NIFI-12095 Increase default Xmx to 1g

[nandorsoma]

Summary

NIFI-12095

Tracking

Please complete the following tracking steps prior to pull request creation.

Issue Tracking

• Apache NiFi Jira issue created

Pull Request Tracking

• Pull Request title starts with Apache NiFi Jira issue number, such as NIFI-00000
• Pull Request commit message starts with Apache NiFi Jira issue number, as such NIFI-00000

Pull Request Formatting

• Pull Request based on current revision of the main branch
• Pull Request refers to a feature branch with one commit containing changes

Verification

Please indicate the verification steps performed prior to pull request creation.

Build

• Build completed using mvn clean install -P contrib-check
  • JDK 21

Licensing

• New dependencies are compatible with the Apache License 2.0 according to the License Policy
• New dependencies are documented in applicable LICENSE and NOTICE files

Documentation

• Documentation formatting appears as expected in rendered files

[exceptionfactory]

Thanks for proposing this change @nandorsoma. Increasing the default heap size seems reasonable. As noted in the details, the minimum heap size should be changed to match the maximum.

[exceptionfactory]

The minimum heap size should be changed to match the maximum heap size.

[nandorsoma]

Thanks for the review @exceptionfactory. Just out of curiosity, what is the reason for that? I thought a rule of thumb is to initially have the minimum as the 50% of the maximum heap size.

[exceptionfactory]

Setting the minimum heap size to the same as the maximum makes the overall process memory usage more predictable. There are other factors that contribute to total process memory usage, but heap is usually the primary contributor. Starting out with the same amount of heap as the maximum avoids unexpected surprises when the heap grows to handle cached objects.

[joewitt]

We're not trying to share with other services generally. We want the 1GB or whatever is set. But if users want the ability to let it flex they could do so. For now it is better in our applications case to just take what we want from the get go. I'm not sure it matters much in practice these days frankly.

[timeabarna]

LGTM, merging to main and support/nifi-1.x

[joewitt]

I left a comment on the JIRA. I only plan to merge to main. Don't see any reason to change the default at this point on the 1.x line.