1. Mission critical application testing with Distributed Replay
Joe Yong
Senior Program Manager

2. Distributed Replay What is Distributed Replay?
Multi-client scalability to drive higher throughput
Higher workload replay fidelity
Useful for stress testing production workload or performing application compatibility testing before upgrades
Why an enhanced replay tool?
Use multiple low-cost clients (workstations) to handle large workload traces within reasonable time
Address limitations of current SQL Trace based tools (Profiler, Upgrade Assistant)
Provide enhanced features
Groundwork for future workload testing capabilities

3. Distributed Replay basic concept
QA / Production
Test
System change
Trace File
Capture
Replay
(before)
Replay
(after)
Comparison Reports

4. Distributed Replay data & workflow
Batch Request
Preprocess 1
Batch Request
Trace File
IR file
IR file
IR file
IR file
IR file
Batch Request
User
Controller …
SQL Server
Replay 2
Batch Request
Multiple Replay Clients

5. Distributed Replay Concepts
Connect time: time delta between trace start and login is established
Think time: time delta between two events on the same connection

6. Preprocess & Replay Steps
What Happens During Preprocess:
Sort the events in ascending order of EventSequence
Trim away events and columns not used for replay
Generate an intermediate file
Goal: preprocess the trace once, and intermediate file can be replayed with different options
What Happens During Replay:
User specified the replay options, including which clients to use
Shred the intermediate file into chunks in a load-balanced fashion
Dispatch the file chunks to the clients
Two replay modes, stress and synchronization
Under stress mode, each client sends request independently
Under sync mode, client needs to coordinate with controller to know when a specific event can be released (this is optimized so it is not done for every single event)

7. Preprocess Options
IncSystemSession: Whether system session events are filtered out
MaxIdleTime: cap max idle time between events

8. Replay options for sequence control
Synchronization Mode
Stress Mode
StressScaleGranularity = SPID
StressScaleGranularity = Connection
Submit order
Event submit ordering across SPIDs
Event submit ordering within SPIDS
Event submit ordering within connections
Submit timing
Submit time synchronization
ConnectTimeScale (0%–100%)
ThinkTimeScale (0%–100%)
UseConnectionPooling (Yes | No)
When to use
High-fidelity replay mode, such as functional runs
Use 100% connect time scale and 100% think time scale for performance runs.
Use SPID granularity and reduce connect time scale and think time scale for moderate-stress runs.
Use Connection granularity and reduce connect time scale and think time scale for high-stress runs. 1 2 3

9. Synchronization Mode Events submitted in order across SPIDS
Emulate original event submit time:
Capture with original think time = 5s
If replay is faster; think time is increased
If replay is slower; think time is decreased
If replay is slower; think time is decreased

10. Stress Mode (SPID Granularity)
Replay:
StressScaleGranularity = SPID
ConnectTimeScale = 10%
ThinkTimeScale = 50%
Capture

11. Stress Mode (Connection Granularity)
Replay:
StressScaleGranularity = Connection
ConnectTimeScale = 10%
ThinkTimeScale = 50%
Capture

12. Other Replay Features (1)
Added type support for: sql_variant, money, smallmoney
Healthmon for deadlock detection:

13. Other Replay Features (2)
Automatically manages database context
Avoid DB mismatch between captured trace and current DB context – DR will issue a “USE DATABASE...” command if discrepancy is detected between current DB context and DB Name column in intermediate file during replay Configurable query timeout
Result trace collection
Execution success/failure
Execution elapsed time (microsec)
(On/Off) # of rows in result sets
(On/Off) result set contents
Supported SQL Server versions:
Input Trace File Version
Target SQL Server
SQL Server 2005
SQL Server 2008 / 2008 R2 / 2012
SQL Server 2008
SQL Server 2008 R2
SQL Server 2008 R2 / 2012
SQL Server 2012
SQL server 2012

14. Performance & scalability
40 playbacks tested internally:
Most run equally fast compared to SQL Profiler
Some run 3x – 10x faster than SQL Profiler
DReplay can scale-out when needed, SQL Profiler has no option
2 TAP trials during CTP:
Largest trace replayed: 100GB
Throughput achieved using 4 clients: 3000 batch requests/sec

15. Application compatibility testing
More thorough functional and performance testing
Detect potential upgrade issues not covered by Upgrade Advisor:
Test ad-hoc T-SQL embedded in application
Test actual T-SQL execution, not just syntactical checks
Test security configuration
May include OS level security settings
Detect changes in query plan, duration and results
Detects use of undocumented features/objects
Very rare but possible: identify changes that break or alter query behavior but is not documented (yet)
Not required for all applications but highly recommended for
Missions/business critical applications
Complex applications
Application where queries are mostly client-side, middle-tier or dynamic

16. Application compatibility Testing
QA / Production
Test
Database Upgrade
Trace File
Capture
Replay
(before)
Replay
(after)
Comparison Reports

17. SQL Server Upgrade Assistant V2
Leverages Profiler for SQL Trace capture
Leverages Distributed Replay to replay captured workload in trace file
Enhanced reporting capabilities on top of SSUA V1
Enhanced user interface

18. Application compatibility testing
Upgrade Assistant for SQL Server V2.0
powered by SQL Server 2012 Distributed Replay

19. Summary Key to a successful upgrade is planning & testing
Tools are intended to simplify and expedite execution, not to replace proper planning
Level of pre-upgrade validation/testing is typically proportionate to business criticality
There is a wealth of resources available
Feedback through Microsoft Connect will drive improvements in product and upgrade process/tools
We are working on plans for more automation for pre-upgrade validation

20. Resources Distributed Replay Upgrading to SQL Server 2012
Upgrading to SQL Server 2012
Upgrade Advisor
Application compatibility testing with Upgrade Assistant
Product feedback

21. Further. Forward. Faster.
Learn more Visit the Microsoft Virtual Academy Free technical SQL Server training courses
Get more Download SQL Server 2012 Trial Software 180-day evaluation of SQL Server 2012
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