When checking if federation is necessary, the code compares
the SRV record stored in etcd against the list of endpoints
that the MinIO server is exposing. If there is an intersection
in this list the request is forwarded.
The SRV record includes both the host and the port, but the
intersection check previously only looked at the IP address. This
would prevent federation from working in situations where the endpoint
IP is the same for multiple MinIO servers. Some examples of where this
can occur are:
- running mulitiple copies of MinIO on the same host
- using multiple MinIO servers behind a NAT with port-forwarding
Problem: MinIO incorrectly appends DNS SRV records of buckets that have a prefix match with a given bucket. E.g bucket1 would incorrectly get bucket's DNS records too.
Solution: This fix ensures that we only add SRV records that match the key exactly
common prefixes in bucket name if already created
are disallowed when etcd is configured due to the
prefix matching issue. Make sure that when we look
for bucket we are only interested in exact bucket
name not the prefix.
Currently we would end up considering common prefix
buckets to be part of the same DNS service record,
which leads to Minio server wrongly forwarding the
records to incorrect IPs.
With CoreDNS now supporting etcdv3 as the DNS backend, we
can update our federation target to etcdv3. Users will now be
able to use etcdv3 server as the federation backbone.
Minio will update bucket data to etcdv3 and CoreDNS can pick
that data up and serve it as bucket style DNS path.
