Hi Joshua,
Okay, that string appears to be a base64-encoded version 4 UUID. Why not use
Cassandra's UUID data type to store that directly rather than storing the
longer base64 string as text? --> It's an old application and the person who
coded it, has left the company.What does the UUID represent? --> Unique account
id.Is it identifying a unique product, an image, or some other type of object?
--> yesWhen and how is the underlying UUID being generated by the application?
--> Not sure about it.
I assume you're using the default partitioner, but just in case, can you
confirm which partitioner you're using in your cassandra.yaml file (e.g.
Murmer3, Random, ByteOrdered)? --> partitioner:
org.apache.cassandra.dht.Murmur3Partitioner
Mentioned Jiras are from much older version than ours "3.11.2"; Also, our
partition keys are not distributed evenly as I had pasted output earlier. Which
means none of the Jiras apply in our case :(
On Wednesday, June 20, 2018, 12:18:28 PM EDT, Joshua Galbraith
<[email protected]> wrote:
Okay, that string appears to be a base64-encoded version 4 UUID. Why not use
Cassandra's UUID data type to store that directly rather than storing the
longer base64 string as text? What does the UUID represent? Is it identifying a
unique product, an image, or some other type of object? When and how is the
underlying UUID being generated by the application?
I assume you're using the default partitioner, but just in case, can you
confirm which partitioner you're using in your cassandra.yaml file (e.g.
Murmer3, Random, ByteOrdered)?
Also, please have a look at these two issues and verify you're not experiencing
either:
* https://issues.apache.org/jira/browse/CASSANDRA-7032
* https://issues.apache.org/jira/browse/CASSANDRA-10430
On Wed, Jun 20, 2018 at 9:59 AM, learner dba <[email protected]>
wrote:
Partition key has value as:
MWY4MmI0MTQtYTk2YS00YmRjLTkxND MtOWU0MjM1OWU2NzUy other column is blob.
On Tuesday, June 19, 2018, 6:07:59 PM EDT, Joshua Galbraith
<[email protected]. INVALID> wrote:
> id text PRIMARY KEY
What values are written to this id field? Can you give us some examples or
explain the general use case?
On Tue, Jun 19, 2018 at 1:18 PM, learner dba <[email protected]. invalid>
wrote:
Hi Sean,
Here is create table:
CREATE TABLE ks.cf (
id text PRIMARY KEY,
accessdata blob
) WITH bloom_filter_fp_chance = 0.01
AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
AND comment = ''
AND compaction = {'class': 'org.apache.cassandra.db. compaction.
SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
AND compression = {'chunk_length_in_kb': '64', 'class':
'org.apache.cassandra.io. compress.LZ4Compressor'}
AND crc_check_chance = 1.0
AND dclocal_read_repair_chance = 0.1
AND default_time_to_live = 0
AND gc_grace_seconds = 864000
AND max_index_interval = 2048
AND memtable_flush_period_in_ms = 0
AND min_index_interval = 128
AND read_repair_chance = 0.0
AND speculative_retry = '99PERCENTILE';
Nodetool status:
Datacenter: dc1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/ Moving
-- Address Load Tokens Owns (effective) Host ID
Rack
UN xxxxx 20.66 GiB 256 61.4% f4f54949-83c9-419b-9a43-
cb630b36d8c2 RAC1
UN xxxxx 65.77 GiB 256 59.3% 3db430ae-45ef-4746-a273-
bc1f66ac8981 RAC1
UN xxxxxx 60.58 GiB 256 58.4% 1f23e869-1823-4b75-8d3e-
f9b32acba9a6 RAC1
UN xxxxx 47.08 GiB 256 57.5% 7aca9a36-823f-4185-be44-
c1464a799084 RAC1
UN xxxxx 51.47 GiB 256 63.4% 18cff010-9b83-4cf8-9dc2-
f05ac63df402 RAC1
Datacenter: dc2
========================
Status=Up/Down
|/ State=Normal/Leaving/Joining/ Moving
-- Address Load Tokens Owns (effective) Host ID
Rack
UN xxxx 24.37 GiB 256 59.5% 1b694180-210a-4b75-8f2a-
748f4a5b6a3d RAC1
UN xxxxx 30.76 GiB 256 56.7% 597bac04-c57a-4487-8924-
72e171e45514 RAC1
UN xxxx 10.73 GiB 256 63.9% 6e7e474e-e292-4433-afd4-
372d30e0f3e1 RAC1
UN xxxxxx 19.77 GiB 256 61.5% 58751418-7b76-40f7-8b8f-
a5bf8fe7d9a2 RAC1
UN xxxxx 10.33 GiB 256 58.4% 6d58d006-2095-449c-8c67-
50e8cbdfe7a7 RAC1
cassandra-rackdc.properties:
dc=dc1
rack=RAC1 --> same in all nodes
cassandra.yaml:
num_tokens: 256
endpoint_snitch: GossipingPropertyFileSnitch
I can see cassandra-topology.properties, I believe it shouldn't be there with
GossipPropertyFileSnitch. Can this file be causing any trouble in data
distribution.
cat /opt/cassandra/conf/cassandra- topology.properties
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/ licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Cassandra Node IP=Data Center:Rack
192.168.1.100=DC1:RAC1
192.168.2.200=DC2:RAC2
10.0.0.10=DC1:RAC1
10.0.0.11=DC1:RAC1
10.0.0.12=DC1:RAC2
10.20.114.10=DC2:RAC1
10.20.114.11=DC2:RAC1
10.21.119.13=DC3:RAC1
10.21.119.10=DC3:RAC1
10.0.0.13=DC1:RAC2
10.21.119.14=DC3:RAC2
10.20.114.15=DC2:RAC2
# default for unknown nodes
default=DC1:r1
# Native IPv6 is supported, however you must escape the colon in the IPv6
Address
# Also be sure to comment out JVM_OPTS="$JVM_OPTS -Djava.net.preferIPv4Stack=
true"
# in cassandra-env.sh
fe80\:0\:0\:0\:202\:b3ff\: fe1e\:8329=DC1:RAC3
On Tuesday, June 19, 2018, 12:51:34 PM EDT, Durity, Sean R
<[email protected]> wrote:
You are correct that the cluster decides where data goes (based on the hash of
the partition key). However, if you choose a “bad” partition key, you may not
get good distribution of the data, because the hash is deterministic (it always
goes to the same nodes/replicas). For example, if you have a partition key of a
datetime, it is possible that there is more data written for a certain time
period – thus a larger partition and an imbalance across the cluster. Choosing
a “good” partition key is one of the most important decisions for a Cassandra
table.
Also, I have seen the use of racks in the topology cause an imbalance in the
“first” node of the rack.
To help you more, we would need the create table statement(s) for your keyspace
and the topology of the cluster (like with nodetool status).
Sean Durity
From: learner dba <[email protected]. INVALID>
Sent: Tuesday, June 19, 2018 9:50 AM
To: [email protected]
Subject: Re: RE: [EXTERNAL] Cluster is unbalanced
We do not chose the node where partition will go. I thought it is snitch's role
to chose replica nodes. Even the partition size does not vary on our largest
column family:
Percentile SSTables Write Latency Read Latency Partition Size
Cell Count
(micros) (micros) (bytes)
50% 0.00 17.08 61.21 3311
1
75% 0.00 20.50 88.15 3973
1
95% 0.00 35.43 105.78 3973
1
98% 0.00 42.51 126.93 3973
1
99% 0.00 51.01 126.93 3973
1
Min 0.00 3.97 17.09 61
Max 0.00 73.46 126.93 11864
1
We are kinda stuck here to identify, what could be causing this un-balance.
On Tuesday, June 19, 2018, 7:15:28 AM EDT, Joshua Galbraith
<[email protected]. INVALID> wrote:
>If it was partition key issue, we would see similar number of partition keys
>across nodes. If we look closely number of keys across nodes vary a lot.
I'm not sure about that, is it possible you're writing more new partitions to
some nodes even though each node owns the same number of tokens?
On Mon, Jun 18, 2018 at 6:07 PM, learner dba <[email protected]. invalid>
wrote:
Hi Sean,
Are you using any rack aware topology? --> we are using gossip file
Are you using any rack aware topology? --> we are using gossip file
What are your partition keys? --> Partition key is uniq
Is it possible that your partition keys do not divide up as cleanly as you
would like across the cluster because the data is not evenly distributed (by
partition key)? --> No, we verified it.
If it was partition key issue, we would see similar number of partition keys
across nodes. If we look closely number of keys across nodes vary a lot.
Number of partitions (estimate): 3142552
Number of partitions (estimate): 15625442
Number of partitions (estimate): 15244021
Number of partitions (estimate): 9592992
Number of partitions (estimate): 15839280
On Monday, June 18, 2018, 5:39:08 PM EDT, Durity, Sean R
<[email protected]> wrote:
Are you using any rack aware topology? What are your partition keys? Is it
possible that your partition keys do not divide up as cleanly as you would like
across the cluster because the data is not evenly distributed (by partition
key)?
Sean Durity
lord of the (C*) rings (Staff Systems Engineer – Cassandra)
MTC 2250
#cassandra - for the latest news and updates
From: learner dba <[email protected]. INVALID>
Sent: Monday, June 18, 2018 2:06 PM
To: User cassandra.apache.org <[email protected]>
Subject: [EXTERNAL] Cluster is unbalanced
Hi,
Data volume varies a lot in our two DC cluster:
Load Tokens Owns
20.01 GiB 256 ?
65.32 GiB 256 ?
60.09 GiB 256 ?
46.95 GiB 256 ?
50.73 GiB 256 ?
kaiprodv2
=========
/Leaving/Joining/Moving
Load Tokens Owns
25.19 GiB 256 ?
30.26 GiB 256 ?
9.82 GiB 256 ?
20.54 GiB 256 ?
9.7 GiB 256 ?
I ran clearsnapshot, garbagecollect and cleanup, but it increased the size on
heavier nodes instead of decreasing. Based on nodetool cfstats, I can see
partition keys on each node varies a lot:
Number of partitions (estimate): 3142552
Number of partitions (estimate): 15625442
Number of partitions (estimate): 15244021
Number of partitions (estimate): 9592992
Number of partitions (estimate): 15839280
How can I diagnose this imbalance further?
--
Joshua Galbraith | Senior Software Engineer | New Relic
C: 907-209-1208 | jgalbraith@ newrelic.com
--
Joshua Galbraith | Senior Software Engineer | New Relic
--
Joshua Galbraith | Senior Software Engineer | New Relic
