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Merge pull request #63813 from ClickHouse/keeper-cluster-doc
Improve documentation for from_env and from_zk
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commit
4809c39523
@ -67,6 +67,8 @@ generates merged configuration file:
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</clickhouse>
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```
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### Using from_env and from_zk
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To specify that a value of an element should be replaced by the value of an environment variable, you can use attribute `from_env`.
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Example with `$MAX_QUERY_SIZE = 150000`:
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@ -93,6 +95,59 @@ which is equal to
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</clickhouse>
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```
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The same is possible using `from_zk`:
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``` xml
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<clickhouse>
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<postgresql_port from_zk="/zk_configs/postgresql_port"/>
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</clickhouse>
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```
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```
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# clickhouse-keeper-client
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/ :) touch /zk_configs
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/ :) create /zk_configs/postgresql_port "9005"
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/ :) get /zk_configs/postgresql_port
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9005
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```
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which is equal to
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``` xml
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<clickhouse>
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<postgresql_port>9005</postgresql_port>
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</clickhouse>
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```
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#### Default values for from_env and from_zk attributes
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It's possible to set the default value and substitute it only if the environment variable or zookeeper node is set using `replace="1"`.
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With previous example, but `MAX_QUERY_SIZE` is unset:
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``` xml
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<clickhouse>
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<profiles>
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<default>
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<max_query_size from_env="MAX_QUERY_SIZE" replace="1">150000</max_query_size>
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</default>
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</profiles>
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</clickhouse>
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```
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will take the default value
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``` xml
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<clickhouse>
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<profiles>
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<default>
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<max_query_size>150000</max_query_size>
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</default>
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</profiles>
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</clickhouse>
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```
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## Substituting Configuration {#substitution}
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The config can define substitutions. There are two types of substitutions:
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