Max,
What if user simply don't have configured monitoring system?
Knowing whether cluster will survive node shutdown is critical for any
administrator that performs any manipulations with cluster topology.
Essential information should be easily accessed. We shouldn't force
users to configure external tools and write extra code for basic things.
Alex,
Thanks, that's exact metric we need.
My point is that we should make it more accessible: via control.sh
command and single method for the whole cluster.
Best Regards,
Ivan Rakov
On 04.10.2019 16:34, Alex Plehanov wrote:
Ivan, there already exist metric
CacheGroupMetricsMXBean#getMinimumNumberOfPartitionCopies, which shows the
current redundancy level for the cache group.
We can lose up to ( getMinimumNumberOfPartitionCopies-1) nodes without data
loss in this cache group.
пт, 4 окт. 2019 г. в 16:17, Ivan Rakov <ivan.glu...@gmail.com>:
Igniters,
I've seen numerous requests to find out an easy way to check whether is
it safe to turn off cluster node. As we know, in Ignite protection from
sudden node shutdown is implemented through keeping several backup
copies of each partition. However, this guarantee can be weakened for a
while in case cluster has recently experienced node restart and
rebalancing process is still in progress.
Example scenario is restarting nodes one by one in order to update a
local configuration parameter. User restarts one node and rebalancing
starts: when it will be completed, it will be safe to proceed (backup
count=1). However, there's no transparent way to determine whether
rebalancing is over.
From my perspective, it would be very helpful to:
1) Add information about rebalancing and number of free-to-go nodes to
./control.sh --state command.
Examples of output:
Cluster ID: 125a6dce-74b1-4ee7-a453-c58f23f1f8fc
Cluster tag: new_tag
--------------------------------------------------------------------------------
Cluster is active
All partitions are up-to-date.
3 node(s) can safely leave the cluster without partition loss.
Cluster ID: 125a6dce-74b1-4ee7-a453-c58f23f1f8fc
Cluster tag: new_tag
--------------------------------------------------------------------------------
Cluster is active
Rebalancing is in progress.
1 node(s) can safely leave the cluster without partition loss.
2) Provide the same information via ClusterMetrics. For example:
ClusterMetrics#isRebalanceInProgress // boolean
ClusterMetrics#getSafeToLeaveNodesCount // int
Here I need to mention that this information can be calculated from
existing rebalance metrics (see CacheMetrics#*rebalance*). However, I
still think that we need more simple and understandable flag whether
cluster is in danger of data loss. Another point is that current metrics
are bound to specific cache, which makes this information even harder to
analyze.
Thoughts?
--
Best Regards,
Ivan Rakov
