Hello,

after updating clickhouse from 21.2.3.15-2 to 21.3.2.5-2 I see those warnings :

 `<Warning> default.osb4_reverse.DirectoryMonitor: Structure does not match (remote: Path LowCardinality(String) ColumnLowCardinality(size = 0, UInt8(size = 0), ColumnUnique(size = 1, String(size = 1))), Value Float64 Float64(size = 0), Time UInt32 UInt32(size = 0), Date Date UInt16(size = 0), Timestamp UInt32 UInt32(size = 0), local: Path LowCardinality(String) ColumnLowCardinality(size = 0, UInt16(size = 0), ColumnUnique(size = 1, String(size = 1))), Value Float64 Float64(size = 0), Time UInt32 UInt32(size = 0), Date Date UInt16(size = 0), Timestamp UInt32 UInt32(size = 0)), implicit conversion will be done`

I think this is related to https://github.com/ClickHouse/ClickHouse/pull/19947

The only difference between remote and local I found inside this log is :

ColumnLowCardinality(size = 0, UInt8(size = 0) to
ColumnLowCardinality(size = 0, UInt16(size = 0)

But I don't see the difference between the tables.

```
SHOW CREATE TABLE default.osb4_reverse

CREATE TABLE default.osb4_reverse
(
    `Path` LowCardinality(String) CODEC(ZSTD(15)),
    `Value` Float64 CODEC(Gorilla, ZSTD(22)),
    `Time` UInt32 CODEC(DoubleDelta, ZSTD(15)),
    `Date` Date CODEC(Delta(2), ZSTD(22)),
    `Timestamp` UInt32 CODEC(ZSTD(15))
)
ENGINE = Distributed('osb4_hpc_metrics', '', 'osb4_reverse', rand())


CREATE TABLE osb4_metrics_r0.osb4_reverse
(
    `Path` LowCardinality(String) CODEC(ZSTD(15)),
    `Value` Float64 CODEC(Gorilla, ZSTD(22)),
    `Time` UInt32 CODEC(DoubleDelta, ZSTD(15)),
    `Date` Date CODEC(Delta(2), ZSTD(22)),
    `Timestamp` UInt32 CODEC(ZSTD(15))
)
ENGINE = ReplicatedReplacingMergeTree('/clickhouse/clusters/osb4_hpc_metrics/tables/{table4}/data', '{host2}')
PARTITION BY toYYYYMM(Date)
ORDER BY (Path, Time)
TTL Date + toIntervalMonth(6)
SETTINGS index_granularity = 8192
```

Any hints ?

Ralph
std::lock_guard metrics_lock(metrics_mutex);
                do_sleep = true;
                ++error_count;
                sleep_time = std::min(
                    std::chrono::milliseconds{Int64(default_sleep_time.count() * std::exp2(error_count))},
                    max_sleep_time);
                tryLogCurrentException(getLoggerName().data());
                last_exception = std::current_exception();
            }
        }
        else
        {
            LOG_DEBUG(log, "Skipping send data over distributed table.");
        }
        const auto now = std::chrono::system_clock::now();
        if (now - last_decrease_time > decrease_error_count_period)
        {
            std::lock_guard metrics_lock(metrics_mutex);
            error_count /= 2;
            last_decrease_time = now;
        }
        if (do_sleep)
            break;
    }
    
    getFiles();
    if (!quit && do_sleep)
        task_handle->scheduleAfter(sleep_time.count());
}
ConnectionPoolPtr StorageDistributedDirectoryMonitor::createPool(const std::string & name, const StorageDistributed & storage)