cisco: application clustering with couchbase – couchbase connect 2016
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Clint Ricker
Couchbase Application Clustering
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• Solutions Architect, Office of the CTO
• SP Video
Me
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• Shipping Couchbase in service provider grade software since 2012
• Running in mission critical, very large scale on-prem and AAS offerings around the world
• Datasets of billions of records
Cisco / Couchbase
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• Creating a clustered application glued together by Couchbase
• Use Couchbase / lightweight code snippets instead of common datacenter technologies
• Replacing Zookeeper, Eureka, Consul, Rabbit/HornetMQ, etc…
What
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What
App Instance
App Instance
App Instance
Couchbase
App Instance
App Instance
App Instance
Couchbase Shared Storage
Dependent Databases
Zookeeper
Consul
RabbitMQ
Load Balancer Load Balancer
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• Complexity kills • Lower machine count• Organizational needs• Application needs• Love of roll your own• Very minimal feature set
Why
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• More application code to maintain• Schema changes are difficult• Existing platform stack • Less sensitivity to deployment
footprint• Very minimal feature set
Why not
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Global Distributed Lock
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Global Distributed Lock
• Used to ensure certain activities are globally serialized
• Typically provided by Consul / Zookeeper / etc
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Global Distributed Lock
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Global Distributed Lockuint64_t CBGetLock(char *lockKey, int objectLockTimeout) {
if (status == CBSTATUS_SUCCESS) { for (i = 0; i < retries; i++) { status = CBObjGet(buf, &cas, lockKey,objectLockTimeout); if (status >= 0) { return cas; } } } return CBSTATUS_FAILURE;}
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Leader Election
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Leader Election
• Used to have a dynamically dedicated master instance for ongoing activity
• Common for frequent maintenance needs
• Typically provided by Consul, Zookeeper, etc…
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Leader Election
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Leader Electionuint64_t CBElectMasterPrivate(char *masterKey, int ttl, uint64_t masterKeyCas) {
if (masterKeyCas > 0) { status = CBObjReplace(masterKey, "master", masterKeyCas, ttl); } else { status = CBObjSet(masterKey, "master", masterKeyCas, ttl); }
if (status == CBSTATUS_SUCCESS) { for (i = 0; i < retries; i++) { status = CBObjGet(buf, &cas, masterKey, NOLOCK); if (status >= 0) { return cas; } } CBObjDeleteCas(masterKey, cas); return CBSTATUS_FAILURE; } return CBSTATUS_FAILURE;}
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Discovery Service
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Discovery Service
• Used to discover endpoints for specific services or the total set of nodes in the cluster
• Supports basic load balancing and health check
• Often provided by Consul, Eureka, DNS, etc…
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Advertise
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<NodeList><Node>
<NodeName>appInstance1</NodeName><Updated>2016-10-24T12:23:42Z</Updated><Address>172.31.31.15:80</Address>
</Node></NodeList><NodeList>
<Node><NodeName>appInstance2</NodeName><Updated>2016-10-24T12:23:41Z</Updated><Address>172.17.126.2:80</Address>
</Node></NodeList>
Example
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Discovery
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Discovery
Couchbase
App2 Service Instance
App2 Service Instance
App2 Service Instance
App1 Service Instance
Advertise “foo”, “instance ip address”
Lookup “foo”, choose instance Send request to address of selected instance
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Shared Queues
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Shared Queues
• Create shared queues that are polled by set of nodes
• Typically provided by HornetQ, RabbitMQ, etc…
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Shared Queue Add
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Shared Queue Read
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Transactions
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Transactions
• Create a generic globally shared transaction system with rollback
• Typically provided by HornetQ, RabbitMQ, etc…
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Transactions
App1 Service InstanceIncoming request
App2 Service Instance
App2 Service Instance
App1 Service InstanceApp1 Service Instance
LB
Service requestw/callback URL
Service requestw/callback URL
Callback
Callback
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If transaction failed or timed out
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2
Create Transaction
Transaction State Record w/state=active and time=currentTime
Transaction Log Record
1
2
4
Close Transaction
Delete Transaction State Record
Delete Transaction Log
1
2
3
RollbackEither synchronously with failure or discovered through query of transaction state records
Pull transaction log
Iterate through transaction log in reverse
Undo each activity
1
2
3
Transactions
Update Transaction state record with state=active and time=currentTime
Append Activity to Transaction Log Record
1
2
Execute Activity
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