--- sidebar_position: 46 sidebar_label: Troubleshooting --- # Troubleshooting - [Installation](#troubleshooting-installation-errors) - [Connecting to the server](#troubleshooting-accepts-no-connections) - [Query processing](#troubleshooting-does-not-process-queries) - [Efficiency of query processing](#troubleshooting-too-slow) ## Installation {#troubleshooting-installation-errors} ### You Cannot Get Deb Packages from ClickHouse Repository with Apt-get {#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](../getting-started/install.md) article and install them manually using the `sudo dpkg -i ` command. You will also need the `tzdata` package. ## Connecting to the Server {#troubleshooting-accepts-no-connections} Possible issues: - The server is not running. - Unexpected or wrong configuration parameters. ### Server Is Not Running {#server-is-not-running} **Check if server is running** Command: ``` bash $ sudo service clickhouse-server status ``` If the server is not running, start it with the command: ``` bash $ 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: - ` Application: starting up.` — Server started. - ` Application: Ready for connections.` — Server is running and ready for connections. If `clickhouse-server` start failed with a configuration error, you should see the `` string with an error description. For example: ``` text 2019.01.11 15:23:25.549505 [ 45 ] {} 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: ``` text Application: starting up. ``` If you try to start a second instance of `clickhouse-server` on the server, you see the following log: ``` text 2019.01.11 15:25:11.151730 [ 1 ] {} : Starting ClickHouse 19.1.0 with revision 54413 2019.01.11 15:25:11.154578 [ 1 ] {} Application: starting up 2019.01.11 15:25:11.156361 [ 1 ] {} 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 ] {} Application: DB::Exception: Cannot lock file ./status. Another server instance in same directory is already running. 2019.01.11 15:25:11.156682 [ 1 ] {} Application: shutting down 2019.01.11 15:25:11.156686 [ 1 ] {} Application: Uninitializing subsystem: Logging Subsystem 2019.01.11 15:25:11.156716 [ 2 ] {} 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: ``` bash $ sudo journalctl -u clickhouse-server ``` **Start clickhouse-server in interactive mode** ``` bash $ 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 {#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](../operations/server-configuration-parameters/settings.md#server_configuration_parameters-listen_host) and [tcp_port](../operations/server-configuration-parameters/settings.md#server_configuration_parameters-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: - The [tcp_port_secure](../operations/server-configuration-parameters/settings.md#server_configuration_parameters-tcp_port_secure) setting. - Settings for [SSL certificates](../operations/server-configuration-parameters/settings.md#server_configuration_parameters-openssl). 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 {#troubleshooting-does-not-process-queries} 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: ``` bash $ 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 {#troubleshooting-too-slow} 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.