[Gluster-devel] Proposal for GlusterD-2.0

[Kaushal M]

GlusterD performs the following functions as the management daemon for
GlusterFS:
- Peer membership management
- Maintains consistency of configuration data across nodes (distributed
configuration store)
- Distributed command execution (orchestration)
- Service management (manage GlusterFS daemons)
- Portmap service for GlusterFS daemons


This proposal aims to delegate the above functions to technologies that
solve these problems well. We aim to do this in a phased manner.
The technology alternatives we would be looking for should have the
following properties,
- Open source
- Vibrant community
- Good documentation
- Easy to deploy/manage

This would allow GlusterD's architecture to be more modular. We also aim to
make GlusterD's architecture as transparent and observable as possible.
Separating out these functions would allow us to do that.

Bulk of current GlusterD code deals with keeping the configuration of the
cluster and the volumes in it consistent and available across the nodes.
The current algorithm is not scalable  (N^2 in no. of nodes) and doesn't
prevent split-brain of configuration. This is the problem area we are
targeting for the first phase.

As part of the first phase, we aim to delegate the distributed
configuration store. We are exploring consul [1] as a replacement for the
existing distributed configuration store (sum total of /var/lib/glusterd/*
across all nodes). Consul provides distributed configuration store which is
consistent and partition tolerant. By moving all Gluster related
configuration information into consul we could avoid split-brain situations.

All development efforts towards this proposal would happen in parallel to
the existing GlusterD code base. The existing code base would be actively
maintained until GlusterD-2.0 is production-ready.

This is in alignment with the GlusterFS Quattro proposals on making
GlusterFS scalable and easy to deploy. This is the first phase ground work
towards that goal.

Questions and suggestions are welcome.

~kaushal

[1] : http://www.consul.io/
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