tier: Add force flag to remove a tier

[vadmeste]

Sometimes, the tier is down or its address change and we could have
many reasons why it is not possible to reach the tier server during removal
of a tier. For that, we need to add a force flag.

[harshavardhana]

what are the consequences of doing this wrong?

[vadmeste]

what are the consequences of doing this wrong?

for now, it is not possible to re-add the tier again. Currently if the tier contains some data, then the removal will not work until the user removes the data manually from the tier. However, there are some other corner cases, like the tier is down (like a user decided to kill the tiering itself). You can never remove this tier configuration in MinIO side in that case.

[harshavardhana]

for now, it is not possible to re-add the tier again. Currently if the tier contains some data, then the removal will not work until the user removes the data manually from the tier. However, there are some other corner cases, like the tier is down (like a user decided to kill the tiering itself). You can never remove this tier configuration in MinIO side in that case.

yes but this is disastrous, all the data that exists on the hot-tier will become stale and dangling.

I don't think we need this feature at all.

[vadmeste]

I don't think we need this feature at all.

Well, it is a force flag, we can require --dangerous in addition to --force in mc.

mc ilm tier remove <ALIAS> AZTIER --force --dangerous

I said there are some scenarios where you cannot remove the existing tier anymore, like a user who shutdowns the tier before removing the tier config in MinIO, the tier configuration will be stuck in MinIO forever.

[harshavardhana]

I don't think we need this feature at all.

Well, it is a force flag, we can require --dangerous in addition to --force in mc.

mc ilm tier remove <ALIAS> AZTIER --force --dangerous

I said there are some scenarios where you cannot remove the existing tier anymore, like a user who shutdowns the tier before removing the tier config in MinIO, the tier configuration will be stuck in MinIO forever.

Then we can make this a hidden feature in mc, there is no good reason user should do that.

It's a data loss scenario and it's not a daily use behavior.