Add destination cluster info to response cookie

[harishnelakurthi]

Description

Add destination cluster a query is routed to in the cookie. More details here of the use-case here: #465

Additional context and related issues

#465

Release notes

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* The cookie data for requests to `/v1/statement` API would include the cluster to which a query got routed named as `trinoClusterHost`.

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[cla-bot]

Thank you for your pull request and welcome to the Trino community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. Continue to work with us on the review and improvements in this PR, and submit the signed CLA to [email protected]. Photos, scans, or digitally-signed PDF files are all suitable. Processing may take a few days. The CLA needs to be on file before we merge your changes. For more information, see https://github.com/trinodb/cla

[cla-bot]

Thank you for your pull request and welcome to the Trino community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. Continue to work with us on the review and improvements in this PR, and submit the signed CLA to [email protected]. Photos, scans, or digitally-signed PDF files are all suitable. Processing may take a few days. The CLA needs to be on file before we merge your changes. For more information, see https://github.com/trinodb/cla

[willmostly]

I think a Cookie would be more appropriate than adding a new header. Typically headers implement the protocol, and cookies are used for storing session information and passing data back and forth

[cla-bot]

Thank you for your pull request and welcome to the Trino community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. Continue to work with us on the review and improvements in this PR, and submit the signed CLA to [email protected]. Photos, scans, or digitally-signed PDF files are all suitable. Processing may take a few days. The CLA needs to be on file before we merge your changes. For more information, see https://github.com/trinodb/cla

[willmostly]

@harishnelakurthi please sign the CLA so that we can take this forward, and address all comments. Please squash your commits as well.

[harishnelakurthi]

@willmostly - I have signed the CLA and emailed a week ago. Also, I've addressed all the comments on the PR except there was an open question which I have responded to the reviewer. Let me know if anything is needed from my end.

[willmostly]

@harishnelakurthi I think you may have missed my comment above. I would like to avoid adding a new header just to pass back information unrelated to the routing protocol. This should be a cookie. You can also update the logic such that the cookie is only added/updated in the response to a POST to v1/statement. Please update the PR title and description to reflect the change as well.

[cla-bot]

Thank you for your pull request and welcome to the Trino community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. Continue to work with us on the review and improvements in this PR, and submit the signed CLA to [email protected]. Photos, scans, or digitally-signed PDF files are all suitable. Processing may take a few days. The CLA needs to be on file before we merge your changes. For more information, see https://github.com/trinodb/cla

[harishnelakurthi]

Thanks, @willmostly I have made the changes to pass this data via session cookie. Please review and let me know if any changes are needed. Also, updated the PR title and description. Will squash the commits before merge.

[andythsu]

Can we change the PR name and commit title to "cluster" instead of "backend"

[willmostly]

@harishnelakurthi you can use Airlift's codestyle in your IDE to avoid builds failing due to checkstyle https://github.com/airlift/codestyle

[willmostly]

Looks pretty close % comments.

Can you add a test for this functionality? TestGatewayHaMultipleBackend should have the infrastructure you need