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107 lines
4.2 KiB
Markdown
107 lines
4.2 KiB
Markdown
# Quotas {#quotas}
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Quotas allow you to limit resource usage over a period of time, or simply track the use of resources.
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Quotas are set up in the user config. This is usually 'users.xml'.
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The system also has a feature for limiting the complexity of a single query. See the section "Restrictions on query complexity").
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In contrast to query complexity restrictions, quotas:
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- Place restrictions on a set of queries that can be run over a period of time, instead of limiting a single query.
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- Account for resources spent on all remote servers for distributed query processing.
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Let's look at the section of the 'users.xml' file that defines quotas.
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```xml
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<!-- Quotas -->
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<quotas>
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<!-- Quota name. -->
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<default>
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<!-- Restrictions for a time period. You can set many intervals with different restrictions. -->
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<interval>
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<!-- Length of the interval. -->
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<duration>3600</duration>
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<!-- Unlimited. Just collect data for the specified time interval. -->
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<queries>0</queries>
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<errors>0</errors>
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<result_rows>0</result_rows>
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<read_rows>0</read_rows>
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<execution_time>0</execution_time>
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</interval>
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</default>
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```
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By default, the quota just tracks resource consumption for each hour, without limiting usage.
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The resource consumption calculated for each interval is output to the server log after each request.
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```xml
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<statbox>
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<!-- Restrictions for a time period. You can set many intervals with different restrictions. -->
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<interval>
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<!-- Length of the interval. -->
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<duration>3600</duration>
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<queries>1000</queries>
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<errors>100</errors>
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<result_rows>1000000000</result_rows>
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<read_rows>100000000000</read_rows>
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<execution_time>900</execution_time>
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</interval>
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<interval>
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<duration>86400</duration>
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<queries>10000</queries>
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<errors>1000</errors>
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<result_rows>5000000000</result_rows>
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<read_rows>500000000000</read_rows>
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<execution_time>7200</execution_time>
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</interval>
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</statbox>
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```
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For the 'statbox' quota, restrictions are set for every hour and for every 24 hours (86,400 seconds). The time interval is counted starting from an implementation-defined fixed moment in time. In other words, the 24-hour interval doesn't necessarily begin at midnight.
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When the interval ends, all collected values are cleared. For the next hour, the quota calculation starts over.
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Here are the amounts that can be restricted:
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`queries` – The total number of requests.
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`errors` – The number of queries that threw an exception.
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`result_rows` – The total number of rows given as the result.
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`read_rows` – The total number of source rows read from tables for running the query, on all remote servers.
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`execution_time` – The total query execution time, in seconds (wall time).
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If the limit is exceeded for at least one time interval, an exception is thrown with a text about which restriction was exceeded, for which interval, and when the new interval begins (when queries can be sent again).
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Quotas can use the "quota key" feature in order to report on resources for multiple keys independently. Here is an example of this:
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```xml
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<!-- For the global reports designer. -->
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<web_global>
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<!-- keyed – The quota_key "key" is passed in the query parameter,
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and the quota is tracked separately for each key value.
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For example, you can pass a Yandex.Metrica username as the key,
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so the quota will be counted separately for each username.
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Using keys makes sense only if quota_key is transmitted by the program, not by a user.
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You can also write <keyed_by_ip /> so the IP address is used as the quota key.
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(But keep in mind that users can change the IPv6 address fairly easily.)
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-->
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<keyed />
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```
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The quota is assigned to users in the 'users' section of the config. See the section "Access rights".
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For distributed query processing, the accumulated amounts are stored on the requestor server. So if the user goes to another server, the quota there will "start over".
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When the server is restarted, quotas are reset.
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[Original article](https://clickhouse.tech/docs/en/operations/quotas/) <!--hide-->
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