When I queried `system.metrics` table, I found some negative values which hint to some potential internal overflows.

```
SELECT *
FROM system.metrics
FORMAT Vertical

...

Row 31:
───────
metric:      MemoryTrackingInBackgroundProcessingPool
value:       -580863171
description: Total amount of memory (bytes) allocated in background processing pool (that is dedicated for backround merges, mutations and fetches). Note that this value may include a drift when the memory was allocated in a context of background processing pool and freed in other context or vice-versa. This happens naturally due to caches for tables indexes and doesn't indicate memory leaks.

Row 32:
───────
metric:      MemoryTrackingInBackgroundMoveProcessingPool
value:       0
description: Total amount of memory (bytes) allocated in background processing pool (that is dedicated for backround moves). Note that this value may include a drift when the memory was allocated in a context of background processing pool and freed in other context or vice-versa. This happens naturally due to caches for tables indexes and doesn't indicate memory leaks.

Row 33:
───────
metric:      MemoryTrackingInBackgroundSchedulePool
value:       -4461308831
description: Total amount of memory (bytes) allocated in background schedule pool (that is dedicated for bookkeeping tasks of Replicated tables).

...

56 rows in set. Elapsed: 0.003 sec.
```

Server version: 20.8.2.3.
{
    std::lock_guard lock(shared->zookeeper_mutex);
    shared->zookeeper.reset();
}
void Context::reloadZooKeeperIfChanged(const ConfigurationPtr & config) const
{
    std::lock_guard lock(shared->zookeeper_mutex);
    if (!shared->zookeeper || shared->zookeeper->configChanged(*config, "zookeeper"))
    {
        shared->zookeeper = std::make_shared<zkutil::ZooKeeper>(*config, "zookeeper");
    }
}
bool Context::hasZooKeeper() const
{
    return getConfigRef().has("zookeeper");
}
void Context::setInterserverIOAddress(const String & host, UInt16 port)