# Server settings ## builtin_dictionaries_reload_interval The interval in seconds before reloading built-in dictionaries. ClickHouse reloads built-in dictionaries every x seconds. This makes it possible to edit dictionaries "on the fly" without restarting the server. Default value: 3600. **Example** ```xml 3600 ``` ## compression Data compression settings. !!! warning Don't use it if you have just started using ClickHouse. The configuration looks like this: ```xml ... ``` You can configure multiple sections ``. Block field ``: - ``min_part_size`` – The minimum size of a table part. - ``min_part_size_ratio`` – The ratio of the minimum size of a table part to the full size of the table. - ``method`` – Compression method. Acceptable values ​: ``lz4`` or ``zstd``(experimental). ClickHouse checks `min_part_size` and `min_part_size_ratio` and processes the `case` blocks that match these conditions. If none of the `` matches, ClickHouse applies the `lz4` compression algorithm. **Example** ```xml 10000000000 0.01 zstd ``` ## default_database The default database. To get a list of databases, use the [SHOW DATABASES](../../query_language/misc.md#query_language_queries_show_databases) query. **Example** ```xml default ``` ## default_profile Default settings profile. Settings profiles are located in the file specified in the parameter [user_config](#user-config). **Example** ```xml default ``` ## dictionaries_config The path to the config file for external dictionaries. Path: - Specify the absolute path or the path relative to the server config file. - The path can contain wildcards \* and ?. See also "[External dictionaries](../../query_language/dicts/external_dicts.md)". **Example** ```xml *_dictionary.xml ``` ## dictionaries_lazy_load Lazy loading of dictionaries. If `true`, then each dictionary is created on first use. If dictionary creation failed, the function that was using the dictionary throws an exception. If `false`, all dictionaries are created when the server starts, and if there is an error, the server shuts down. The default is `true`. **Example** ```xml true ``` ## format_schema_path The path to the directory with the schemes for the input data, such as schemas for the [CapnProto](../../interfaces/formats.md#format_capnproto) format. **Example** ```xml format_schemas/ ``` ## graphite Sending data to [Graphite](https://github.com/graphite-project). Settings: - host – The Graphite server. - port – The port on the Graphite server. - interval – The interval for sending, in seconds. - timeout – The timeout for sending data, in seconds. - root_path – Prefix for keys. - metrics – Sending data from a :ref:`system_tables-system.metrics` table. - events – Sending data from a :ref:`system_tables-system.events` table. - asynchronous_metrics – Sending data from a :ref:`system_tables-system.asynchronous_metrics` table. You can configure multiple `` clauses. For instance, you can use this for sending different data at different intervals. **Example** ```xml localhost 42000 0.1 60 one_min true true true ``` ## graphite_rollup Settings for thinning data for Graphite. For more details, see [GraphiteMergeTree](../../operations/table_engines/graphitemergetree.md). **Example** ```xml max 0 60 3600 300 86400 3600 ``` ## http_port/https_port The port for connecting to the server over HTTP(s). If `https_port` is specified, [openSSL](#openssl) must be configured. If `http_port` is specified, the openSSL configuration is ignored even if it is set. **Example** ```xml 0000 ``` ## http_server_default_response The page that is shown by default when you access the ClickHouse HTTP(s) server. **Example** Opens `https://tabix.io/` when accessing ` http://localhost: http_port`. ```xml
]]>
``` ## include_from The path to the file with substitutions. For more information, see the section "[Configuration files](../configuration_files.md#configuration_files)". **Example** ```xml /etc/metrica.xml ``` ## interserver_http_port Port for exchanging data between ClickHouse servers. **Example** ```xml 9009 ``` ## interserver_http_host The host name that can be used by other servers to access this server. If omitted, it is defined in the same way as the `hostname-f` command. Useful for breaking away from a specific network interface. **Example** ```xml example.yandex.ru ``` ## keep_alive_timeout The number of seconds that ClickHouse waits for incoming requests before closing the connection. Defaults to 10 seconds **Example** ```xml 10 ``` ## listen_host Restriction on hosts that requests can come from. If you want the server to answer all of them, specify `::`. Examples: ```xml ::1 127.0.0.1 ``` ## logger Logging settings. Keys: - level – Logging level. Acceptable values: ``trace``, ``debug``, ``information``, ``warning``, ``error``. - log – The log file. Contains all the entries according to `level`. - errorlog – Error log file. - size – Size of the file. Applies to ``log``and``errorlog``. Once the file reaches ``size``, ClickHouse archives and renames it, and creates a new log file in its place. - count – The number of archived log files that ClickHouse stores. **Example** ```xml trace /var/log/clickhouse-server/clickhouse-server.log /var/log/clickhouse-server/clickhouse-server.err.log 1000M 10 ``` Writing to the syslog is also supported. Config example: ```xml 1
syslog.remote:10514
myhost.local LOG_LOCAL6 syslog
``` Keys: - user_syslog — Required setting if you want to write to the syslog. - address — The host[:порт] of syslogd. If omitted, the local daemon is used. - hostname — Optional. The name of the host that logs are sent from. - facility — [The syslog facility keyword](https://en.wikipedia.org/wiki/Syslog#Facility) in uppercase letters with the "LOG_" prefix: (``LOG_USER``, ``LOG_DAEMON``, ``LOG_LOCAL3``, and so on). Default value: ``LOG_USER`` if ``address`` is specified, ``LOG_DAEMON otherwise.`` - format – Message format. Possible values: ``bsd`` and ``syslog.`` ## macros Parameter substitutions for replicated tables. Can be omitted if replicated tables are not used. For more information, see the section "[Creating replicated tables](../../operations/table_engines/replication.md)". **Example** ```xml ``` ## mark_cache_size Approximate size (in bytes) of the cache of "marks" used by [MergeTree](../../operations/table_engines/mergetree.md). The cache is shared for the server and memory is allocated as needed. The cache size must be at least 5368709120. **Example** ```xml 5368709120 ``` ## max_concurrent_queries The maximum number of simultaneously processed requests. **Example** ```xml 100 ``` ## max_connections The maximum number of inbound connections. **Example** ```xml 4096 ``` ## max_open_files The maximum number of open files. By default: `maximum`. We recommend using this option in Mac OS X, since the `getrlimit()` function returns an incorrect value. **Example** ```xml 262144 ``` ## max_table_size_to_drop Restriction on deleting tables. If the size of a [MergeTree](../../operations/table_engines/mergetree.md) table exceeds `max_table_size_to_drop` (in bytes), you can't delete it using a DROP query. If you still need to delete the table without restarting the ClickHouse server, create the `/flags/force_drop_table` file and run the DROP query. Default value: 50 GB. The value 0 means that you can delete all tables without any restrictions. **Example** ```xml 0 ``` ## merge_tree Fine tuning for tables in the [ MergeTree](../../operations/table_engines/mergetree.md). For more information, see the MergeTreeSettings.h header file. **Example** ```xml 5 ``` ## openSSL SSL client/server configuration. Support for SSL is provided by the `libpoco` library. The interface is described in the file [SSLManager.h](https://github.com/ClickHouse-Extras/poco/blob/master/NetSSL_OpenSSL/include/Poco/Net/SSLManager.h) Keys for server/client settings: - privateKeyFile – The path to the file with the secret key of the PEM certificate. The file may contain a key and certificate at the same time. - certificateFile – The path to the client/server certificate file in PEM format. You can omit it if `privateKeyFile` contains the certificate. - caConfig – The path to the file or directory that contains trusted root certificates. - verificationMode – The method for checking the node's certificates. Details are in the description of the [Context](https://github.com/ClickHouse-Extras/poco/blob/master/NetSSL_OpenSSL/include/Poco/Net/Context.h) class. Possible values: ``none``, ``relaxed``, ``strict``, ``once``. - verificationDepth – The maximum length of the verification chain. Verification will fail if the certificate chain length exceeds the set value. - loadDefaultCAFile – Indicates that built-in CA certificates for OpenSSL will be used. Acceptable values: `true`, `false`. | - cipherList – Supported OpenSSL encryptions. For example: `ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH`. - cacheSessions – Enables or disables caching sessions. Must be used in combination with ``sessionIdContext``. Acceptable values: `true`, `false`. - sessionIdContext – A unique set of random characters that the server appends to each generated identifier. The length of the string must not exceed ``SSL_MAX_SSL_SESSION_ID_LENGTH``. This parameter is always recommended, since it helps avoid problems both if the server caches the session and if the client requested caching. Default value: ``${application.name}``. - sessionCacheSize – The maximum number of sessions that the server caches. Default value: 1024\*20. 0 – Unlimited sessions. - sessionTimeout – Time for caching the session on the server. - extendedVerification – Automatically extended verification of certificates after the session ends. Acceptable values: `true`, `false`. - requireTLSv1 – Require a TLSv1 connection. Acceptable values: `true`, `false`. - requireTLSv1_1 – Require a TLSv1.1 connection. Acceptable values: `true`, `false`. - requireTLSv1 – Require a TLSv1.2 connection. Acceptable values: `true`, `false`. - fips – Activates OpenSSL FIPS mode. Supported if the library's OpenSSL version supports FIPS. - privateKeyPassphraseHandler – Class (PrivateKeyPassphraseHandler subclass) that requests the passphrase for accessing the private key. For example: ````, ``KeyFileHandler``, ``test``, ````. - invalidCertificateHandler – Class (subclass of CertificateHandler) for verifying invalid certificates. For example: `` ConsoleCertificateHandler `` . - disableProtocols – Protocols that are not allowed to use. - preferServerCiphers – Preferred server ciphers on the client. **Example of settings:** ```xml /etc/clickhouse-server/server.crt /etc/clickhouse-server/server.key /etc/clickhouse-server/dhparam.pem none true true sslv2,sslv3 true true true sslv2,sslv3 true RejectCertificateHandler ``` ## part_log Logging events that are associated with [MergeTree](../../operations/table_engines/mergetree.md). For instance, adding or merging data. You can use the log to simulate merge algorithms and compare their characteristics. You can visualize the merge process. Queries are logged in the ClickHouse table, not in a separate file. Columns in the log: - event_time – Date of the event. - duration_ms – Duration of the event. - event_type – Type of event. 1 – new data part; 2 – merge result; 3 – data part downloaded from replica; 4 – data part deleted. - database_name – The name of the database. - table_name – Name of the table. - part_name – Name of the data part. - size_in_bytes – Size of the data part in bytes. - merged_from – An array of names of data parts that make up the merge (also used when downloading a merged part). - merge_time_ms – Time spent on the merge. Use the following parameters to configure logging: - database – Name of the database. - table – Name of the table. - partition_by – Sets a [custom partitioning key](../../operations/table_engines/custom_partitioning_key.md). - flush_interval_milliseconds – Interval for flushing data from memory to the disk. **Example** ```xml system part_log
toMonday(event_date) 7500
``` ## path The path to the directory containing data. !!! note The trailing slash is mandatory. **Example** ```xml /var/lib/clickhouse/ ``` ## query_log Setting for logging queries received with the [log_queries=1](../settings/settings.md) setting. Queries are logged in the ClickHouse table, not in a separate file. Use the following parameters to configure logging: - database – Name of the database. - table – Name of the table. - partition_by – Sets a [custom partitioning key](../../operations/table_engines/custom_partitioning_key.md). - flush_interval_milliseconds – Interval for flushing data from memory to the disk. If the table doesn't exist, ClickHouse will create it. If the structure of the query log changed when the ClickHouse server was updated, the table with the old structure is renamed, and a new table is created automatically. **Example** ```xml system query_log
toMonday(event_date) 7500
``` ## remote_servers Configuration of clusters used by the Distributed table engine. For more information, see the section "[Table engines/Distributed](../../operations/table_engines/distributed.md)". **Example** ```xml ``` For the value of the `incl` attribute, see the section "[Configuration files](../configuration_files.md#configuration_files)". ## timezone The server's time zone. Specified as an IANA identifier for the UTC time zone or geographic location (for example, Africa/Abidjan). The time zone is necessary for conversions between String and DateTime formats when DateTime fields are output to text format (printed on the screen or in a file), and when getting DateTime from a string. In addition, the time zone is used in functions that work with the time and date if they didn't receive the time zone in the input parameters. **Example** ```xml Europe/Moscow ``` ## tcp_port Port for communicating with clients over the TCP protocol. **Example** ```xml 9000 ``` ## tmp_path Path to temporary data for processing large queries. !!! note The trailing slash is mandatory. **Example** ```xml /var/lib/clickhouse/tmp/ ``` ## uncompressed_cache_size Cache size (in bytes) for uncompressed data used by table engines from the [MergeTree](../../operations/table_engines/mergetree.md). There is one shared cache for the server. Memory is allocated on demand. The cache is used if the option [use_uncompressed_cache](../settings/settings.md) is enabled. The uncompressed cache is advantageous for very short queries in individual cases. **Example** ```xml 8589934592 ``` ## user_files_path The directory with user files. Used in the table function [file()](../../query_language/table_functions/file.md). **Example** ```xml /var/lib/clickhouse/user_files/ ``` ## users_config Path to the file that contains: - User configurations. - Access rights. - Settings profiles. - Quota settings. **Example** ```xml users.xml ``` ## zookeeper Configuration of ZooKeeper servers. ClickHouse uses ZooKeeper for storing replica metadata when using replicated tables. This parameter can be omitted if replicated tables are not used. For more information, see the section "[Replication](../../operations/table_engines/replication.md)". **Example** ```xml ``` [Original article](https://clickhouse.yandex/docs/en/operations/server_settings/settings/)