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Troubleshooting

Installation​

You Cannot Get Deb Packages from ClickHouse Repository with Apt-get​

  • Check firewall settings.
  • If you cannot access the repository for any reason, download packages as described in the install guide article and install them manually using the sudo dpkg -i <packages> command. You will also need the tzdata package.

Connecting to the Server​

Possible issues:

  • The server is not running.
  • Unexpected or wrong configuration parameters.

Server Is Not Running​

Check if server is runnnig

Command:

$ sudo service clickhouse-server status

If the server is not running, start it with the command:

$ sudo service clickhouse-server start

Check logs

The main log of clickhouse-server is in /var/log/clickhouse-server/clickhouse-server.log by default.

If the server started successfully, you should see the strings:

  • <Information> Application: starting up. β€” Server started.
  • <Information> Application: Ready for connections. β€” Server is running and ready for connections.

If clickhouse-server start failed with a configuration error, you should see the <Error> string with an error description. For example:

2019.01.11 15:23:25.549505 [ 45 ] {} <Error> ExternalDictionaries: Failed reloading 'event2id' external dictionary: Poco::Exception. Code: 1000, e.code() = 111, e.displayText() = Connection refused, e.what() = Connection refused

If you do not see an error at the end of the file, look through the entire file starting from the string:

<Information> Application: starting up.

If you try to start a second instance of clickhouse-server on the server, you see the following log:

2019.01.11 15:25:11.151730 [ 1 ] {} <Information> : Starting ClickHouse 19.1.0 with revision 54413
2019.01.11 15:25:11.154578 [ 1 ] {} <Information> Application: starting up
2019.01.11 15:25:11.156361 [ 1 ] {} <Information> StatusFile: Status file ./status already exists - unclean restart. Contents:
PID: 8510
Started at: 2019-01-11 15:24:23
Revision: 54413

2019.01.11 15:25:11.156673 [ 1 ] {} <Error> Application: DB::Exception: Cannot lock file ./status. Another server instance in same directory is already running.
2019.01.11 15:25:11.156682 [ 1 ] {} <Information> Application: shutting down
2019.01.11 15:25:11.156686 [ 1 ] {} <Debug> Application: Uninitializing subsystem: Logging Subsystem
2019.01.11 15:25:11.156716 [ 2 ] {} <Information> BaseDaemon: Stop SignalListener thread

See system.d logs

If you do not find any useful information in clickhouse-server logs or there aren’t any logs, you can view system.d logs using the command:

$ sudo journalctl -u clickhouse-server

Start clickhouse-server in interactive mode

$ sudo -u clickhouse /usr/bin/clickhouse-server --config-file /etc/clickhouse-server/config.xml

This command starts the server as an interactive app with standard parameters of the autostart script. In this mode clickhouse-server prints all the event messages in the console.

Configuration Parameters​

Check:

  • Docker settings.

    If you run ClickHouse in Docker in an IPv6 network, make sure that network=host is set.

  • Endpoint settings.

    Check listen_host and tcp_port settings.

    ClickHouse server accepts localhost connections only by default.

  • HTTP protocol settings.

    Check protocol settings for the HTTP API.

  • Secure connection settings.

    Check:

    Use proper parameters while connecting. For example, use the port_secure parameter with clickhouse_client.

  • User settings.

    You might be using the wrong user name or password.

Query Processing​

If ClickHouse is not able to process the query, it sends an error description to the client. In the clickhouse-client you get a description of the error in the console. If you are using the HTTP interface, ClickHouse sends the error description in the response body. For example:

$ curl 'http://localhost:8123/' --data-binary "SELECT a"
Code: 47, e.displayText() = DB::Exception: Unknown identifier: a. Note that there are no tables (FROM clause) in your query, context: required_names: 'a' source_tables: table_aliases: private_aliases: column_aliases: public_columns: 'a' masked_columns: array_join_columns: source_columns: , e.what() = DB::Exception

If you start clickhouse-client with the stack-trace parameter, ClickHouse returns the server stack trace with the description of an error.

You might see a message about a broken connection. In this case, you can repeat the query. If the connection breaks every time you perform the query, check the server logs for errors.

Efficiency of Query Processing​

If you see that ClickHouse is working too slowly, you need to profile the load on the server resources and network for your queries.

You can use the clickhouse-benchmark utility to profile queries. It shows the number of queries processed per second, the number of rows processed per second, and percentiles of query processing times.