[
https://issues.apache.org/jira/browse/KAFKA-6142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16450299#comment-16450299
]
Robert Yokota edited comment on KAFKA-6142 at 4/24/18 5:59 PM:
---------------------------------------------------------------
We might also want variables to be able to refer to properties in the same file:
{{consumer.ssl.truststore.location=$\{producer.ssl.truststore.location}}}
so a different syntax might be
{code}${ env:env_var_name, sys:sys_prop_name; defaultValue }{code}
Note the use of semicolon to delimit the defaultValue. The use of env: and
sys: is the same as in Apache Commons Configuration.
was (Author: rayokota):
We might also want variables to be able to refer to properties in the same file:
{{consumer.ssl.truststore.location=${producer.ssl.truststore.location}}}
so a different syntax might be
{{${ env:env_var_name, sys:sys_prop_name; defaultValue }}}
Note the use of semicolon to delimit the defaultValue. The use of env: and
sys: is the same as in Apache Commons Configuration.
> Connect worker configurations and connector configurations should accept
> environment variables
> ----------------------------------------------------------------------------------------------
>
> Key: KAFKA-6142
> URL: https://issues.apache.org/jira/browse/KAFKA-6142
> Project: Kafka
> Issue Type: Improvement
> Components: KafkaConnect
> Affects Versions: 1.0.0
> Reporter: Randall Hauch
> Priority: Major
> Labels: needs-kip
>
> Currently, when a worker or connector configuration is parsed, the values are
> used as-is without any kind of pre-processing before the value is used. It
> should be possible to define configuration properties such that string
> literal values or default values can use *_configuration variables_* that
> reference environment variables and/or system properties, and that these
> configuration variables are resolved/replaced before the configuration value
> is used.
> I propose doing this enhancement in Kafka client's {{ConfigDef}} by adding a
> {{ConfigDef.Transformer}} interface:
> {code:java}
> /**
> * Transform the configuration value.
> */
> public interface Transformer {
> /**
> * Transform the configuration value.
> * @param name The name of the configuration
> * @param value The value of the configuration
> * @return the preprocessed value
> * @throws ConfigException if the value is invalid.
> */
> Object apply(String name, Object value);
> }
> {code}
> and then allowing {{Transformer}} implementations to be passed to
> {{ConfigDef.define(...)}} such all existing signatures are maintained for
> backward compatibility. By default, the definition would use an identity
> transform that simply returns the value. The transformers would be called in
> {{ConfigDef.parseValue(...)}} before the {{parseType(...)}} method is called,
> and would also be called on the default value if one is provided.
> Then, a {{ConfigDef.ReplaceSystemVariables}} implementation would be provided
> to look in {{String}} values for zero or more variables defined with this
> EBNF grammar:
> {noformat}
> '$' '{' varName { ',' varName } [ ':' [ defaultValue] ] '}'
> varName ::= varChar+
> defaultValue ::= varChar*
> varChar ::= any character excluding ',', ':', '}', and '\' except when escaped
> {noformat}
> where:
> * {{varName}} is the name of a Java system property or {{env.}} followed by
> the name of an environment variable, and
> * {{defaultValue}} specifies the replacement value used when no environment
> variable or system property is found, and defaults to an empty string if the
> `:` is included in the variable
> The value of the first system property or environment variable resolved is
> then used to replace the variable expression. This implementation would have
> trace or debug level logging to describe what it is doing.
> Here are several examples:
> ||Variable||Variable replaced with||
> |$\{env.KAFKA_HOME\}| the value of the {{KAFKA_HOME}} environment variable or
> a null value if that variable doesn't exist |
> |$\{foo.prop1,foo.prop2,env.MY_ENV_VAR:value\}| the value of the
> {{foo.prop1}} system property if it exists, or with the value of the
> {{foo.prop2}} system property if it exists, or with the value of the
> {{MY_ENV_VAR}} environment variable if it exists, or {{value}} if none of the
> system properties exist |
> |$\{foo.prop1,foo.prop2,env.MY_ENV_VAR:\} | the value of the {{foo.prop1}}
> system property if it exists, or with the value of the {{foo.prop2}} system
> property if it exists, or with the value of the {{MY_ENV_VAR}} environment
> variable if it exists, or an empty string if none of the system properties
> exist |
> |$\{foo.prop1,foo.prop2,env.MY_ENV_VAR\} | the value of the {{foo.prop1}}
> system property if it exists, or with the value of the {{foo.prop2}} system
> property if it exists, or with the value of the {{MY_ENV_VAR}} environment
> variable if it exists, or a null value if none of the system properties exist
> |
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
