Are you a MySQL DBA or DevOps individual being asked to run Cassandra or Scylla? Feeling overwhelmed? In this talk, I will present Cassandra/Scylla operations in terms that directly relate to MySQL. I will show you comparisons between the Information Schema and the Cassandra/Scylla System keyspace(s). I will also talk about metrics available in MySQL versus Cassandra/Scylla and how to retrieve them. Finally, I will talk about how MySQL replication compares with Cassandra replication. Hopefully, when I am done you will be able to relate to Cassandra operations in a practical and useful way.

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How to Run Cassandra/Scylla from
a MySQL DBA's Point of View
Principal Consultant, The Pythian Group
John Schulz

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John Schulz
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John has 40 of years experience working with data.
Data in files and in Databases from flat files through
ISAM to relational databases, and most recently
NoSQL. For the last 15 years, he's worked on a
variety of Open source technologies including
MySQL, PostgreSQL, Cassandra, Riak, Hadoop, and
Hbase. He has been working with Cassandra since
2010. For the last three years, he has been working
for The Pythian Group to help their customers
improve their existing databases and select new
ones for new applications.

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3© The Pythian Group Inc., 2017
Systems currently
managed by Pythian
EXPERIENCED
Pythian experts
in 35 countries
GLOBAL
Millennia of experience
gathered and shared
over 19 years
EXPERTS
11,800 2400

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Agenda
▪ Instrumentation
▪ MySQL Schemas (databases)
▪ Cassandra Schemas (databases)
▪ Nodetool commands
▪ Forget the CLI? Graphical Alternatives
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Instrumentation
▪ In order to manage software it needs to be instrumented
▪ What does that mean?
o Counters – how many of what
o Timers – how long things take
o Configuration – what are the current settings
o Commands – start, stop, status, change
▪ MySQL makes heavy use of Schemas (databases) to expose
instrumentation
▪ Cassandra/Scylla use Schemas (keyspaces) as well but not as much
▪ Both use alternative commands to access instrumentation as well
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The Command line

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The MySQL Schemas (databases)
▪ Mysql – Identity, authorization, slow log, and a few other things
▪ Information_schema – Table and view structures, table stats, and
counters
▪ Performance_schema – Detailed tracing of recent requests
▪ Sys – Simplification of the performance_schema
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Cassandra/Scylla Keyspaces (Schemas)
▪ System – Cluster management
▪ System_schema – Table and view structures
▪ System_auth – Identity and authorization
▪ System_distributed – More Cluster management
▪ System_traces – Tracing data similar to MySQL
Performance_schema
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MySQL Show and Describe
▪ Describe is used to describe table definitions and query plans
o Describe table;
o Describe query;
▪ Show is used to provide access to much other instrumentation
o Show processlist; - list active queries currently running
o Show variables; - list configuration information
o Show global status; - List counter and other dynamic values
o Show table status; - Get information about Table sizes
o Lots more
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Cassandra/Scylla Describe and nodetool
▪ Describe is used to show information about keyspaces and tables
o Describe keyspaces;
o Describe keyspace spacename;
o Describe tablename;
▪ Nodetool command and control command line interface
o Status – show status of a cluster
o Tpstats – show threadpool counters
o Tablestats – show table sizes and access counts
o Tablehistograms – Show table access data in histogram form
o Proxyhistograms – Show node access data in histogram form
o Lots of other commands
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Cassandra/Scylla Describe
ccm node1 cqlsh
Connected to ver_3.11 at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 3.11.0-SNAPSHOT | CQL spec 3.4.4 | Native protocol v4]
Use HELP for help.
cqlsh> desc keyspaces;
modal system_schema system_auth system system_distributed system_traces
cqlsh> desc modal;
CREATE KEYSPACE mmodal WITH replication = {'class': 'NetworkTopologyStrategy', 'dc1': '3', 'dc2': '3'} AND durable_writes =
true;
CREATE TABLE modal.phi_audit (
tennant text,
user text,
application text,
log_time timestamp,
doc_list frozen<list<text>>,
ip_address inet,
patient_id uuid,
PRIMARY KEY ((tennant, user), application, log_time);
) WITH CLUSTERING ORDER BY (application ASC, log_time ASC);
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Nodetool Status
[jschulz@Snoopy-3 ~]$ ccm node1 nodetool status
Datacenter: dc1
===============
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 127.0.0.1 315.37 KiB 256 100.0% daf8f3a5-122d-4c66-9018-94c71e7076d0 r1
UN 127.0.0.2 305.65 KiB 256 100.0% 880a9408-1ee7-4128-a555-2edf4098bfd9 r1
UN 127.0.0.3 323.42 KiB 256 100.0% c0e7e6dc-5c35-40de-8cb6-492925ca1e19 r1
Datacenter: dc2
===============
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 127.0.0.4 323.8 KiB 256 100.0% cde47697-9c8c-4a4d-9f24-ae250eb07145 r1
UN 127.0.0.5 322.97 KiB 256 100.0% 59e8f859-d2b4-49f7-9f2a-4184744b33a0 r1
UN 127.0.0.6 323.89 KiB 256 100.0% 96ca12a3-cf26-4456-8b15-41dc7eb357ff r1
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Nodetool Proxyhistograms
[jschulz@Snoopy-3 ~]$ ccm node1 nodetool proxyhistograms;
proxy histograms
Percentile Read Latency Write Latency Range Latency CAS Read Latency CAS Write Latency View Write Latency
(micros) (micros) (micros) (micros) (micros) (micros)
50% 454.83 42.51 1629.72 0.00 0.00 0.00
75% 654.95 61.21 2816.16 0.00 0.00 0.00
95% 17436.92 182.79 2816.16 0.00 0.00 0.00
98% 17436.92 785.94 2816.16 0.00 0.00 0.00
99% 17436.92 1955.67 2816.16 0.00 0.00 0.00
Min 61.22 20.50 379.02 0.00 0.00 0.00
Max 17436.92 5839.59 2816.16 0.00 0.00 0.00
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Nodetool Tablehistograms
[jschulz@Snoopy-3 ~]$ ccm node1 nodetool tablehistograms keyspace1 standard1
keyspace1/standard1 histograms
Percentile SSTables Write Latency Read Latency Partition Size Cell Count
(micros) (micros) (bytes)
50% 3.00 9.89 73.46 258 5
75% 3.00 11.86 88.15 258 5
95% 3.00 14.24 263.21 258 5
98% 3.00 17.08 1131.75 258 5
99% 3.00 17.08 3379.39 258 5
Min 2.00 4.77 17.09 180 5
Max 3.00 17.08 186563.16 258 5
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Nodetool TPstats
[jschulz@Snoopy-3 ~]$ ccm node1 nodetool tpstats
Pool Name Active Pending Completed Blocked All time blocked
ReadStage 0 0 4008933 0 0
CompactionExecutor 0 0 383096 0 0
MutationStage 0 0 3219638 0 0
MemtableReclaimMemory 0 0 603 0 0
GossipStage 0 0 2457780 0 0
RequestResponseStage 0 0 3231941 0 0
Native-Transport-Requests 0 0 10891424 0 0
MigrationStage 0 0 8 0 0
MemtablePostFlush 0 0 653 0 0
PerDiskMemtableFlushWriter_0 0 0 603 0 0
MemtableFlushWriter 0 0 603 0 0
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Nodetool Tablestats
▪ Keyspace : keyspace1
▪ Read Count: 7766215
▪ Read Latency: 0.19810779948791013 ms.
▪ Write Count: 3219609
▪ Write Latency: 0.040600896257899644 ms.
▪ Pending Flushes: 0
▪ Table: standard1
▪ SSTable count: 5
▪ Space used (live): 248645402
▪ Space used (total): 248645402
▪ Space used by snapshots (total): 0
▪ Off heap memory used (total): 1404056
▪ SSTable Compression Ratio: -1.0
▪ Number of keys (estimate): 389445
▪ Memtable cell count: 38904
▪ Memtable data size: 10854216
▪ Memtable off heap memory used: 0
▪ Memtable switch count: 65
▪ Local read count: 7766215
▪ Local read latency: 0.343 ms
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Nodetool TableStats
Local write count: 3219609
Local write latency: NaN ms
Pending flushes: 0
Percent repaired: 0.0
Bloom filter false positives: 247
Bloom filter false ratio: 0.00001
Bloom filter space used: 1232672
Bloom filter off heap memory used: 1232632
Index summary off heap memory used: 171424
Compression metadata off heap memory used: 0
Compacted partition minimum bytes: 180
Compacted partition maximum bytes: 258
Compacted partition mean bytes: 258
Average live cells per slice (last five minutes): 1.0
Maximum live cells per slice (last five minutes): 1
Average tombstones per slice (last five minutes): 1.0
Maximum tombstones per slice (last five minutes): 1
Dropped Mutations: 0
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Nodetool Describecluster
Cluster Information:
Name: ver_3.11
Snitch: org.apache.cassandra.locator.DynamicEndpointSnitch
Partitioner: org.apache.cassandra.dht.Murmur3Partitioner
Schema versions:
ee5e8a83-e806-3b31-aec6-17afe768c734: [127.0.0.1, 127.0.0.2, 127.0.0.3,
127.0.0.4, 127.0.0.5, 127.0.0.6]
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Alternatives to the
Command Line

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Alternatives
▪ Why do we want to use something other than the command line?
o History
o Graph views on the fly -
o Alerts
o Aggregated data from all nodes at once
o Graphical correlations
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Grafana view of a Cassandra cluster monitored by Prometheus
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What are some of the alternatives
▪ Proprietary
o Datadog - https://www.datadoghq.com/
o New Relic - https://newrelic.com/
▪ Open source
o Prometheus - https://prometheus.io/
o Zabbix - https://www.zabbix.com/
o Lots of others
▪ Log Aggregators
o ELK – Open source -
o Splunk – Proprietary -
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THANK YOU
schulz@pythian.com
@jschulz907
Please stay in touch
Any questions?