ClickHouse/docs/en/engines/table-engines/integrations/rabbitmq.md

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---
toc_priority: 6
toc_title: RabbitMQ
---
# RabbitMQ Engine {#rabbitmq-engine}
This engine allows integrating ClickHouse with [RabbitMQ](https://www.rabbitmq.com).
RabbitMQ lets you:
- Publish or subscribe to data flows.
- Process streams as they become available.
## Creating a Table {#table_engine-rabbitmq-creating-a-table}
``` sql
CREATE TABLE [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster]
(
name1 [type1] [DEFAULT|MATERIALIZED|ALIAS expr1],
name2 [type2] [DEFAULT|MATERIALIZED|ALIAS expr2],
...
) ENGINE = RabbitMQ SETTINGS
rabbitmq_host_port = 'host:port',
rabbitmq_exchange_name = 'exchange_name',
rabbitmq_format = 'data_format'[,]
[rabbitmq_exchange_type = 'exchange_type',]
[rabbitmq_routing_key_list = 'key1,key2,...',]
[rabbitmq_row_delimiter = 'delimiter_symbol',]
[rabbitmq_num_consumers = N,]
[rabbitmq_num_queues = N,]
[rabbitmq_transactional_channel = 0]
```
Required parameters:
- `rabbitmq_host_port` host:port (for example, `localhost:5672`).
- `rabbitmq_exchange_name` RabbitMQ exchange name.
- `rabbitmq_format` Message format. Uses the same notation as the SQL `FORMAT` function, such as `JSONEachRow`. For more information, see the [Formats](../../../interfaces/formats.md) section.
Optional parameters:
- `rabbitmq_exchange_type` The type of RabbitMQ exchange: `direct`, `fanout`, `topic`, `headers`, `consistent-hash`. Default: `fanout`.
- `rabbitmq_routing_key_list` A comma-separated list of routing keys.
- `rabbitmq_row_delimiter` Delimiter character, which ends the message.
- `rabbitmq_num_consumers` The number of consumers per table. Default: `1`. Specify more consumers if the throughput of one consumer is insufficient.
- `rabbitmq_num_queues` The number of queues per consumer. Default: `1`. Specify more queues if the capacity of one queue per consumer is insufficient. Single queue can contain up to 50K messages at the same time.
- `rabbitmq_transactional_channel` Wrap insert queries in transactions. Default: `0`.
Required configuration:
The RabbitMQ server configuration should be added using the ClickHouse config file.
``` xml
<rabbitmq>
<username>root</username>
<password>clickhouse</password>
</rabbitmq>
```
Example:
``` sql
CREATE TABLE queue (
key UInt64,
value UInt64
) ENGINE = RabbitMQ SETTINGS rabbitmq_host_port = 'localhost:5672',
rabbitmq_exchange_name = 'exchange1',
rabbitmq_format = 'JSONEachRow',
rabbitmq_num_consumers = 5;
```
## Description {#description}
`SELECT` is not particularly useful for reading messages (except for debugging), because each message can be read only once. It is more practical to create real-time threads using materialized views. To do this:
1. Use the engine to create a RabbitMQ consumer and consider it a data stream.
2. Create a table with the desired structure.
3. Create a materialized view that converts data from the engine and puts it into a previously created table.
When the `MATERIALIZED VIEW` joins the engine, it starts collecting data in the background. This allows you to continually receive messages from RabbitMQ and convert them to the required format using `SELECT`.
One RabbitMQ table can have as many materialized views as you like.
Data can be channeled based on `rabbitmq_exchange_type` and the specified `rabbitmq_routing_key_list`.
There can be no more than one exchange per table. One exchange can be shared between multiple tables - it enables routing into multiple tables at the same time.
Exchange type options:
- `direct` - Routing is based on exact matching of keys. Example table key list: `key1,key2,key3,key4,key5`, message key can eqaul any of them.
- `fanout` - Routing to all tables (where exchange name is the same) regardless of the keys.
- `topic` - Routing is based on patterns with dot-separated keys. Examples: `*.logs`, `records.*.*.2020`, `*.2018,*.2019,*.2020`.
- `headers` - Routing is based on `key=value` matches with a setting `x-match=all` or `x-match=any`. Example table key list: `x-match=all,format=logs,type=report,year=2020`.
- `consistent-hash` - Data is evenly distributed between all bound tables (where exchange name is the same). Note that this exchange type must be enabled with RabbitMQ plugin: `rabbitmq-plugins enable rabbitmq_consistent_hash_exchange`.
If exchange type is not specified, then default is `fanout` and routing keys for data publishing must be randomized in range `[1, num_consumers]` for every message/batch (or in range `[1, num_consumers * num_queues]` if `rabbitmq_num_queues` is set). This table configuration works quicker then any other, especially when `rabbitmq_num_consumers` and/or `rabbitmq_num_queues` parameters are set.
If `rabbitmq_num_consumers` and/or `rabbitmq_num_queues` parameters are specified along with `rabbitmq_exchange_type`, then:
- `rabbitmq-consistent-hash-exchange` plugin must be enabled.
- `message_id` property of the published messages must be specified (unique for each message/batch).
Example:
``` sql
CREATE TABLE queue (
key UInt64,
value UInt64
) ENGINE = RabbitMQ SETTINGS rabbitmq_host_port = 'localhost:5672',
rabbitmq_exchange_name = 'exchange1',
rabbitmq_exchange_type = 'headers',
rabbitmq_routing_key_list = 'format=logs,type=report,year=2020',
rabbitmq_format = 'JSONEachRow',
rabbitmq_num_consumers = 5;
CREATE TABLE daily (key UInt64, value UInt64)
ENGINE = MergeTree();
CREATE MATERIALIZED VIEW consumer TO daily
AS SELECT key, value FROM queue;
SELECT key, value FROM daily ORDER BY key;
```