ZooKeeper is a service for coordinating processes within distributed systems. Stress test of the tool was applied. Reliable Multicast and Dynamic LogBack system Configuration management were implemented with ZooKeeper. More details: http://proskurnia.in.ua/wiki/zookeeper_research

1. ZooKeeper
Iuliia Proskurnia, Zygimantas Bruzgys

2. Outline
• ZooKeeper? • Experiments
• ZooKeeper Service • Configuration
• ZooKeeper Usage • Reliable Multicast
• Key Points
• Stress Test
• Installation
• Conclusions
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3. Key features
ZooKeeper is: Features are:
•Service for coordinating •High Throughput
processes in distributed
applications. •Low Latency
•Key/value table. •Highly Available
•No locks service. •Strictly ordered access to the
nodes
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4. Architecture
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5. ZooKeeper Service
• Znodes • Guarantees:
• Regular & Ephemeral • Linearizable writes
• Watches • FIFO client order
• Handling shared configuration
• Synchronous
and updates
Asynchronous methods
• Liveness and durability
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6. ZooKeeper Usage
• Simple Locks
• Configuration Management
• Simple Locks without Herd Effect
• Group membership
• Read/Write Locks
• Leader Election
• Double Barrier
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7. Key Points
• Wait-free protocol
• No Locks • But...
• Support Applications: • State Based System
• Configuration Management • Last changes visible
• Leader Election • Limited total size of data
• Group Membership
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8. Installation
To install you need to: Sample Configuration File:
•Install Java tickTime=2000
initLimit=10
•Download and extract syncLimit=5
clientPort=2181
ZooKeeper dataDir=/home/ubuntu/zoodata
•Write a configuration file server.1=10.227.206.23:2888:3888
•Write node ID in data server.2=10.58.190.233:2888:3888
server.3=10.234.121.38:2888:3888
directory (filename myid)
•Start ZooKeeper
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9. Experiments
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10. Configuration Management
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11. Reliable Multicast: Main
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12. Reliable Multicast: Leader Election
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13. Reliable Multicast:
Send Message
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14. Reliable Multicast: Receive Message
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15. Reliable Multicast:
Interesting Cases
• New client connects while a message is multicasted
• Recipient fails before receiving a message
• Leader fails
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16. Stress Tests
• Done with zk-latencies Python script
• Run with the following configuration
./zk-latencies.py --servers "CONNECTION_STRING" --znode_count=ZNODE_COUNT
--znode_size=100 --timeout=5000 --watch_multiple=2
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17. Stress Tests
14000"
Time#for#10.000#Async#Opera>ons#
12000"
10000"
8000"
Read" 1 client,
ms#
6000"
Write" multiple
4000" Watch"
servers
2000"
0"
1" 2" 3" 4" 5"
Number#of#Servers#in#ZooKeeper#Cluster#
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18. Stress Tests
7"
Synchronous+Opera)ons+
6"
5"
ms/opera)on+
4"
Read" 1 client,
3" Write" multiple
Watch"
2" servers
1"
0"
1" 2" 3" 4"
Number+of+Servers+in+ZooKeeper+Cluster+
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19. Stress Tests
1,2"
Writes+per+ms+
1"
ms/opera)on+
0,8"
0,6"
5 servers,
0,4" 1 client
0,2"
0"
1" 2" 4" 6" 8" 10" 12" 14" 16"
Thousands+of+Async+Opera)ons+
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20. Conclusions
• ZooKeeper is: • WeShowed Several
Examples:
• Coordination Service
• Configuration Management
• Highly Available
• Reliable Multicast
• Low Latency
• Wait-Free
• Stress Tests Shows:
• Prefer more servers for high availability and
higher reads/write ratio
• With more servers it is still low latency
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21. ZooKeeper
Iuliia Proskurnia, Zygimantas Bruzgys