NIFI-12411: Update PublishAMQP to read AMQP headers value from FlowFile attributes and amq$headers string

[umarhussain15]

Summary

NIFI-12411

Processor can now also create message headers using attributes matching the given Regex property. The name of the attribute is used as header key. In addition to that it can read values from two sources i.e. attributes matching Regex and the headers present in amq$headers string. In case of key duplication in both sources, the precedence property decide which value will be used.

AMQP attributes keys are now set as constants strings and reused where needed.

Added onScheduled to PublishAMQP and ConsumeAMQP to read all properties which don't change during running state.

Test cases added for PublishAMQP headers source changes.

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  • JDK 21

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[exceptionfactory]

Thanks for the proposed improvement @umarhussain15.

The general focus on the change makes sense, but there are some other stylistic recommendations I noted. It is helpful to improve the overall Processor implementation through the definition and reuse of static values for things like FlowFile attributes, so thanks for including those changes.

[joewitt]

@umarhussain15 Can you please rebase and consider the feedback shared from @exceptionfactory ?

Thanks

[umarhussain15]

Hi @joewitt @exceptionfactory,
I have reverted the changes of making class level variables based on processor properties.
Also, the branch is rebased on latest changes from main

[umarhussain15]

Changes applied in new commits

[umarhussain15]

@exceptionfactory @joewitt

I have added one more change, which will allow users to set amqp processor's password via env variables.
I think this will be helpful in cases where we use AMQP processors in multiple NiFI instances. Instead of copying and pasting different passwords in processor properties, we can reference the env variable via its name.
Let me know your thoughts on it.
Thanks.

[exceptionfactory]

@exceptionfactory @joewitt

I have added one more change, which will allow users to set amqp processor's password via env variables. I think this will be helpful in cases where we use AMQP processors in multiple NiFI instances. Instead of copying and pasting different passwords in processor properties, we can reference the env variable via its name. Let me know your thoughts on it. Thanks.

Thanks for calling out this particular change @umarhussain15. Given the scope of the current pull request, I recommend considering that change separately.

In general, sensitive properties such as passwords do not support reading from environment variables. The reason is that environment variables are also accessible through Expression Language, so they are not necessarily secure. The use case is still supported through Parameter Contexts and Parameter Providers, where the Environment Variable Parameter Provider can be used. This is an additional layer of indirection, but it follows the general convention for other sensitive properties.

[umarhussain15]

Thanks for the explanation, @exceptionfactory. I will revert the change here then.

[umarhussain15]

Reverted the AbstractAMQPProcessor change to support expression language in password field.

[exceptionfactory]

Thanks for following up @umarhussain15. Please note, the Checkstyle rules were recently updated to include consistency checking for whitespace, so the latest static analysis build noted these issues:

Warning:  src/main/java/org/apache/nifi/amqp/processors/PublishAMQP.java:[115,38] (whitespace) WhitespaceAfter: ',' is not followed by whitespace.
Warning:  src/main/java/org/apache/nifi/amqp/processors/PublishAMQP.java:[307,76] (whitespace) WhitespaceAfter: ',' is not followed by whitespace.
Warning:  src/main/java/org/apache/nifi/amqp/processors/PublishAMQP.java:[314,76] (whitespace) WhitespaceAfter: ',' is not followed by whitespace.
Warning:  src/main/java/org/apache/nifi/amqp/processors/PublishAMQP.java:[316,76] (whitespace) WhitespaceAfter: ',' is not followed by whitespace.
Warning:  src/main/java/org/apache/nifi/amqp/processors/PublishAMQP.java:[380,68] (whitespace) WhitespaceAround: '{' is not preceded with whitespace.
Warning:  src/main/java/org/apache/nifi/amqp/processors/ConsumeAMQP.java:[349,69] (whitespace) WhitespaceAround: '{' is not preceded with whitespace.

[umarhussain15]

Checkstyle reported issues fixed