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https://issues.apache.org/jira/browse/CASSANDRA-3412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13207169#comment-13207169
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Peter Schuller commented on CASSANDRA-3412:
-------------------------------------------
Our internal tool (external, in python, based on describe_ring) simply uses
{{describe_ring}} and looks at each range and their responsible nodes and just
adds them all up. The ownership we report for a node is the total amount of
ringspace (regardless of primary/secondary/dc/etc concerns) that the node has,
compared to the overall total.
It ends up giving you the real number while completely blackboxing "why" we got
there - whether it be due to rack awareness (CASSANDRA-3810) or DC:s.
FWIW, here is the code for that. It's not self-contained and won't run, but
it's an FYI. The topology_xref is just post-processing the describe ring
results to yield the map of range -> nodes_responsible.
{code}
def cmd_effective_ownership(opts, args):
"""
Print effective ownership of nodes in a cluster.
Effective ownership means the actual amount of the ring for which
it has data, whether or not it is because it is the primary or
secondary (etc) owner of the ring segment. This is essentially the
ownership you would want "nodetool ring" to print but doesn't.
"""
if not args and not opts.all:
return
node_ranges, range_nodes = topology_xref(describe_ring(*((opts,) +
split_hostport(seed(opts, 'localhost') if opts.all else args[0]))))
if opts.all:
args = node_ranges.keys()
# acrobatics to handle wrap-around
max_token = 0
min_token = 2**127
for r in range_nodes.keys():
if r[0] < min_token:
min_token = r[0]
if r[1] > max_token:
max_token = r[1]
def ownership(start_token, end_token):
start_token, end_token = int(start_token), int(end_token)
if end_token < start_token:
# wrap-around
return end_token + (2**127 - start_token)
else:
return end_token - start_token
toprint = [] # list of (owned, ranges), later to be sorted
for node in (hostnames.normalize_hostname(arg) for arg in args):
if not node in node_ranges:
raise cmdline.UserError('node %s not in ring' % (node,))
ranges = node_ranges[node]
owned = reduce(lambda a, b: a + b, [ownership(r[0], r[1]) for r in
ranges], 0)
toprint.append((owned, node, ranges))
toprint = sorted(toprint, reverse=True)
for owned, node, ranges in toprint:
print '%s %f%%' % (node, float(owned) / 2**127 * 100.0)
if opts.print_ranges:
for r in sorted(ranges):
print ' %s - %s' % (r[0], r[1])
{code}
> make nodetool ring ownership smarter
> ------------------------------------
>
> Key: CASSANDRA-3412
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3412
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Jackson Chung
> Assignee: Vijay
> Priority: Minor
>
> just a thought.. the ownership info currently just look at the token and
> calculate the % between nodes. It would be nice if it could do more, such as
> discriminate nodes of each DC, replica set, etc.
> ticket is open for suggestion...
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