This commit introduces the new go-libp2p-gorpc streaming capabilities for
Cluster. The main aim is to work towards heavily reducing memory usage when
working with very large pinsets.
As a side-effect, it takes the chance to revampt all types for all public
methods so that pointers to static what should be static objects are not used
anymore. This should heavily reduce heap allocations and GC activity.
The main change is that state.List now returns a channel from which to read
the pins, rather than pins being all loaded into a huge slice.
Things reading pins have been all updated to iterate on the channel rather
than on the slice. The full pinset is no longer fully loaded onto memory for
things that run regularly like StateSync().
Additionally, the /allocations endpoint of the rest API no longer returns an
array of pins, but rather streams json-encoded pin objects directly. This
change has extended to the restapi client (which puts pins into a channel as
they arrive) and to ipfs-cluster-ctl.
There are still pending improvements like StatusAll() calls which should also
stream responses, and specially BlockPut calls which should stream blocks
directly into IPFS on a single call.
These are coming up in future commits.
This fixes the issue about partitions not being picked based
on the amount of freespace available in them.
It additionally removes the metrics registry and carries information directly
in the metric.
Metrics have two additional fields: Weight and Partitionable.
Informers have been updated to make use of these fields. Partitions have
weights that equals to the weight of the metrics under them.
Older cluster versions will not set these fields. Partitionable is false by
default and weight has a GetWeight() function to convert value->weight when
unset. This provides backwards compatibility for the freespace metric.
