ClickHouse/docs/en/interfaces/grpc.md

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19	gRPC Protocol

gRPC Protocol

Introduction

ClickHouse supports gRPC. It is an open source remote procedure call system that uses HTTP/2 and Protocol Buffers. The implementation of gRPC protocol supports:

• SSL;
• authentication;
• sessions;
• compression;
• parallel queries through the same channel;
• cancellation of queries;
• getting progress and logs;
• external tables.

The protocol specification is described in clickhouse_grpc.proto.

ClickHouse Configuration

To use the gRPC protocol set grpc_port in the main server configuration. See the following configuration example:

<grpc_port>9100</grpc_port>
    <grpc>
        <enable_ssl>false</enable_ssl>

        <!-- The following two files are used only if enable_ssl=1 -->
        <ssl_cert_file>/path/to/ssl_cert_file</ssl_cert_file>
        <ssl_key_file>/path/to/ssl_key_file</ssl_key_file>

        <!-- Whether server will request client for a certificate -->
        <ssl_require_client_auth>false</ssl_require_client_auth>

        <!-- The following file is used only if ssl_require_client_auth=1 -->
        <ssl_ca_cert_file>/path/to/ssl_ca_cert_file</ssl_ca_cert_file>

        <!-- Default compression algorithm (applied if client doesn't specify another algorithm, see result_compression in QueryInfo).
             Supported algorithms: none, deflate, gzip, stream_gzip -->
        <compression>deflate</compression>

        <!-- Default compression level (applied if client doesn't specify another level, see result_compression in QueryInfo).
             Supported levels: none, low, medium, high -->
        <compression_level>medium</compression_level>

        <!-- Send/receive message size limits in bytes. -1 means unlimited -->
        <max_send_message_size>-1</max_send_message_size>
        <max_receive_message_size>-1</max_receive_message_size>

        <!-- Enable if you want very detailed logs -->
        <verbose_logs>false</verbose_logs>
    </grpc>

Built-in Client

You can either write a client in any of the programming languages supported by gRPC by using the provided specification or use the built-in Python client.

The built-in client is utils/grpc-client/clickhouse-grpc-client.py. It requires grpcio and grpcio-tools modules. To run the client in interactive mode call it without arguments.

Arguments:

• --help – Show this help message and exit
• --host HOST, -h HOST – The server name, ‘localhost’ by default. You can use either the name or the IPv4 or IPv6 address.
• --port PORT – The port to connect to. This port should be enabled on the ClickHouse server (see grpc_port in the config).
• --user USER_NAME, -u USER_NAME – The username. Default value: ‘default’.
• --password PASSWORD – The password. Default value: empty string.
• --query QUERY, -q QUERY – The query to process when using non-interactive mode.
• --database DATABASE, -d DATABASE – Select the current default database. Default value: the current database from the server settings (‘default’ by default).
• --format OUTPUT_FORMAT, -f OUTPUT_FORMAT – Use the specified default format to output the result.
• --debug – Enables showing the debug information.

Client Usage Example

In the following example a table is created and loaded with data from a CSV file.

./clickhouse-grpc-client.py -q "CREATE TABLE grpc_example_table (id UInt32, text String) ENGINE = MergeTree() ORDER BY id;"
echo "0,Input data for" > a.txt
echo "1,gRPC protocol example" >> a.txt
cat a.txt | ./clickhouse-grpc-client.py -q "INSERT INTO grpc_example_table FORMAT CSV"
./clickhouse-grpc-client.py --format PrettyCompact -q "SELECT * FROM grpc_example_table;"

Result:

┌─id─┬─text──────────────────┐
│  0 │ Input data for        │
│  1 │ gRPC protocol example │
└────┴───────────────────────┘