3450 - Writing and optimising applications for performance in a hybrid messaging world
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The document discusses performance optimization for IBM MQ messaging applications, detailing various performance bottlenecks, improvements in versions, and recommendations for application design. Key topics include the importance of message persistence, performance implications of connection binding, and enhancements in the queue manager's structure to improve scalability and efficiency. It also covers logging, recovery, and the significance of understanding application patterns to enhance throughput and reduce latency.
3450 - Writing and optimising applications for performance in a hybrid messaging world
- 1. 3450: Writing and optimising Applications for performance in a hybrid messaging world Tim McCormick IBM MQ Service Architect timmccor@uk.ibm.com
- 2. Agenda • Some performance numbers • Structure of the Queue Manager • Function Walkthroughs • Client Channels • Logging and Recovery
- 3. Agenda • Some performance numbers • Structure of the Queue Manager • Function Walkthroughs • Client Channels • Logging and Recovery
- 4. Performance Bottlenecks • Business Systems are complex – Often no single bottleneck limiting performance – Performance can mean different things to different people – Throughput • Scalability • Low resource usage • Not only limited by physical resources – Application design, such as parallelism can have major effect • Performance Reports (from SupportPac site) show range of scenarios RAM CPU NetworkI/O Bottlenecks
- 5. See how far it's come …
- 6. Distributed Performance: Persistent Messaging • An AIX system: Max performance increased from 16K to 19K
- 7. Distributed Performance: Non-persistent Messaging • A Windows system: Max performance increased from 90K to 121K
- 8. Distributed Performance in V8 • Improvements to distributed queue manager scaling – Improve efficiency – Better exploitation of wider SMP machines – Looking at customer-provided application patterns not just benchmarks • Always happy to have more customer examples • Multiplexed client performance – Increase the performance of multiplexed client channels (SHRCONV > 0) – Especially for SHRCONV=1 • Other areas that helped: – Cache alignment for internal structures – Extended 64-bit exploitation for locking primitives – RFH2 handling, particularly for waiting-getter • Fewer copies of data are needed – Better compiler optimisations including feedback-directed optimisation – Faster data conversion (especially for 1208) • Many messages are in 1208 codepage • Optimised handling when the queue manager needs to convert them
- 9. Agenda • What is distributed WebSphere MQ? • Structure of the Queue Manager • Function Walkthroughs • Client Channels • Logging and Recovery
- 10. Also: runmqchi runmqlsr amqzdmaa amqrmppa amqpcsea Queue Manager Process Tree Execution Controller (amqzxma0) Critical Services (amqzmuc0) Restartable Services (amqzmur0) External Processes (amqzmgr0) Repository Manager (amqrrmfa) Object Authority Manager (amqzfuma) LQM Agent (amqzlaa0) V6V7.x, V8 PubSub V6 Compat (amqfqpub) PubSub Streams (amqfcxba) PubSub Utils (amqzmuf0) Dur/Subs Mgr Topic Scavenger Multicast Brw/Mark Delayed Deliv Cache, Inter QMgr
- 11. Agent Queue Manager Shared Resources Checkpoint MQCONN MQCONN MQOPEN MQDISC MQPUT MQGET etc. Agent IPCC Execution Controller IPCC Log Manager MQI Stub Application IPCC MQI Stub Application IPCC MQI Stub Application IPCC Object Authority Manager Queue Manager: Process Model Shared, Isolated and Trusted Bindings
- 12. Agenda • What is distributed WebSphere MQ? • Structure of the Queue Manager • Function Walkthroughs • Client Channels • Logging and Recovery
- 13. MQI Stub Application IPCC Execution Controller IPCC IPCC DAP Kernel Agent IPCC Application (MQI Stub) Verify parameters and handles Construct a Connect message Call API crossing exit Send a message to the EC Application (MQI Stub) Receive the reply Construct an IPCC message Send the message to the agent Application (MQI Stub) Receive reply and call API crossing exit Return HCONN Execution Controller Choose an agent or start a new one Construct a reply IPCC message Return reply to application Agent Check App's permission to connect Allocate and assign agent resources Send IPCC reply back to application MQCONN
- 14. Performance Implications: Connection Binding • Fastpath binding removes inter-process communications – Implies that the application is 'trusted' – MQCONNX option MQCNO_FASTPATH_BINDING – Application failure can corrupt queue manager • Primary benefit is for non-persistent message processing – Use for MCAs, Broker • - 30% CPU saving MQ Appl Agent Memory Log IPC Standard Binding MQ Appl Agent Memory Log FASTPATH Binding
- 15. Performance Implications: Connection Binding MQ Appl Agent Memory Log IPC Standard Binding MQ Appl Agent Memory Log FASTPATH Binding MCA Agent Memory Log IPC Client Binding MQ Appl Network
- 16. Application (MQI Stub) Verify hConn Call API crossing exit Verify parameter addressability Place parameters in an Open message Send an IPCC message to the agent MQI Stub Application IPCC DAP Kernel Agent IPCC Agent Application interface Verify open parameters Kernel Verify operation validity Resolve target – including cluster lookup Check permissions on the queue DAP Load the queue ready for gets and puts if required ƒ This is the part that can use system resources Kernel Generate handle to object for application Generate responses and event messages IPCC Send reply back to application Application (MQI Stub) Receive reply Call API crossing exit Return HOBJ MQOPEN of a queue
- 17. MQOPEN internal changes for V8 • The object catalog is the list of objects and a map to the real files – Shows that queue 'X.Y' is stored in "/var/mqm/qmgrs/<qm>/queues/X!Y" – dspmqfls command shows the map – Updated whenever an object is created or deleted • In MQ V7 there were just two locks associated with the object catalog – A significant implication of this scheme was that an MQOPEN could not overlap with the creation/deletion of a queue (or any other object) – Ghost queues introduced in MQ V5.2 went some way to reducing the impact, particularly for TDQ’s, but very significant serialization implications remained. • MQ V8 uses finer grained locks – The master mutex need not be owned while waiting for the object mutex. • The most significant impact of this serialization change is that dynamic queues can now be created and destroyed concurrently with MQOPEN activity 26
- 18. Performance Implications: Heavyweight MQI Calls • MQCONN is a “heavy” operation – Don’t let your application do lots of them – Wrappers and OO interfaces can sometimes hide what’s really happening – Lots of MQCONNs can drop throughput from 1000s Msgs/Sec to 10s Msgs/Sec • MQOPEN is also ‘heavy’ compared to MQPUT/MQGET – Depends on the type of queue and whether first use • Loading pre-existing queue; creating dynamic queue – It’s where we do the security check • Try to cache queue handles if more than one message – If you’re only putting one message consider using MQPUT1 • Particularly client bindings • Try to avoid exclusive access to the Queue – Makes it harder to scale the solution • For example adding more instances of application – Implies that reliance on message order is not required • Partition the data to allow parallel processing?
- 19. Performance Implications: Persistence • Log bandwidth is going to restrict throughput – Put the log files on the fastest disks you have, separate from queue file – Persistent messages are the main things requiring recovery after an outage – Can significantly affect restart times • Why use persistence? – False assumption that persistence is for "important" data and nonpersistent for when you don't care – The real reason for persistent messages is to reduce application complexity – With persistent, apps do not need logic to detect and deal with lost messages – If your app (or operational procedures) can detect and deal with lost messages, then you do not need to use persistent messages • Understand which apps use persistence MQPUT Queue File Log
- 20. Kernel Verify operation validity (Resolve cluster queue destination) DAP Reserve space for the message data If (persistent message) Write log records for the update (Wait for log records to reach the disk if outside syncpoint) Write the message to the queue file Else (non-persistent) If (space available in queue buffer) Copy the message data into the buffer Else Write the message to the queue file without logging Maintain queue statistics such as queue depth Kernel Generate responses and events, wakeup getters/drive async consumers Serialised MQPUT Walkthrough Also check for "if waiting getter" Tip! Use persistent messages with syncpoint
- 21. Put to a waiting getter • MQPUT most efficient if there is getting application waiting – Having multiple applications processing queue increases percentage – May not appear ‘balanced’ – May keep one ‘hot’ • Only for out of syncpoint messages – Both persistent and non-persistent – If Persistent outside of syncpoint, think carefully about why using persistence • Got message could be lost if crash before returning to the application! • No queuing required – Removes a lot of processing of placing the message onto the queue • Significantly reduces CPU cost and improves throughput – Lots of improvements on this area in newest releases (7.1, 7.5) MQPUT MQGET MQGET MQGET
- 22. Kernel Verify operation validity Check message expiry Wait for message if not available DAP Locate a message meeting the requested criteria including current browse cursor position priority message id, correlation id, segment or group conditions Copy data into the message buffer If (persistent) Write log record (Wait for log record to reach the disk if outside syncpoint) Move the browse cursor if required Maintain queue statistics such as queue depth Kernel Generate responses and events Serialised MQGET Walkthrough Tip! In request reply model, get by correlid more efficient than get by msgid
- 23. Kernel Verify operation validity DAP Write log record to end transaction Wait for this log record to reach the disk Lock all queues touched in this transaction For each queue Make any changes to messages in the transaction visible Unlock queue Kernel Generate responses and events Wakeup Getters/Drive Async Consumers MQCMIT Walkthrough Deal with 2PC protocol if in an XA transaction
- 24. Performance Implications: Syncpoint • Do you need it? – Yes, when a set of work needs to either all be performed, or all not performed • Maximum Size of UOW can be limited – QMGR MAXUMSGS parm – Set to sensible value to avoid runaway applications • Make sure you keep the size of your UOWs small – Don’t forget to end the UOW • Cheaper to process in syncpoint for persistent messages – Up to a point, not huge UOWs – Log not forced after every MQPUT/MQGET • Useful even when only a single message inside syncpoint – And running multiple parallel applications
- 25. Good Application Design - Summary • Long-running connection • Opens queues up-front • Uses syncpoint for persistent operations • No message affinities so multiple instances can run in parallel
- 26. Agenda • What is distributed WebSphere MQ? • Structure of the Queue Manager • Function Walkthroughs • Client Channels • Logging and Recovery • Multiple Installation Support
- 27. Clients from V7 • Many changes to the client protocols in V7 – All can improve performance • Multiplexing or Shared Conversations – For multi-threaded applications – Several connections use the same socket • Asynchronous Put – For sending applications • Read-ahead – For receiving applications • New threads inside application for full-duplex comms – Sharecnv(0) – May be fast but no full-duplex so miss good functionality – Sharecnv(1) – One socket per hconn, optimised in V8 - recommended value – Sharecvn(10) – Shared socket for multiple conversations (default value)
- 29. Read-ahead of messages Client MQCONN MQOPEN MQGET MQGET MQGET Server Request for ‘n’ messages
- 30. Client Connection Performance. • Lots of internal changes at V8 – Channel status table restructure – Reduce cost of health checking (MQIBindType=FASTPATH) – Keep a hash table of processes, each with a sub-list of threads. – Reduce cost of creating/deleting TDQ’s – Channel process pooling pre-start • Net effect of all of these changes is significant improvement to the queue manager’s ability to accept a large number of inbound connections in a relatively short time. • In one test the time taken to attach 50,000 clients, with each client owning a TDQ, reduced from over an hour at 7.0.1.6 to under 4 minutes at MQ V8. 58
- 31. Agenda • What is distributed WebSphere MQ? • Structure of the Queue Manager • Function Walkthroughs • Channels • Logging and Recovery • Multiple Installation Support
- 32. What's the point of logging? • A log record is written for each persistent update – The log record describes the update • Optimisations to minimise serialisation points • Write-Ahead Logging – The log is always more up-to-date than the actual data • Log is a sequential file – Sequential I/O is much quicker than random – Single point of writing rather than to individual object files • Log and actual data are reconciled during strmqm – Progress information displayed • Point of consistency – Checkpoint – Log control file: amqhlctl.lfh – in log directory – Checkpoint amqalchk.fil – qmgr directory – Backup queue managers from MQ V6 Myth! Triple write integrity does not mean we write all data 3 times!
- 33. Looking at logger performance • Can extract internal information from a service tool – Lots of MQ performance PMRs turn out to be disk-related. So recording was added to the internal state • amqldmpa –c H –m <qmgr> -d 8 –n <count> -s <interval> -f <file> – The amqldmpa program can dump lots of other internal information too • Includes logger I/O activity – WriteTimeMax shows maximum time (microseconds) to complete I/O – WriteSizeMax shows largest (bytes) I/O – Since qmgr started • Maintains averages – WriteSizeShort is short-term (64-sample) weighted average of recent writes – WriteSizeLong is longer-term (1024-sample) weighted average – Similarly for WriteTimeShort/Long • From one PMR: – WriteTimeMax = 59102377, WriteSizeMax=2097152 – So it has taken nearly 60 seconds to write 2MB – Implies they need to talk to disk support team!
- 34. Summary – understand the applications • Understand the application pattern – Exclusivity, affinity • Understand the individual application – Many times have heard "it's using persistence" when it's not. Or vice versa. • If you don't have access to application source, tools exist to help – Application Activity Trace – Accounting messages – MQ Trace
- 35. Questions?
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- 39. Monday 10:30-11:30 3592 New MQ features 3452 Managing applications 12:00-13:00 2835 MQ on z/OS and Distributed 15:00-16:00 3470 Latest MQ z/OS features 2833 Where is my message? 3544 MQ Light in an MQ infrastructure 16:30-17:30 3573 Hybrid cloud messaging 2941 MQ Advanced Tuesday 08:30-09:30 3540 The MQ Light API 12:00-13:00 3456 The IBM MQ Appliance 13:15-14:15 3499 Introducing Message Hub 3458 MQ Appliance administration 14:30-15:30 6432 MQ updates and futures (InnerCircle) 2849 Messaging feedback roundtable 16:00-17:00 3544 MQ Light in an MQ infrastructure 3513 MQ hands on lab Wednesday 08:30-09:30 3602 Managing your MQ environment 12:00-13:00 3613 Designing MQ self service 6408 Hybrid messaging roadmap (InnerCircle) 13:15-14:00 3416 HA and DR with MQ 3433 Why secure your messaging? 15:45-16:30 3429 Securing MQ 2847 Meet the messaging experts 16:00-17:00 3508 MQ Light hands on lab 16:45-17:30 2275 Migrating to the IBM MQ Appliance Thursday 08:30-09:15 3420 MQ Clustering 2931 Business agility with self service MQ 09:30-10:15 3479 MQ z/OS clusters and shared queue 3450 Optimising MQ applications 2849 Messaging feedback roundtable 10:30-11:15 3465 MQ Appliance high availability 3481 MQ z/OS messaging connectivity 11:30-12:15 3474 Active-active messaging 3537 Monitoring and managing MQ 3425 MQ publish/subscribe Find us at the EXPO: Hybrid Integration peds 65-68 Check out the Hybrid Messaging sub topic under the Hybrid Integration topic for further customer and business partner sessions Hybrid Messaging from the IBM experts at InterConnect 2016 Sunday 14:30-15:30 6408 Hybrid messaging roadmap (InnerCircle)