#10138 (alexey-milovidov) It works for medium and large volumes of data (dozens of servers), but not for very large volumes of data (hundreds of servers or more). About the authors. In some cases all parts can be affected. Replicas are duplicating servers (in order to read all the data, you can access the data on any one of the replicas). When the max_parallel_replicas option is enabled, query processing is parallelized across all replicas within a single shard. 不同于replicated模式，distributed有shard的概念，即一张表的完整数据并不存放在一个物理节点上，而是分布在多个不同的物理节点。Distributed引擎本身不存储数据，不过它支持在多台server上进行分布式的，并行的查询。 Added Distributed format for File engine and file table function which allows to read from .bin files generated by asynchronous inserts into Distributed table. Data is distributed across shards in the amount proportional to the shard weight. A little bit of background on ClickHouse. A simple reminder from the division is a limited solution for sharding and isn’t always appropriate. clickhouse之distributed配置及使用 概述. Both synchronous and asynchronous mode. # docker run -it yandex/clickhouse-client --host x.x.x.12 Distributed tables will retry inserts of the same block, and those can be deduped by ClickHouse. And if your metrics suggest something is wrong—perhaps the number of rows written (clickhouse.table.insert.row.count) stays flat during an INSERT query—you can pivot to view relevant logs by clicking on a timeseries graph.Datadog is house trained. ClickHouse doesn’t delete data from the table automatically. Number of connections to remote servers sending data that was INSERTed into Distributed tables. Each cluster consists of up to ten shards with two nodes per shard for data replication. For example, you can use the expression rand() for random distribution of data, or UserID for distribution by the remainder from dividing the user’s ID (then the data of a single user will reside on a single shard, which simplifies running IN and JOIN by users). First delete the disk data, then restart the node to delete the local table, if it is a copy of the table, then go to zookeeper to delete the copy, and then rebuild the table. The Distributed engine accepts parameters: the cluster name in the server’s config file, (optionally) policy name, it will be used to store temporary files for async send. Whether to write data to just one of the replicas. As of this writing, 207 engineers have contributed to ClickHouse and the rate of commits has been accelerating for some time. Distributed tables will retry inserts of the same block, and those can be deduped by ClickHouse. You can specify a different number of replicas for each shard. Q. {replica} is the host ID macro. These companies serve an audience of 166 million Russian speakers worldwide and have some of the greatest demands for distributed OLAP systems in Europe. Second, you can perform INSERT in a Distributed table. Deduplication is performed by ClickHouse if inserting to ReplicatedMergeTree or Distributed table on top of ReplicatedMergeTree. - port – The TCP port for messenger activity (tcp_port in the config, usually set to 9000). By default, tables are created only on the current server. During a read, the table indexes on remote servers are used, if there are any. Our setup is described below then followed by clickhouse server logs that might be of interest. Do not confuse it with http_port. -->,