gRPC Interface

Introduction

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

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

The specification of the interface is described in clickhouse_grpc.proto.

gRPC Configuration

To use the gRPC interface set grpc_port in the main server configuration. Other configuration options see in the following example:

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

        <!-- The following two files are used only if SSL is enabled -->
        <ssl_cert_file>/path/to/ssl_cert_file</ssl_cert_file>
        <ssl_key_file>/path/to/ssl_key_file</ssl_key_file>

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

        <!-- The following file is used only if ssl_require_client_auth=true -->
        <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 to get detailed logs -->
        <verbose_logs>false</verbose_logs>
    </grpc>

Built-in Client

You can write a client in any of the programming languages supported by gRPC using the provided specification. Or you can use a built-in Python client. It is placed in utils/grpc-client/clickhouse-grpc-client.py in the repository. The built-in client requires grpcio and grpcio-tools Python modules.

The client supports the following arguments:

• --help – Shows a help message and exits.
• --host HOST, -h HOST – A server name. Default value: localhost. You can use IPv4 or IPv6 addresses also.
• --port PORT – A port to connect to. This port should be enabled in the ClickHouse server configuration (see grpc_port). Default value: 9100.
• --user USER_NAME, -u USER_NAME – A user name. Default value: default.
• --password PASSWORD – A password. Default value: empty string.
• --query QUERY, -q QUERY – A query to process when using non-interactive mode.
• --database DATABASE, -d DATABASE – A default database. If not specified, the current database set in the server settings is used (default by default).
• --format OUTPUT_FORMAT, -f OUTPUT_FORMAT – A result output format. Default value for interactive mode: PrettyCompact.
• --debug – Enables showing debug information.

To run the client in an interactive mode call it without --query argument.

In a batch mode query data can be passed via stdin.

Client Usage Example

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

./clickhouse-grpc-client.py -q "CREATE TABLE grpc_example_table (id UInt32, text String) ENGINE = MergeTree() ORDER BY id;"
echo -e "0,Input data for\n1,gRPC protocol example" > a.csv
cat a.csv | ./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 │
└────┴───────────────────────┘