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Resolving problems & high availability

  1. Building the perfect PHP app for the enterprise Episode 3: Resolving problems & high availability Clark Everetts September 28, 2016
  2. 2 Series overview Now: Resolving problems and high availability October 13: Optimizing performance (revised date) Keep users on your site by learning how to use background jobs and caching, measure performance, and make data-driven decisions.
  3. Clark Everetts Professional services Rogue Wave Software
  4. 4 Agenda 1. How’s your reputation? 2. Monitoring: Know you have a problem 3. Fault diagnosis / Root cause analysis 4. Optimizing scale: Cluster management 5. Synchronizing session data 6. Conclusion 7. Q&A
  5. How’s your reputation?
  6. 6 The cost of a bad rep Complexity Scale ROI DIY Ideal enterprise Volume scales beyond servers Performance degradation Administrativ e costs Not so good reputation • Page delays • Application downtime Good reputation • Responsive under load • Application availability
  7. Monitoring: Know you have a problem
  8. 8 Potential faults “Issues are discussing, problems are for solving.” - Me Fatal PHP errors Out of memory Failed database queries or updates Network connectivity (no connection) Application Non-fatal PHP notices, warnings Slow functions or request executions High memory consumption Network (degraded) Application logic
  9. 9 The problem with problem resolution • Most problem resolution time is spent identifying root cause • Problem reproduction is often difficult and time-consuming • Many possible sources: server load, input data, database state, etc.
  10. 10 Problem identification • Do you know you have a problem? – Your phone is ringing? – Getting emails? – Monitoring tools or services? • Is a problem brewing that customers don’t see … yet? Analyze information • Debugging • Logging (files, events database, application level logs) Recreate problem With enough relevant information: • Reproduce in order to troubleshoot and verify a fix • Can we identify the cause without having to reproduce? Gather information • What information can you collect?
  11. 11 Monitoring for faults • Scan log files (not manually!) – Web server access and error logs – PHP error log (php.log) – Application-specific logs (filesystem, database) • Don’t log noise • Avoid logging to php.log • ZendLog, Monolog, error_log() • Event-based monitoring – Recorded in event database, visible in UI, accessible via API – Optional automatic notification via email alerts – Optional callback URIs for integration with other monitoring tools
  12. 12 Monitoring events
  13. 13 Event rules
  14. 14 Sampling of event types • Custom event • Database error • Function error • High memory usage • Inconsistent output size • Job execution delay/error • Job logical failure • PHP error • Slow function execution • Slow query execution • Slow request execution • Zend Framework exception
  15. 15 Example Results: Users never experienced a problem Development team solidified “trust factor” with management Requirements: Stale data is unusable data “Soft” performance criteria (user’s say when “good enough”) Problem: New feature of internal application suffered slow performance due to large database result sets from complex queries. Challenge: Prior to rollout, isolate which queries were experiencing the slowest response times, make improvements, & cache results if possible Used: Zend Server Monitoring, IBM i DB2 index analyzer, and Zend Server Data Cache
  16. Poll #1 How do you discover problems in your applications? - Notified by a person (phone call, email, cubicle visit) - Notified by an in-house automated tool - Notified by commercial automated tool (Zend, New Relic)
  17. Fault diagnosis / Root cause analysis
  18. 18 Root cause analysis • Log files – Can both indicate a problem, and contain necessary diagnostics • Monitoring tools may provide further info on: – Failed function call arguments – High memory consumption – Etc. • printf() and var_dump() • Debuggers (Xdebug, Zend Debugger, phpdbg) • Code tracing pinpoints in the request execution what triggered the problem • Z-Ray: request details right in the developer’s web browser (code trace- like)
  19. 19 Event details
  20. 20 Debugging
  21. Poll #2 What is your primary means of root cause analysis? - printf(), var_dump() - Logging data to files - Xdebug - Zend debugger - phpdbg
  22. Optimizing scale: Cluster management
  23. 23 What is a cluster?
  24. 24 Why cluster? • Long-term demand is increasing – Growing population of mobile devices – Machine-to-machine traffic (bots, B2B, APIs) on the rise • Demand is both predictable and unpredictable – “The Witching Hour” and other periodic processing spikes • Resilience when failures occur Clustering allows you to • Adapt to changing demand • Manage infrastructure costs • Provide redundancy in the face of failures
  25. 25 Cluster overview Requests Responses
  26. 26 Cluster characteristics • Nodes are the same – Any node can do the same work as all others – Same specs • Operating system, installed software base • Hardware (RAM, disk, etc.) • Virtual machines – Containerization and provisioning (Docker, Rocket, Puppet, Chef, Ansible, SaltStack, Fabric, Capistrano, etc.) Provides for: • Scaling out/in as traffic increases/decreases • Redundancy in the face of failures
  27. Synchronizing session data
  28. 28 Load balancing and sessions Session Affinity (Sticky Sessions)
  29. 29 Session clustering
  30. 30 Session clustering
  31. 31 Session clustering
  32. 32 Best practices How do you know? • Monitoring How do you diagnose? • Log files • Code tracing • Z-Ray How do you prevent? • Testing! • Load balancing • Clustering How do you minimize downtime? • Support
  33. Poll #3 How do you currently implement high availability sessions in a clustered environment? - Central database (MySQL, PostgreSQL, Oracle, MariaDB) - Memcached - Redis - Zend Server - Other/We’re not clustered
  34. 34 Conclusion • Reputation = f(reliability) + f(availability) • Monitor for faults: know quickly when you have a problem • Fault diagnosis is all about using the right tools • Q: Scalability? A: Clustering! • Sessions in clusters Visit for webinars Visit for the Zend Developer Zone
  35. Q & A
  36. 36 The fastest way to enterprise PHP Free trial • Full, tested, secure PHP stack • Z-Ray vision deep into your app • Code tracing • Job queuing and caching • Deployment and DevOps • High availability session clustering • Backed by support & services
  37. 37 Series overview October 13: Optimizing performance (revised date) Keep users on your site by learning how to use background jobs and caching, measure performance, and make data-driven decisions.
  38. 38 Don’t miss this premiere PHP event! Register at Visit with sponsors 90+ sessions in 6 tracks
  39. 39 Watch on demand • Watch this webinar on demand • Read the recap blog to see the results of the polls and Q&A session
  40. Building the perfect PHP app for the enterprise Episode 3: Resolving Problems & High Availability Clark Everetts September 28, 2016