Le slide di Massimo Brignoli presentate a Codemotion Roma 2014

1. Time Series Data in MongoDB
Senior Solutions Architect, MongoDB Inc.
Massimo Brignoli
#mongodb

2. Agenda
• What is time series data?
• Schema design considerations
• Broader use case: operational intelligence
• MMS Monitoring schema design
• Thinking ahead
• Questions

3. What is time series data?

4. Time Series Data is Everywhere
• Financial markets pricing (stock ticks)
• Sensors (temperature, pressure, proximity)
• Industrial fleets (location, velocity, operational)
• Social networks (status updates)
• Mobile devices (calls, texts)
• Systems (server logs, application logs)

5. Time Series Data at a Higher Level
• Widely applicable data model
• Applies to several different “data use cases”
• Various schema and modeling options
• Application requirements drive schema design

6. Time Series Data Considerations
• Resolution of raw events
• Resolution needed to support
– Applications
– Analysis
– Reporting
• Data retention policies
– Data ages out
– Retention

7. Schema Design
Considerations

8. Designing For Writing and Reading
• Document per event
• Document per minute (average)
• Document per minute (second)
• Document per hour

9. Document Per Event
{
server: “server1”,
load: 92,
ts: ISODate("2013-10-16T22:07:38.000-0500")
}
• Relational-centric approach
• Insert-driven workload
• Aggregations computed at application-level

10. Document Per Minute (Average)
{
server: “server1”,
load_num: 92,
load_sum: 4500,
ts: ISODate("2013-10-16T22:07:00.000-0500")
}
• Pre-aggregate to compute average per minute more easily
• Update-driven workload
• Resolution at the minute-level

11. Document Per Minute (By Second)
{
server: “server1”,
load: { 0: 15, 1: 20, …, 58: 45, 59: 40 }
ts: ISODate("2013-10-16T22:07:00.000-0500")
}
• Store per-second data at the minute level
• Update-driven workload
• Pre-allocate structure to avoid document moves

12. Document Per Hour (By Second)
{
server: “server1”,
load: { 0: 15, 1: 20, …, 3598: 45, 3599: 40 }
ts: ISODate("2013-10-16T22:00:00.000-0500")
}
• Store per-second data at the hourly level
• Update-driven workload
• Pre-allocate structure to avoid document moves
• Updating last second requires 3599 steps

13. Document Per Hour (By Second)
{
server: “server1”,
load: {
0: {0: 15, …, 59: 45},
….
59: {0: 25, …, 59: 75}
ts: ISODate("2013-10-16T22:00:00.000-0500")
}
• Store per-second data at the hourly level with nesting
• Update-driven workload
• Pre-allocate structure to avoid document moves
• Updating last second requires 59+59 steps

14. Characterzing Write Differences
• Example: data generated every second
• Capturing data per minute requires:
– Document per event: 60 writes
– Document per minute: 1 write, 59 updates
• Transition from insert driven to update driven
– Individual writes are smaller
– Performance and concurrency benefits

15. Characterizing Read Differences
• Example: data generated every second
• Reading data for a single hour requires:
– Document per event: 3600 reads
– Document per minute: 60 reads
• Read performance is greatly improved
– Optimal with tuned block sizes and read ahead
– Fewer disk seeks

16. MMS Monitoring Schema
Design

17. MMS Monitoring
• MongoDB Management System Monitoring
• Available in two flavors
– Free cloud-hosted monitoring
– On-premise with MongoDB Enterprise
• Monitor single node, replica set, or sharded cluster
deployments
• Metric dashboards and custom alert triggers

18. MMS Monitoring

19. MMS Monitoring

20. MMS Application Requirements
Resolution defines granularity of
stored data
Range controls the retention
policy, e.g. after 24 hours only 5-
minute resolution
Display dictates the stored pre-
aggregations, e.g. total and count

21. Monitoring Schema Design
• Per-minute documentmodel
• Documentsstore individual metrics and counts
• Supports“total” and “avg/sec”display
{
timestamp_minute: ISODate(“2013-10-10T23:06:00.000Z”),
num_samples: 58,
total_samples: 108000000,
type: “memory_used”,
values: {
0: 999999,
…
59: 1800000
}
}

22. Monitoring Data Updates
• Single update required to add new data and
increment associated counts
db.metrics.update(
{
timestamp_minute: ISODate("2013-10-10T23:06:00.000Z"),
type: “memory_used”
},
{
{$set: {“values.59”: 2000000 }},
{$inc: {num_samples: 1, total_samples: 2000000 }}
}
)

23. Monitoring Data Management
• Data stored at different granularity levels for read
performance
• Collections are organized into specific intervals
• Retention is managed by simply dropping
collections as they age out
• Document structure is pre-created to maximize write
performance

24. Use Case: Operational
Intelligence

25. What is Operational Intelligence
• Storing log data
– Capturing application and/or server generated events
• Hierarchical aggregation
– Rolling approach to generate rollups
– e.g. hourly > daily > weekly > monthly
• Pre-aggregated reports
– Processing data to generate reporting from raw events

26. Storing Log Data
{
_id: ObjectId('4f442120eb03305789000000'),
host: "127.0.0.1",
user: 'frank',
time: ISODate("2000-10-10T20:55:36Z"),
path: "/apache_pb.gif",
request: "GET /apache_pb.gif HTTP/1.0",
status: 200,
response_size: 2326,
referrer: “http://www.example.com/start.html",
user_agent: "Mozilla/4.08 [en] (Win98; I ;Nav)"
}
127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET /apache_pb.gif HTTP/1.0" 200 2326
"[http://www.example.com/start.html](http://www.example.com/start.html)" "Mozilla/4.08 [en]
(Win98; I ;Nav)”

27. Pre-Aggregation
• Analytics across raw events can involve many reads
• Alternative schemas can improve read and write
performance
• Data can be organized into more coarse buckets
• Transition from insert-driven to update-driven
workloads

28. Pre-Aggregated Log Data
{
timestamp_minute: ISODate("2000-10-10T20:55:00Z"),
resource: "/index.html",
page_views: {
0: 50,
…
59: 250
}
}
• Leverage time-seriesstyle bucketing
• Trackindividual metrics (ex. page views)
• Improve performancefor reads/writes
• Minimal processingoverhead

29. Hierarchical Aggregation
• Analytical approach as opposed to schema
approach
– Leverage built-inAggregation Framework or MapReduce
• Execute multiple tasks sequentially to aggregate at
varying levels
• Raw events  Hourly  Weekly  Monthly
• Rolling approach distributes the aggregation
workload

30. Thinking Ahead

31. Before You Start
• What are the application requirements?
• Is pre-aggregation useful for your application?
• What are your retention and age-out policies?
• What are the gotchas?
– Pre-create document structure to avoid fragmentation and
performance problems
– Organize your data for growth – time series data grows
fast!

32. Down The Road
• Scale-out considerations
– Vertical vs. horizontal (with sharding)
• Understanding the data
– Aggregation
– Analytics
– Reporting
• Deeper data analysis
– Patterns
– Predictions

33. Scaling Time Series Data in
MongoDB
• Vertical growth
– Larger instances with more CPU and memory
– Increased storage capacity
• Horizontal growth
– Partitioning data across many machines
– Dividing and distributing the workload

34. Time Series Sharding
Considerations
• What are the application requirements?
– Primarily collecting data
– Primarily reporting data
– Both
• Map those back to
– Write performance needs
– Read/write query distribution
– Collection organization (see MMS Monitoring)
• Example: {metric name, coarse timestamp}

35. Aggregates, Analytics, Reporting
• Aggregation Framework can be used for analysis
– Does it work with the chosen schema design?
– What sorts of aggregations are needed?
• Reporting can be done on predictable, rolling basis
– See “HierarchicalAggregation”
• Consider secondary reads for analytical operations
– Minimize load on production primaries

36. Deeper Data Analysis
• Leverage MongoDB-Hadoop connector
– Bi-directional support for reading/writing
– Works with online and offline data (e.g. backup files)
• Compute using MapReduce
– Patterns
– Recommendations
– Etc.
• Explore data
– Pig
– Hive

37. Questions?

38. Resources
• Schema Design for Time Series Data in MongoDB
http://blog.mongodb.org/post/65517193370/schema-design-for-time-series-
data-in-mongodb
• Operational Intelligence Use Case
http://docs.mongodb.org/ecosystem/use-cases/#operational-intelligence
• Data Modeling in MongoDB
http://docs.mongodb.org/manual/data-modeling/
• Schema Design (webinar)
http://www.mongodb.com/events/webinar/schema-design-oct2013