fix(server/objects): solves database connection resource leak when client connections are prematurely closed

[iainsproat]

Description & motivation

This PR fixes a long existing bug with prematurely closed streaming connections. Prior to this PR, for the /api/getobjects/* REST endpoint, if the client prematurely closed a connection to the server it was not propogated to the database connection. This resulted in the database connection never being closed, and inevitably saturation for the server and the inability to serve further traffic (reffectively a Denial of Service until the server is restarted).

The bug is due to an issue with Node.js stream.pipeline implementation, described in the documentation as so:

stream.pipeline() leaves dangling event listeners on the streams after the callback has been invoked. In the case of reuse of streams after failure, this can cause event listener leaks and swallowed errors.

Changes:

• introduces a feature flag around the fix
• introduces stream-chain library to resolve a known issue with Node.js built-in stream.pipeline
• includes a test to prevent regressions

To-do before merge:

• Fix this issue.
• Amend the test expectations to prevent regression.

Screenshots:

Before (recreating the issue):

After (the fix has been applied):

• no errors, the logs are nice and quiet. The premature close of the stream does not seem to be considered an error case.

Validation of changes:

• the included test fails if the Feature flag is disabled, and passes if the feature flag is enabled

Run the test with yarn test --run 'modules/core/tests/integration/objectsStream.rest.spec.ts' -f 'should close database connections if client connection is prematurely closed'

Checklist:

• My pull request follows the guidelines in the Contributing guide?
• My pull request does not duplicate any other open Pull Requests for the same update/change?
• My commits are related to the pull request and do not amend unrelated code or documentation.
• My code follows a similar style to existing code.
• I have added appropriate tests.
• I have updated or added relevant documentation.

References

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