Repeated on-demand vhds updates unsubscribe from previously resolved vhosts

[dmitri-d]

Description:
If a vhost named "foo.com" has been previously resolved, an attempt to resolve "bar.com" will result in "foo.com" vhost being unsubscribed from, and all updates for it lost.

This is due to how GrpcMuxWatch::update is implemented -- it expects a list of resource names that should be watched. The resources which names are not in the list will be unsubscribed from.

edit: not an issue for NewGrpcMuxImpl::addWatch

[htuch]

@dmitri-d shouldn't we have one watch per vhost?

[dmitri-d]

@htuch: it's per subscription right now (handled by GrpcSubscriptionImpl, so the same as other xDS protocols then). I need to think about the implications of what you are suggesting. Are you thinking just VHDS, or for the rest of xDS too?

[htuch]

For RDS/EDS, there is already one subscription/watch (singleton) per consumer, e.g. each EdsClusterImpl owns a subscription for the EDS service or cluster name. These are then multiplexed in ADS to a single EDS request/response. So, in those cases, each subscribed resource has a subscription and watch.

[stale]

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