Do not open dispatchers in follower role

[deepthidevaki]

Description

In follower role, StreamProcessor is running only in replay mode. When the writer is created, dispatcher is also opened which allocates direct buffer. This is unnecessary as the writer is never used. The allocated buffer consumes memory and can create memory pressure on the system. To fix this, we create the writer only after the replay is completed.

Related issues

related #8509

Definition of Done

Not all items need to be done depending on the issue and the pull request.

Code changes:

• The changes are backwards compatibility with previous versions
• If it fixes a bug then PRs are created to backport the fix to the last two minor versions. You can trigger a backport by assigning labels (e.g. backport stable/1.3) to the PR, in case that fails you need to create backports manually.

Testing:

• There are unit/integration tests that verify all acceptance criterias of the issue
• New tests are written to ensure backwards compatibility with further versions
• The behavior is tested manually
• The change has been verified by a QA run
• The impact of the changes is verified by a benchmark

Documentation:

• The documentation is updated (e.g. BPMN reference, configuration, examples, get-started guides, etc.)
• New content is added to the release announcement
• If the PR changes how BPMN processes are validated (e.g. support new BPMN element) then the Camunda modeling team should be informed to adjust the BPMN linting.

Please refer to our review guidelines.

[deepthidevaki]

Result of the benchmark : #8509 (comment)

I have also started a new benchmark with the version on this pr.

[Zelldon]

@deepthidevaki I think it makes sense to run this test on the long running benchmark, here we see more the OOM.

[deepthidevaki]

I think it makes sense to run this test on the long running benchmark, here we see more the OOM.

Yes. I will start a long running benchmark after the PR is merged.

[Zelldon]

Thanks @deepthidevaki 🚀👍

[deepthidevaki]

bors merge

[zeebe-bors-camunda]

Build succeeded:

• Smoke tests on windows-latest
• continuous-integration/jenkins/branch
• Smoke tests on macos-latest
• Smoke tests on ubuntu-latest

[lenaschoenburg]

Maybe worth to backport it to at least 8.0?

[deepthidevaki]

/backport

[github-actions]

Backport failed for stable/1.3, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin stable/1.3
git worktree add -d .worktree/backport-9367-to-stable/1.3 origin/stable/1.3
cd .worktree/backport-9367-to-stable/1.3
git checkout -b backport-9367-to-stable/1.3
ancref=$(git merge-base fc991eb19245bcae8d5a883d74c070035ee953c2 4b93b005f66e36d0ae901c8226d1446127e90bef)
git cherry-pick -x $ancref..4b93b005f66e36d0ae901c8226d1446127e90bef

[github-actions]

Backport failed for stable/8.0, because it was unable to create a new branch.

Please cherry-pick the changes locally.

git fetch origin stable/8.0
git worktree add -d .worktree/backport-9367-to-stable/8.0 origin/stable/8.0
cd .worktree/backport-9367-to-stable/8.0
git checkout -b backport-9367-to-stable/8.0
ancref=$(git merge-base fc991eb19245bcae8d5a883d74c070035ee953c2 4b93b005f66e36d0ae901c8226d1446127e90bef)
git cherry-pick -x $ancref..4b93b005f66e36d0ae901c8226d1446127e90bef