ba0-8c44-33dbd51170e9#4, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#4, ac2fdd20-2f54-4960-9856-27fd07ed38ef#4]
  tablet#9: last token: -3458764513820540929, replicas: [4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#4, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#4, 84d0cb45-1c6c-4870-b727-03db3130641f#4]
  tablet#10: last token: -2882303761517117441, replicas: [84d0cb45-1c6c-4870-b727-03db3130641f#5, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#5, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#5]
  tablet#11: last token: -2305843009213693953, replicas: [ac2fdd20-2f54-4960-9856-27fd07ed38ef#5, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#5, b933959e-8134-4ba0-8c44-33dbd51170e9#5]
  tablet#12: last token: -1729382256910270465, replicas: [b933959e-8134-4ba0-8c44-33dbd51170e9#6, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#6, 84d0cb45-1c6c-4870-b727-03db3130641f#6]
  tablet#13: last token: -1152921504606846977, replicas: [4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#6, ac2fdd20-2f54-4960-9856-27fd07ed38ef#6, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#6]
  tablet#14: last token: -576460752303423489, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#7, 84d0cb45-1c6c-4870-b727-03db3130641f#7, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#7]
  tablet#15: last token: -1, replicas: [b933959e-8134-4ba0-8c44-33dbd51170e9#7, ac2fdd20-2f54-4960-9856-27fd07ed38ef#7, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#7]
  tablet#16: last token: 576460752303423487, replicas: [ac2fdd20-2f54-4960-9856-27fd07ed38ef#8, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#8, 84d0cb45-1c6c-4870-b727-03db3130641f#8]
  tablet#17: last token: 1152921504606846975, replicas: [b933959e-8134-4ba0-8c44-33dbd51170e9#8, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#8, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#8]
  tablet#18: last token: 1729382256910270463, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#9, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#9, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#9]
  tablet#19: last token: 2305843009213693951, replicas: [84d0cb45-1c6c-4870-b727-03db3130641f#9, ac2fdd20-2f54-4960-9856-27fd07ed38ef#9, b933959e-8134-4ba0-8c44-33dbd51170e9#9]
  tablet#20: last token: 2882303761517117439, replicas: [ac2fdd20-2f54-4960-9856-27fd07ed38ef#10, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#10, b933959e-8134-4ba0-8c44-33dbd51170e9#10]
  tablet#21: last token: 3458764513820540927, replicas: [84d0cb45-1c6c-4870-b727-03db3130641f#10, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#10, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#10]
  tablet#22: last token: 4035225266123964415, replicas: [4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#11, 84d0cb45-1c6c-4870-b727-03db3130641f#11, b933959e-8134-4ba0-8c44-33dbd51170e9#11]
  tablet#23: last token: 4611686018427387903, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#11, ac2fdd20-2f54-4960-9856-27fd07ed38ef#11, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#11]
  tablet#24: last token: 5188146770730811391, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#12, 84d0cb45-1c6c-4870-b727-03db3130641f#12, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#12]
  tablet#25: last token: 5764607523034234879, replicas: [ac2fdd20-2f54-4960-9856-27fd07ed38ef#12, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#12, b933959e-8134-4ba0-8c44-33dbd51170e9#12]
  tablet#26: last token: 6341068275337658367, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#13, b933959e-8134-4ba0-8c44-33dbd51170e9#13, 84d0cb45-1c6c-4870-b727-03db3130641f#13]
  tablet#27: last token: 6917529027641081855, replicas: [ac2fdd20-2f54-4960-9856-27fd07ed38ef#13, fb0167dc-7a7d-476d-b4a5-4a55a52dadff#13, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#13]
  tablet#28: last token: 7493989779944505343, replicas: [b5ddcd7e-45ed-4f20-8841-353bd82cc04c#0, b933959e-8134-4ba0-8c44-33dbd51170e9#0, ac2fdd20-2f54-4960-9856-27fd07ed38ef#0]
  tablet#29: last token: 8070450532247928831, replicas: [fb0167dc-7a7d-476d-b4a5-4a55a52dadff#0, 84d0cb45-1c6c-4870-b727-03db3130641f#0, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#0]
  tablet#30: last token: 8646911284551352319, replicas: [fb0167dc-7a7d-476d-b4a5-4a55a52dadff#1, ac2fdd20-2f54-4960-9856-27fd07ed38ef#1, b5ddcd7e-45ed-4f20-8841-353bd82cc04c#1]
  tablet#31: last token: 9223372036854775807, replicas: [b933959e-8134-4ba0-8c44-33dbd51170e9#1, 4b1e8a42-e8b3-432e-bf7c-b0f7a10eb3cd#1, 84d0cb45-1c6c-4870-b727-03db3130641f#1]
```

The PR includes two marginally related small fixes too.

Improvement, no backport needed.

Closes scylladb/scylladb#20940

* github.com:scylladb/scylladb:
  scylla-gdb.py: add scylla tablet-metadata command
  scylla-gdb.py: register the scylla table command
  scylla-gdb.py: unordered_map: improve flat_hash_map matching

scylla-gdb.py

@@ -651,7 +651,7 @@ class absl_container:
 
 
 def unordered_map(ref):
-    if ref.type.name.startswith('flat_hash_map'):
+    if ref.type.strip_typedefs().name.startswith('flat_hash_map'):
         try:
             return flat_hash_map(ref)
         except gdb.error:
@@ -6109,6 +6109,94 @@ class scylla_repairs(gdb.Command):
         for rm in intrusive_list(gdb.parse_and_eval('debug::repair_meta_for_followers._repair_metas'), link='_tracker_link'):
             self.process("follower", rm)
 
+
+class scylla_tablet_metadata(gdb.Command):
+    """Dump tablet-metadata
+
+    By default, tablet-metadata is dumped for all tables.
+    Tables can be filtered by --keyspace and --table.
+    For more information about usage, see:
+        scylla tablet-metadata --help
+    """
+    _token_bias = 9223372036854775808
+    _max_uint64 = 18446744073709551615
+
+    def _bias(self, n):
+        return n - self._token_bias
+
+    def _last_token_of_compaction_group(self, most_significant_bits, group):
+        if group == ((1 << most_significant_bits) - 1):
+            return self._bias(self._max_uint64)
+        else:
+            return self._bias(((group + 1) << (64 - most_significant_bits)) - 1);
+
+    def __init__(self):
+        gdb.Command.__init__(self, 'scylla tablet-metadata', gdb.COMMAND_USER, gdb.COMPLETE_NONE, True)
+
+    def invoke(self, arg, for_tty):
+        parser = argparse.ArgumentParser(description="scylla tablet-metadata")
+        parser.add_argument("-k", "--keyspace", action="store", type=str,
+                help="Print tablet metadata for tables belonging to the given keyspace")
+        parser.add_argument("-t", "--table", action="store", type=str,
+                help="Print tablet metadata for the given table only (match by name, use together with --keyspace for an exact match)")
+
+        try:
+            args = parser.parse_args(arg.split())
+        except SystemExit:
+            return
+
+        db = find_db()
+        token_metadata = seastar_lw_shared_ptr(db['_shared_token_metadata']['_shared']).get()
+        tablet_metadata = std_unique_ptr(token_metadata['_impl']).get()['_tablets']
+        topology = std_unique_ptr(token_metadata['_impl']).get()['_topology']
+        this_node = topology['_this_node'].dereference()
+
+        gdb.write(f'This node: host_id: {this_node["_host_id"]["id"]}, shard: {current_shard()}\n\n')
+
+        def format_replica_set(replica_set):
+            return ", ".join([f'{replica["host"]["id"]}#{replica["shard"]}' for replica in small_vector(replica_set)])
+
+        tables = {}
+        for table in for_each_table(db):
+            schema = seastar_lw_shared_ptr(table['_schema']).get().dereference()
+            r = schema['_raw']
+            tables[str(r['_id']['id'])] = (str(r['_ks_name'])[1:-1], str(r['_cf_name'])[1:-1])
+
+        for table_id, tablet_map in unordered_map(tablet_metadata['_tablets']):
+            table_id = str(table_id['id'])
+            keyspace_name, table_name = tables[table_id]
+
+            if args.keyspace and keyspace_name != args.keyspace:
+                continue
+
+            if args.table and table_name != args.table:
+                continue
+
+            tablet_map = seastar_lw_shared_ptr(tablet_map['_value']).get()
+            log2_tablets = int(tablet_map['_log2_tablets'])
+            tablet_count = 2 ** log2_tablets
+            resize_decision = std_variant(tablet_map['_resize_decision']['way']).get().type.name.replace('locator::resize_decision::', '')
+            resize_decision_seq_num = int(tablet_map['_resize_decision']['sequence_number'])
+
+            tablet_transitions = {int(tablet_id['id']): transition_info
+                                  for tablet_id, transition_info in unordered_map(tablet_map['_transitions'])}
+
+            gdb.write(f'table {keyspace_name}.{table_name}: id: {table_id}, tablets: {tablet_count}, resize decision: {resize_decision}#{resize_decision_seq_num}, transitions: {len(tablet_transitions)}\n')
+
+            for tablet_id, tablet_info in enumerate(chunked_vector(tablet_map['_tablets'])):
+                last_token = self._last_token_of_compaction_group(log2_tablets, tablet_id)
+                replicas = format_replica_set(tablet_info['replicas'])
+                gdb.write(f'  tablet#{tablet_id}: last token: {last_token}, replicas: [{replicas}]\n')
+                if tablet_id in tablet_transitions:
+                    t = tablet_transitions[tablet_id]
+                    gdb.write('    transition: stage: {}, kind: {}, next: {}, pending_replica: {}, session_id: {}\n'.format(
+                        t['stage'],
+                        t['transition'],
+                        format_replica_set(t['next']),
+                        t['pending_replica'],
+                        t['session_id']))
+
+
 class scylla_gdb_func_collection_element(gdb.Function):
     """Return the element at the specified index/key from the container.
 
@@ -6270,6 +6358,7 @@ scylla_databases()
 scylla_commitlog()
 scylla_keyspaces()
 scylla_tables()
+scylla_table()
 scylla_memory()
 scylla_ptr()
 scylla_mem_ranges()
@@ -6314,6 +6403,7 @@ scylla_get_config_value()
 scylla_range_tombstones()
 scylla_sstable_promoted_index()
 scylla_sstable_dump_cached_index()
+scylla_tablet_metadata()
 
 
 # Convenience functions

test/scylla_gdb/test_misc.py

@@ -36,6 +36,9 @@ def test_tables(gdb):
 def test_table(gdb):
     scylla(gdb, 'table system.local')
 
+def test_tablet_metadata(gdb):
+    scylla(gdb, 'tablet-metadata')
+
 def test_keyspaces(gdb):
     scylla(gdb, 'keyspaces')