Mike Perez wrote:
On Fri, Jul 31, 2015 at 8:56 AM, Joshua Harlow<harlo...@outlook.com> wrote:
...random thought here, skip as needed... in all honesty orchestration
solutions like mesos
(http://mesos.apache.org/assets/img/documentation/architecture3.jpg),
map-reduce solutions like hadoop, stream processing systems like apache
storm (...), are already using zookeeper and I'm not saying we should just
use it cause they are, but the likelihood that they just picked it for no
reason are imho slim.
I'd really like to see focus cross project. I don't want Ceilometer to
depend on Zoo Keeper, Cinder to depend on etcd, etc. This is not ideal
for an operator to have to deploy, learn and maintain each of these
solutions.
I think this is difficult when you consider everyone wants options of
their preferred DLM. If we went this route, we should pick one.
+1
Regardless, I want to know if we really need a DLM. Does Ceilometer
really need a DLM? Does Cinder really need a DLM? Can we just use a
hash ring solution where operators don't even have to know or care
about deploying a DLM and running multiple instances of Cinder manager
just works?
All very good questions, although IMHO a hash-ring is just a piece of
the puzzle, and is more equivalent to sharding resources, which yes is
one way to scale as long as each shard never touches anything from the
other shards. If those shards ever start to need to touch anything
shared then u get back into this same situation again for a DLM (and at
that point u really do need the 'distributed' part of DLM, because each
shard is distributed).
And an few (maybe obvious) questions:
- How would re-sharding work?
- If sharding (the hash-ring partitioning) is based on entities
(conductors/other) owning a 'bucket' of resources (ie entity 1 manages
resources A-F, entity 2 manages resources G-M...), what happens if a
entity dies, does some other entity take over that bucket, what happens
if that entity really hasn't 'died' but is just disconnected from the
network (partition tolerance...)? (If the answer is there is a lock on
the resource/s being used by each entity, then u get back into the LM
question).
I'm unsure about how ironic handles these problems (although I believe
they have a hash-ring and still have a locking scheme as well, so maybe
thats there answer for the dual-entities manipulating the same bucket
problem).
--
Mike Perez
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