SSR: avoid sending new response when headers were already sent

[danielcoelhocgu]

References

Fixes #2315

Description

This PR solves a problem that resulted in the following warning message in logs:

Warning [ERR_HTTP_HEADERS_SENT]: Tried to set headers after they were sent to the client Error: Cannot set headers after they are sent to the client

This seems to happen when frontend redirects a request. For example when accessing a permanent URI (/handle/XXX/YYY). Although redirect works in most cases, in our particular infrastructure on AWS it causes an error message to be displayed to the user.

Instructions for Reviewers

I added a check in SSR main render function in order to avoid sending more content when HTTP headers were already sent in the same request.

To test it, make sure SSR is active and access a collection or item page using a permanent URI. Verify the logs to see if the warning message is present or not.

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[tdonohue]

👍 Thanks @danielcoelhocgu ! I see this small fix has had a lot of positive feedback in #2315. I gave it a try myself as well, and it seems to reduce the number of warnings (with no obvious side effects). I'll merge this immediately and attempt to auto-backport to 7.x, 8.x and 9.x

[dspace-bot]

Backport failed for dspace-7_x, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin dspace-7_x
git worktree add -d .worktree/backport-4733-to-dspace-7_x origin/dspace-7_x
cd .worktree/backport-4733-to-dspace-7_x
git switch --create backport-4733-to-dspace-7_x
git cherry-pick -x 951c5f69d46db57efb5423c4581b4c895793c6dd

[dspace-bot]

Successfully created backport PR for dspace-8_x:

• [Port dspace-8_x] SSR: avoid sending new response when headers were already sent #4743

[dspace-bot]

Successfully created backport PR for dspace-9_x:

• [Port dspace-9_x] SSR: avoid sending new response when headers were already sent #4744

[tdonohue]

UPDATE: This could not be automatically backported to 7.6.x, as the code in server.ts is quite different in that release. Therefore, it will require a volunteer to create a manual backport PR against the dspace-7_x branch.

However, this has been backported automatically to 8.x and 9.x and will be fixed in the next maintenance releases for those versions.