* pb: ask the master what each collection holds
Callers tracking usage were sent every volume in the cluster to add up
themselves, which is the master's largest single allocation.
* topology: summarise what each collection holds
One pass over the topology, allocating per collection rather than per volume.
Regular volumes count once each for logical totals and once per replica for
physical, taken from the lookup index, which is already keyed by volume and so
needs no set of seen ids. Ec shards are node-local so their sizes sum, while
the file and delete counts describe the volume and resolve once every holder
has been seen.
Replicas of one volume disagree while a write is landing or a heartbeat is
late. Walking a full listing took whichever replica the map iteration reached
first, so the answer moved between runs; this takes the largest, which is
stable and never reports usage below what some replica already holds.
* s3: take bucket sizes from the master's summary
The bucket size metrics pulled the whole volume list once a minute and added it
up, which cost the master 184.6MB of allocation and 17.8MB on the wire for six
numbers per collection.
VolumeList over 550k volumes 184.6 MB allocated, 17.8 MB on the wire
CollectionStatistics 176 bytes allocated, 47 bytes on the wire
The aggregation moves to the master with it, so the cases the removed tests
covered are now asserted against it directly.
* topology: count the replica holding the most live data
Quotas are enforced on size less deletions, and the replica with the biggest
raw size can be the one that has deleted the most. Counting it reported a
bucket smaller than it is and would leave one writable over its quota, which is
the opposite of what picking the largest was meant to guarantee.
* topology: cap a volume's deletions at what it holds
Live usage is read as a collection's size less its deletions, so a volume
reporting more deleted bytes than it has cancels live bytes belonging to other
volumes in the same bucket and reports it smaller than it is. Replica selection
already floored that volume's own live size at zero; the totals have to agree
with it.
see https://blog.aqwari.net/xml-schema-go/
1. go get aqwari.net/xml/cmd/xsdgen
2. Add EncodingType element for ListBucketResult in AmazonS3.xsd
3. xsdgen -o s3api_xsd_generated.go -pkg s3api AmazonS3.xsd
4. Remove empty Grantee struct in s3api_xsd_generated.go
5. Remove xmlns: sed s'/http:\/\/s3.amazonaws.com\/doc\/2006-03-01\/\ //' s3api_xsd_generated.go
Chris LuandGitHub
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