Post on 01-Dec-2014
description
MONGODB FOR MULTI-DIMENSIONSPATIAL INDEXING
DECEMBER 2012
@nknize+Nicholas Knize
Thermopylae Sciences & Technology – Who are we?
• Mixed Government (70%) and Commercial (30%) contracting company w/ ~150 employees
• Core customers: – SOUTHCOM, Intel & Security Command, Army Intel Sector, DOI– LVMS, Select Energy Oil & Gas, OSU, Cleveland Cavaliers, and STL Rams
• #1 Google Enterprise partner for Federal and partner w/ imagery providers (GeoEye / Digital Globe)
• FOSS4G contributor and 10gen Enterprise partner
WHO ARE THESE GUYS?
ACCOMPLISHING THE IMPOSSIBLE
ENTERPRISEPARTNER
“The 3D UDOP allows near real time visibility of all SOUTHCOM Directorates information in one location…this capability allows for unprecedented situational awareness and information sharing”
-Gen. Doug Frasier
TST PRODUCTS
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COMMERCIAL CUSTOMERS
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Commercial Examples
ClevelandCavaliers
USGIF Las VegasMotor Speedway
BaltimoreGrand Prix
iSpatial framework serves millions of mobile devices
1. iSpatial provides web-based interface for Multi-INT visualization and collaborations2. Map/Reduce provides spatial statistic processing (spatial regression) and heuristics 3. Modified MongoDB provides storing and indexing multi-dimension spatial data at scale
TST ARCHITECTURE
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iSpatial – UI/Visualization
Hadoop M/R – Processing / Analysis
MongoDB – Spatial Data Management @ Scale
1 2
3
What the…..HOW MUCH DATA?!?
• “Swimming in sensors drowning in data”– What size data tsunami are we talking about?
• “Fix and Finish are meaningless until FIND is accomplished”– A “Big Data” Spatial Search Problem
THAT’S A LOT OF DATA….
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Sensor Type Resolution Data Bandwidth TB/Hr
FMV 640 x 480 (Std Def)1920 x 1080 (HD)
HD: 16bit x 3 bands @ 30fps ~1Gbps
~0.45 TB
WAMI Constant Hawk = 96 MpxGorgon Stare = 460 MpxArgus = 1.8 Gpx
GS @ 16bit x 3 bands @ 2fps ~15.3Gps
Argus @ 16bit x 3 bands @ 12fps ~345.6Gps
~6.89 TB
~155 TB
Satellite NITF / JP2 resolutions32K x 32K432K x 216K
32K x 32K @ 8bit x 3 bands @ 1frame/5mins ~27Gps
~12.15 TB
• Horizontally scalable – Large volume / elastic
• Vertically scalable – Heterogeneous data types (“Data Stack”)
• Smartly Distributed – Reduce the distance bits must travel
• Fault Tolerant – Replication Strategy and Consistency model
• High Availability – Node recovery
• Fast – Reads or writes (can’t always have both)
BIG DATA STORAGE CHARACTERISTICS
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Desired Data Store Characteristic for ‘Big Data’
• Cassandra– Nice Bring Your Own Index (BYOI) design– … but Java, Java, Java… Memory management can be a maintenance issue– Adding new nodes can be a pain (Token Changes, nodetool)– Key-Value store…good for simple data models
• Hbase– Nice BigTable model– Key-Value store…good for simple data models– Lots of Java JNI (primarily based on std:hashmap of std:hashmap)
• CouchDB– Provides some GeoSpatial functionality (Currently being rewritten)– HEAVILY dependent on Map-Reduce model (complicated design)– Erlang based – poor multi-threaded heap management
NOSQL OPTIONS
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Subset of Evaluated NoSQL Options
Why MongoDB for Thermopylae?• Documents based on JSON – A GEOJSON match made in heaven! (OGC)
• C++ - No Garbage Collection Overhead! Efficient memory management design reduces disk swapping and paging
• Disk storage is memory mapped, enabling fast swapping when necessary
• Built in auto-failover with replica sets and fast recovery with journaling
• Tunable Consistency – Consistency defined at application layer
• Schema Flexible – friendly properties of SQL enable easy port
• Provided initial spatial indexing support – Point based limited!WHY TST <3’S MONGODB
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MONGODB SPATIAL INDEXER
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... The Spatial Indexer wasn’t quite right
• MongoDB (like nearly all relational DBs) uses a b-Tree – Data structure for storing sorted data in log time– Great for indexing numerical and text documents (1D attribute data)– Cannot store multi-dimension (>2D) data – NOT COMPLEX GEOMETRY
FRIENDLY
DIMENSIONALITY REDUCTION
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How does MongoDB solve the dimensionality problem?
• Space Filling (Z) Curve – A continuous line that
intersects every point in a two-dimensional plane
• Use Geohash to represent lat/lon values– Interleave the bits of a
lat/long pair– Base32 encode the result
GEOHASH BTREE ISSUES
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• Neighbors aren’t so close!– Neighboring points on the
Geoid may end up on opposite ends of the plane
– Impacts search efficiency
• What about Geometry?– Doesn’t support > 2D– Mongo uses Multi-
Location documents which really just indexes multiple points that link back to a single document
Issues with the Geohash b-Tree approach
Sort Order and Multi-Dimension…a nightmare(3D / 4D Hilbert Scanning Order)
GEO-SHARDING ALTERNATIVE
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Case 3:
Case 4:
Multi-Location Document (aka. Polygon) Search Polygon
Case 1:
Case 2:
Success!
Success!
Fail!
Fail!
Mongo Multi-location Document Clipping Issues($within search doesn’t always work w/ multi-location)
MULTI-LOCATION CLIPPING
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• Constrain the system to single point searches– Multi-dimension support will be exponentially complex (won’t scale)
• Interpolate points along the edge of the shape– Multi-dimension support will be exponentially complex (won’t scale)
• Customize the spatial indexer– Selected approach
SOLUTIONS TO GEOHASH PROBLEM
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Potential Solutions
CUSTOM TUNED SPATIAL INDEXER
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Thermopylae Custom Tuned MongoDB for Geo
TST Leverage’s Kriegel’s 1996 Research in R* Trees• R-Trees organize any-dimensional data by representing
the data as a minimum bounding box. • Each node bounds it’s children. A node can have many
objects in it (max: m min: ceil(m/2) )• Splits and merges optimized by minimizing overlaps• The leaves point to the actual objects (stored on disk
probably)• Height balanced – search is always O(log n)
Spatial Indexing at Scale with R-Trees
RTREE THEORY
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Spatial data represented as minimum bounding rectangles (2-dimension), cubes (3-dimension), hexadecant (4-dimension)
Index represented as: <I, DiskLoc> where:
I = (I0, I1, … In) : n = number of dimensionsEach I is a set in the form of [min,max] describing MBR range along a
dimension
R*-Tree Spatial Index Example• Sample insertion result for 4th order
tree• Objectives:
1. Minimize area2. Minimize overlaps3. Minimize margins4. Maximize inner node utilization
a b cd e f g h i j k l
m n o p
R*-TREE INDEX OBJECTIVES
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Insert
• Similar to insertion into B+-tree but may insert into any leaf; leaf splits in case capacity exceeded.– Which leaf to insert into?– How to split a node?
R*-TREE INSERT EXAMPLE
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Insert—Leaf Selection
• Follow a path from root to leaf.• At each node move into subtree whose MBR area
increases least with addition of new rectangle.
mn
o p
Modified from Dr. Sahni (UoF Advanced Data Structures)
Insert—Leaf Selection
• Insert into m.
m
Modified from Dr. Sahni (UoF Advanced Data Structures)
Insert—Leaf Selection
• Insert into n.
n
Modified from Dr. Sahni (UoF Advanced Data Structures)
Insert—Leaf Selection
• Insert into o.
o
Modified from Dr. Sahni (UoF Advanced Data Structures)
Insert—Leaf Selection
• Insert into p.
p
Modified from Dr. Sahni (UoF Advanced Data Structures)
mn
o p
aa
a
x
a b cd e f g h i j k l
m n o p
Query• Start at root• Find all overlapping MBRs• Search subtrees recursively
Modified from Dr. Sahni (UoF Advanced Data Structures)
Query
• Search m.
mn
o p
a
a
x x
a b cd e f g h i j k l
m n o p
a
aa
b
cd
e
g
Modified from Dr. Sahni (UoF Advanced Data Structures)
R*-Tree Leverages B-Tree Base Data Structures (buckets)
R*-TREE MONGODB IMPLEMENTATION
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Spatial Index Architecture, Organization, & Performance
MBRKeyNode(s)
BucketHeader
MBRHeader
…
Dimensions Num Buckets Tree Height Read Time
3 3,448,276 3 190 ms
5 50,76,143 3 275 ms
100 90,909,091 8 ~4.9 sec
1B Polygon Read Performance (worst case O(n))
SPATIAL INDEX ARCH & ORG
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Geo-Sharding – (in work)Scalable Distributed R* Tree (SD-r*Tree)
“Balanced” binary tree, with nodes distributed on a set of servers:
• Each internal node has exactly two children
• Each leaf node stores a subset of the indexed dataset
• At each node, the height of the subtrees differ by at most one
• mongos “routing” node maintains binary tree
GEO-SHARDING
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d0 d1
r1d0Data Node Spatial
Coverage
a a
b
c
cb d0
r1
a
b
c
c
b
d2d1
ed
d
r2
e
SD-r*Tree Data Structure Illustration
• di = Data Node (Chunk)• ri = Coverage Node
Leveraged work from Litwin, Mouza, Rigaux 2007
SD-r*Tree DATA STRUCTURE
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SD-r*Tree Structure Distribution
d0
r1
a
b
c
c
b
d2d1
ed
d
r2
e
r2
d1 d2
d0
r1
GeoShard 2 GeoShard 3
GeoShard 1
mongos
SD-r*TREE STRUCTURE DISTRIBUTION
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Beyond 4-Dimensions - X-Tree(Berchtold, Keim, Kriegel – 1996)
Normal Internal Nodes Supernodes Data Nodes
• Avoid MBR overlaps – more overlaps approaches worst case O(n) read
• Avoid node splits (main cause for high overlap)
• Introduce new node structure: Supernodes – Large Directory nodes of variable size
BEYOND 4-DIMENSIONS
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X-TREE PERFORMANCE
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X-Tree Performance Results(Berchtold, Keim, Kriegel – 1996)
T-Sciences Custom Tuned Spatial Indexer
• Optimized Spatial Search – Finds intersecting MBR and recurses into those nodes
• Optimized Spatial Inserts – Uses the Hilbert Value of MBR centroid to guide search – 28% reduction in number of nodes touched
• Optimize Deletes – Leverages R* split/merge approach for rebalancing tree when nodes become over/under-full
• Low maintenance – Leverages MongoDB’s automatic data compaction and partitioning
CONCLUSION
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Example: Mosaicked Video with KLV Footprints
SLIDESHOW HEADER
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• Rip through KLV Metadata
• Index frame footprints, and annotations as MBR into X(R*)-Tree
• Leverage Geo-Sharding for spatially relevant scale
Example Use Case – OSINT (Foursquare Data)
• Sample Foursquare data set mashed with Government Intel Data (poly reports)
• 100 million Geo Document test (3D points and polys)
• 4 server replica set
• ~350ms query response
• ~300% improvement over PostGIS
EXAMPLE
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Community Support
• Thermopylae plans to open source– http://github.com/thermopylae
• TST working with 10gen to offer as a spatial extension
• Active developer collaboration– IRC: #mongodb freenode.net
FIND US
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THANK YOUQuestions?
Nicholas Knizenknize@t-sciences.com
THANK YOU
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Backup
Key Customers - Government• US Dept of State Bureau of Diplomatic Security
– Build and support 30 TB Google Earth Globe with multi-terabytes of individual globes sent to embassies throughout the world. Integrated Google Earth and iSpatial framework.
• US Army Intelligence Security Command– Provide expertise in managing technology integration – prime
contractor providing operations, intelligence, and IT support worldwide. Partners include IBM, Lockheed Martin, Google, MIT, Carnegie Mellon. Integrated Google Earth and iSpatial framework.
• US Southern Command– Coordinate Intelligence management systems spatial data collection,
indexing, and distribution. Integrated Google Earth, iSpatial, and iHarvest.
– Index large volume imagery and expose it for different services (Air Force, Navy, Army, Marines, Coast Guard)
GOVERNMENT CUSTOMERS
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COMMERCIAL CUSTOMERS
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Key Customers - Commercial
ClevelandCavaliers
USGIF Las VegasMotor Speedway
BaltimoreGrand Prix
iSpatial framework serves millions of mobile devices
• Expose and manage Multi-INT enterprise data in a geo-temporal user defined environment
• Provide a flexible and scalable spatial data infrastructure (SDI) for Multi-INT data access and analysis
• Spatially referenced data visualization on 3D globe & 2D maps• Access real/near real-time data feeds from forward deployed
devices • Enable real-time information sharing and mission collaboration
ISPATIAL OVERVIEW
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