I need the data and I need it 1ms ago!

OpenSplice DDS
Delivering Performance, Openness, and Freedom

I Need Market Data
Angelo Corsaro, Ph.D.
Chief Technology Officer
OMG DDS SIG Co-Chair
angelo.corsaro@prismtech.com

and I need it 1ms Ago!

OpenSplice DDS

Challenges

Financial Firms
Trends
‣ Direct connection to exchanges is increasingly chosen
over data aggregators to reduce trading latency
‣ Market data is growing steadily
‣ Milliseconds speedup over competitors can be worth
millions of dollars
Challenges
‣ Process several hundreds-of-thousands of messages,
quickly approaching millions messages, per second
‣ Minimize latency and jitter, while maintaining the
system stability and reliability

Deployed middleware solutions were not designed to
address these challenges!
© 2009, PrismTech. All Rights Reserved

Exchanges
Trends
‣ More and more firms connecting directly
‣ Increasing number of sources providing the same quotes
‣ Competitive advantage obtained by reducing latency on data
feeds
Challenges
‣ Ensuring fairness of data distribution
‣ Minimizing latency
‣ Scaling with the number of destinations

Deployed middleware solutions were not
designed to address these challenges!


OPRA Predictions
OPRA Market Data Rates Forecasts Trends
2000000

Msgs/sec 1807000
‣ One order of magnitude
growth on market data
from 2005 to 2008
1500000

‣ OPRA message rates
predicted to reach ~2M
1000000 msgs/sec by early 2009
701000
‣ Traffic bursts predicted to
further increase by 20%
500000 359000

Challenges
‣ Can your messaging
190000
Jan 6, 2009
Jan 8, 2008
88000 Jan 9, 2007
0
May 16, 2006 infrastructure keep-up
Jan 13, 2005
with this trend?


Trading with Pareto
‣ Usually 20% of the trades
provides 80% of the gains
Msgs/sec
‣ Under overload condition
how can you ensure you
keep trading at least 20%
of your target?
Vilfredo Pareto, 1848-1923
‣ How can you ensure that
you keep trading the the
Average
right 20% of data?

System Message Rate
Incoming Message Rate

Time


OpenSplice DDS

The Data Distribution Service
for Real-Time Systems (DDS)

Addressing Data Distribution Challenges
DDS is standard designed to address the data-distribution challenges across
The OMG DDS Standard a wide class of Defense and Aerospace Applications
‣ Introduced in 2004 to address the Data
Distribution challenges faced by a wide
class of Defense and Aerospace
Applications
‣ Key requirement for the standard were its
ability to deliver very high performance while
seamlessly scaling from embedded to ultra-
large-scale deployments
‣ Today recommended by key administration
worldwide and widely adopted across
several different application domains, such
as, Automated Trading, Simulations, SCADA,
Telemetry, etc.


The OMG Data Distribution Service (DDS)

DDS v1.2 API Standard
‣ Language Independent, OS and HW architecture Application

independent Object/Relational Mapping

‣ DCPS. Standard API for Data-Centric, Topic- Data Local Reconstruction Layer (DLRL)

Based, Real-Time Publish/Subscribe
Content
‣
Ownership Durability
DLRL. Standard API for creating Object Views out Subscription

of collection of Topics Minimum Proﬁle

Data Centric Publish/Subscribe (DCPS)
DDSI/RTPS v2.1 Wire Protocol Standard
‣ Standard wire protocol allowing interoperability
Real-Time Publish/Subscribe Protocol

DDS Interoperability Wire Protocol
between different implementations of the DDS
standard UDP/IP

‣ Interoperability demonstrated among key DDS
vendors in March 2009

Scope of Standardization
AMQP OMG DDS
Application
Application
Object/Relational Mapping

Data Local Reconstruction Layer (DLRL)

DDS v1.2
Content
Subscription
API (?) Minimum Proﬁle


DDSI v2.1
AMQP v0.10

Advanced Message Queuing Protocol Real-Time Publish/Subscribe Protocol

Interoperability Wire Protocol DDS Interoperability Wire Protocol

(TCP, SCTP, UDP)/IP UDP/IP


AMQP OMG DDS
Application
Application


DDS v1.2
Content
Subscription


DDSI v2.1
AMQP v0.10

Wire Protocol Standard



AMQP OMG DDS
Application
Application


DDS v1.2
Content
Subscription
Pub/Sub Standard API


DDSI v2.1
AMQP v0.10




AMQP OMG DDS
Application
Application
Object/Relational Mapping Object Relational Mapping
Data Local Reconstruction Layer (DLRL) Standard API

DDS v1.2
Content
Subscription
Pub/Sub Standard API


DDSI v2.1
AMQP v0.10




Architectural Style

AMQP OMG DDS
Subscriber Subscriber
Publisher Publisher

Broker Broker

Publisher
Broker Subscriber
Publisher
Broker Subscriber

Broker
Broker

Publisher Publisher
Subscriber Subscriber


Key Differences in Summary
DDS AMQP
‣ Peer-to-Peer Communication ‣ Brokered Communication
Architecture Architecture

‣ Wire Protocol + API Standard ‣ Wire Protocol Standard
‣ Interoperability across DDS implementations ‣ Interoperability across AMQP
implementations
‣ Application Portability across DDS
Implementation

‣ Content-Based Filtering/Quering ‣ Header Based Routing

‣ Designed bottom-up for maximum ‣ Not geared for High-Performance
performance and determinism


OpenSplice DDS

DDS and Open Source

OpenSplice DDS
‣ Product reorganized into Editions
‣ Community Edition
Enterprise Ed.
‣ Compact Edition
‣ Professional Edition
‣ Enterprise Edition Professional Ed.

Proprietary Information - Distribution without Expressed Written Permission is Prohibited.
‣ Product Editions provide a a growing set of
Enterprise Ed. Compact Ed.
functionality to address the needs of increasingly
more sophisticated users
‣ The Community Edition is Open Source Community Ed.

‣ Compact, Enterprise and Professional Edition are
available only through Commercial Subscriptions


Community Edition
Features Licensing
‣ OMG DDS v1.2 DCPS ‣ LGPLv3
‣ Minimum Profile
‣ Content Subscription Profile Application
‣ Durability Profile

‣ Ownership Profile Content

DDS v1.2
Subscription

‣ Networking Minimum Proﬁle

‣ DDSI v2.1 Implementation Real-Time Pub/Sub (DCPS)

‣ Real-Time Networking Implementation

DDSI v2.1
Interoperable Wire Protocol
Real-Time Networking
(DDSI)

Networking Technology

UDP/IP

Open Source LGPL Licensed Edition -- The Best Way to Get Started with DDS

Performance on Commodity HW
Throughput -./0/1/23' 456/'
Latency
#+(+%++' &&++%++'

$+(+%++' "*(%)+' ")(%&!' ""&%,&'&+++%++' Inter-Node Latency
!"#$%&#'

‣ 60 usec
"!+%++'
)"#%*)' "++%++'
)$,%$*'
!+(+%++'
)++%++'
Inter-Core Read-Latency
&'$($)$*+%

*!#%,&'

‣ 2 usec

!"#$%
,+(+%++' *++%++'
()(!%(*'

#++%++'
(+(+%++' &")&%+)' Inter-Core Latency
‣ <10 usec
$&"%,,'
$++%++'
&!(,%!)'

&+(+%++'
),,%$#' !++%++'
,*+%&)'
!,*%))'
,($%!+' (("%!"'
&&)%*$' $"%"$' ,+%($' ,++%++' HW:
(+%++'
)' &#' ,(' #!' &()' ($#' $&(' &+(!' (+!)' !+"#'
‣ Dell blade-server
!*$$,(*%-./*%
‣ Dual-core, Dual-CPU, AMD Opteron 2.4 Ghz
Test Scenario OS
‣ Linux 2.6.21-1.3194.fc7
‣ Single Threaded Application (multi-threaded networking service) Network
‣ 8192 bit message batches ‣ Gigabit Ethernet cards
‣ Dell PowerConnect 5324 switch

OpenSplice DDS Adoption
Defense
‣ Combat Management Systems
‣ Tactical Systems
‣ Drones (land/air)
‣ Communication Systems

‣ Radar Processing
‣ Submarine Systems
‣ Future Combat Systems
SCADA/Utilities
‣ Industrial Automation
‣ Power Grids (Smart Grids)
‣ Complex Telemetry (e.g. NASA Rocket Launch System)

OpenSplice DDS Adoption
Transportation
‣ Air Traffic Management/Control
‣ Metropolitan Traffic Management
‣ Underground Metropolitan Transportation

Financial Services
‣ Automated Trading
‣ Risk Management
‣ Option Trading


Some OpenSplice DDS Users

!"#$%&'()('*+'##,-+.+/($$,012"0

Experti
réalisée par Bernard M

OpenSplice DDS

Understanding DDS

As Simple as it Gets
‣ DDS is based around the concept
of a fully distributed Global Data
Space (GDS)
Brokers

Global Data Space

DDS


Space (GDS)
‣ Publishers and Subscribers can Brokers
join and leave the GDS at any time
Global Data Space

DDS


Publisher Subscriber
Space (GDS)
Subscriber
Publisher
Global Data Space


DDS


Space (GDS)
Subscriber
‣ Publishers and Subscribers Publisher
Global Data Space
express their intent to produce/
consume specific type of data,
e.g., Topics

DDS


Space (GDS)
Subscriber
‣ Publishers and Subscribers Publisher Global Data Space
express their intent to produce/
consume specific type of data,
e.g., Topics
Subscriber
‣ Data flows from Publisher to Publisher

Subscribers DDS


OpenSplice DDS

Deﬁning Data

DDS Topics
{Circle, Square, Triangle}
Topic
‣ Unit of information exchanged between
Publisher and Subscribers.
‣ An association between a unique name, a
type and a QoS setting {ShapeType} {...}

Topic Type.
struct ShapeType {
‣ Type describing the data associated with one long x;
or more Topics long y;
‣ A Topic type can have a key represented by an long shapesize;
string color;
arbitrary number of attributes };
‣ Expressed in IDL (or XML) #pragma keylist ShapeType color


DDS Topics

Circle

struct ShapeType {
long x;
long y;
long shapesize; Topic QoS
string color;
};
#pragma keylist ShapeType color


DDS Topics

Triangle

struct ShapeType {
long x;
long y;
long shapesize; Topic QoS
string color;
};


DDS Topic Instances and Samples
Topic Instances
‣ Each key value identifies a unique Topic Instance,
‣ Topic’s instance lifetime can be explicitly
managed in DDS

Topic Samples
‣ The values assumed by a Topic Instance
over time are referred as Instance Sample
struct ShapeType {
long x;
long y;
long shapesize;
string color;
};

Topic/Instances/Samples Recap.
Topics Instances

Samples

ti tj tnow time

Content Filtering
X0 X1
X0 <= X <= X1
‣ DDS allows to specify content-
filtered Topics for which a subset
of SQL92 is used to express the
filter condition
Y0
‣ Content filters can be applied on
the entire content of the Topic Type Y0 <= Y <= Y1

‣ Content filters are applied by DDS
Y1
each time a new sample is
produced/delivered


Local Queries
‣ Subscribed Topics can be seen locally as “Tables”
‣ A subset of SQL92 can be used for performing queries on X0
multiple topics as well as natural joins
‣ Queries are Circle Topic
performed under Y0
color x y shapesize Y0
user control and red 57 62 50
provide a result that blue 90 85 50
Y0 <= Y <= Y1
depends on the yellow 30 25 50

current snapshot of SELECT * FROM ShapeType s
WHERE s.x > 25 AND s.y < 55 Y1
the system, e.g.,
samples currently color x y shapesize
available yellow 30 25 50


OpenSplice DDS

Anatomy of a DDS App.

Anatomy of a DDS Application

Topic
TopicTopic Circle)
(e.g.
Samples
Samples
Instances Samples
Instances
Instances
1 21 62
1 21 62
1 22 62
1 22 62
1 23 63
1 23 63
DataReader
DataReader
blue 21 62 80 blue 23 66 80 blue 27 70 80
2 20 61 2 19 60
DataReader
DataReader 2 20 61 2 19 60
orange 21 62 80 orange 21 62 80 DataWriter
DataWriter
DataReader
DataReader struct ShapeType {
3 25 70 3 25 71
25 3 25 74 3 26 77
3 26 77
DataWriter
DataWriter
long x; 3 25 70 3 25 71
25 3 25 74
long y; green 97 75 50 green 94 71 50
long shapesize;
string color;
};



Topic
TopicTopic Circle)
(e.g.
Samples
Samples
Instances Samples
Instances
Instances
1 21 62
1 21 62
1 22 62
1 22 62
1 23 63
1 23 63
DataReader
DataReader
blue 21 62 80 blue 23 66 80 blue 27 70 80
2 20 61 2 19 60
DataReader
DataReader 2 20 61 2 19 60
DataWriter
DataReader
3 25 70 3 25 71
25 3 25 74 3 26 77
3 26 77
DataWriter
DataWriter
long x; 3 25 70 3 25 71
25 3 25 74
long shapesize;
string color;
Arrows };
show
structural
relationship
s, not data-
ﬂows Partition



Topic
TopicTopic Circle)
(e.g.
Samples
Samples
Instances Samples
Instances
Instances
1 21 62
1 21 62
1 22 62
1 22 62
1 23 63
1 23 63
DataReader
DataReader
blue 21 62 80 blue 23 66 80 blue 27 70 80
2 20 61 2 19 60
DataReader
DataReader 2 20 61 2 19 60
DataWriter
DataReader
3 25 70 3 25 71
25 3 25 74 3 26 77
3 26 77
DataWriter
DataWriter
long x; 3 25 70 3 25 71
25 3 25 74
long shapesize;
string color;
Arrows };
show
structural
relationship
s, not data- Subscriber Publisher
ﬂows Partition

Domain Participant

Domain

OpenSplice DDS

From Shapes to Market Data

The Market Data Topic
Type Declaration Topic Instantiation

struct StockQuote {
char<4> symbol; // Create Topic with Default QoS
char<4> exchange; dds::Topic<StockQuote> topic(“stock_quote”);
char<64> name;
float quote; // Create Content Filtered Topic
dds::ContentFilteredTopic cfTopic =
}; topic.create_content_filtered(expr,
#pragma keylist StockQuote symbol params);

symbol name exchange quote
AAPL Apple Inc. NASD 165.37
GOOG Google Inc. NASD 663.97
MSFT Microsoft Corp. NASD 33.73


Filtering Market Data
Apple
164.0 Microsoft
40

161.5

30
MSFT > $35
159.0

20

AAPL < $157 |156.5
AAPL > $162 10

154.0
Untitled 1 Untitled 20 Untitled 39 Untitled 58 Untitled 77 Untitled 96

0
AAPL MSFT

‣ DDS continuous queries can be used for filtering the stream of data produced for a
specific stock symbol.


Writing Market Data
Creating a Writer
// Create Topic with Default QoS
dds::Topic<StockQuote> topic(“stock_quote”);

// Create a Writer with Default Qos
dds::Writer<StockQuote> writer(topic);


Writing Market Data
Creating a Writer


Writing Data

StockQuote quote = {
“AAPL”, “NASD”,
163.37, “Apple Inc.”
};

writer.write(quote);


Writing Market Data
Creating a Writer


Writing Data Fastest Way of Writing Data
163.37, “Apple Inc.”
163.37, “Apple Inc.” };
};
dds::InstanceWriter iwriter =
writer.write(quote); writer.register_instance(quote);
iwriter.write(quote);


OpenSplice DDS

Topic Used in next section.
Read vs. Take
struct Counter {
int cID;
int count;
};
#pragma keylist Counter cID

Reading Samples
‣ Read iterates over the
available sample instances
1 1 1 2 1 3 1 4
‣ Samples are not removed
2 1 2 2 2 3
from the local cache as
DataReader

3 4 3 5
result of a read
3 1 3 2 3 3
‣ Read samples can be read
Topic again, by accessing the
Samples Read Samples not Read cache with the proper
options (more later)
DataReader Cache


Reading Samples
‣ Read iterates over the
1 1 1 2 1 3 1 4
‣ Samples are not removed
2 1 2 2 2 3
from the local cache as
DataReader

3 1 3 2 3 3 3 4 3 5
result of a read
‣ Read samples can be read
Topic
again, by accessing the
Samples Read Samples not Read cache with the proper
options (more later)
DataReader Cache


Taking Samples
‣ Take iterates over the
1 1 1 2 1 3 1 4
‣ Taken Samples are
2 1 2 2 2 3
removed from the local
DataReader

3 4 3 5
cache as result of a take
3 1 3 2 3 3
‣
Topic

Samples not Taken

DataReader Cache


Taking Samples
1 2 1 3 1 4
2 2 2 3
DataReader

3 2 3 3 3 4 3 5

Topic

Samples not Taken

DataReader Cache


Taking Samples
1 3 1 4
2 3
DataReader

3 3 3 4 3 5

Topic

Samples not Taken

DataReader Cache


Reading Data
Creating a Reader

// Create a Reader with Default Qos
dds::Reader<StockQuote> reader(topic);


Reading Data
Creating a Reader


Reading Data

StockQuoteSeq data;
dds::SampleInfoSeq info;

reader.read(data, info);


Reading Data
Creating a Reader


Reading a Specific Instance
Reading Data
StockQuote quote;
quote.symbol = “APPL”;
StockQuoteSeq data; StockQuoteSeq data;
dds::SampleInfoSeq info; dds::SampleInfoSeq info;

reader.read(data, info); dds::InstanceReader ireader =
reader.instance(quote);
ireader.read(data, info);


Taking Data
Creating a Reader



Taking Data
Creating a Reader


Taking Data

StockQuoteSeq data;
dds::SampleInfoSeq info;

reader.take(data, info);


Taking Data
Creating a Reader


Taking a Specific Instance
Taking Data
StockQuote quote;
quote.symbol = “APPL”;
StockQuoteSeq data; StockQuoteSeq data;
dds::SampleInfoSeq info; dds::SampleInfoSeq info;

reader.take(data, info); dds::InstanceReader ireader =
reader.instance(quote);
ireader.take(data, info);


Sample, Instance and View States
History Depth = 2

‣ Along with data samples, DataReaders are provided
1 1
with state information allowing to detect relevant
2 2
transitions in the life-cycle of data as well as data
3 writers
DataReader

SampleInfo ‣ Sample State (READ | NOT_READ): Determines
wether a sample has already been read by this
1 1 1 2
DataReader or not.
2 2 2 3
‣ Instance State (ALIVE, NOT_ALIVE, DISPOSED).
3 1
Determines wether (1) writer exist for the specific
Samples instance, or (2) no matched writers are currently
Topic available, or (3) the instance has been disposed

DataReader Cache
‣ View State (NEW, NOT_NEW). Determines wether
this is the first sample of a new (or re-born) instance

Would you let me know...
DDS provides three main mechanism for exchanging information with the
application

‣ Polling. The application polls from time to time for new data or status changes.

The interval might depend on the kind of applications as well as data

‣ WaitSets. The application registers a WaitSet with DDS and waits (i.e. is
suspended) until one of the specified events has happened.

‣ Listeners. The application registers a listener with a specific DDS entity to be
notified when relevant events occur, such as state changes or


Reading with Waitsets
// Functor handling new data arrival 1
struct MarketDataHandler {
void operator()(MarketDataReader& reader);
};


};

// Create & Register Condition 2

MarketDataHandler functor;
dds::ReadCondition cond =
reader.create_read_condition(functor);
dds::WaitSet ws;
ws.attach(cond);


};


dds::WaitSet ws;
ws.attach(cond);

// Wait & Handle 3’
dds::ConditionVector cvec = ws.wait();
for (int i = 0; i < cvec.size(); ++i)
cvec[i].execute();


};


dds::WaitSet ws;
ws.attach(cond);

// Wait & Handle 3’ // Dispatch 3”
dds::ConditionVector cvec = ws.wait(); ws.dispatch();
for (int i = 0; i < cvec.size(); ++i)
cvec[i].execute();


Reading with Listeners
class MarketDataListener {
public:
void handle_data(MarketDataReader& reader);
};


Reading with Listeners
class MarketDataListener {
public:
void handle_data(MarketDataReader& reader);
};

2
// Functor handling new data arrival
MarketDataListener mdl;
dds::connection cnt =
reader.on_data_available_signal_connect(
std::bind(&MarketDataListener::handle_data,
&mdl, _1));


OpenSplice DDS

Quality of Service

QoS Model
‣ QoS-Policies are used to control relevant
properties of OpenSplice DDS entities, Type Matching
QoS matching
such as: QoS QoS QoS QoS QoS QoS QoS

‣ Temporal Properties
‣ Priority
Topic
Name

‣ Durability ... DataWriter writes Type reads DataReader
...
...
‣ Availability DomainParticipant writes Type reads DataReader DomainParticipant
DataWriter
‣ ... Name

‣ Some QoS-Policies are matched based on
Topic

QoS QoS QoS
a Request vs. Offered Model thus QoS-
enforcement

‣ Publications and Subscriptions match only if the declared vs. requested QoS are compatible
‣ e.g., it is not possible to match a publisher which delivers data unreliably with a subscriber which requires reliability

QoS Policies
QoS Policy Applicability RxO Modiﬁable Type Matching
QoS matching
DURABILITY T, DR, DW Y N Data Availability QoS QoS QoS QoS QoS QoS QoS

DURABILITY SERVICE T, DW N N
Topic
Name

LIFESPAN T, DW - Y ... DataWriter writes Type reads DataReader
...

T, DR, DW N N ...
HISTORY
DomainParticipant DataWriter writes Type reads DataReader DomainParticipant
PRESENTATION P, S Y N Data Delivery Name
Topic
RELIABILITY T, DR, DW Y N
PARTITION P, S N Y QoS QoS QoS

DESTINATION ORDER T, DR, DW Y N

OWNERSHIP T, DR, DW Y N ‣ Rich set of QoS allow to configure
OWNERSHIP DW - Y
STRENGTH several different aspects of data
DEADLINE T, DR, DW Y Y Data Timeliness availability, delivery and timeliness
LATENCY BUDGET T, DR, DW Y Y

TRANSPORT PRIORITY T, DW - Y
‣ QoS can be used to control and
optimize network as well as
TIME BASED FILTER DR - Y Resources
computing resource
RESOURCE LIMITS T, DR, DW N N

USER_DATA DP, DR, DW N Y Conﬁguration
TOPIC_DATA T N Y
GROUP_DATA P, S N Y


Mapping QoS Which properties does QoS controls?

TimeBasedFilter Deadline

Data
Throughput
Latency

LatencyBudget TransportPriority

Control over Latency/Throughput tradeoff
Control over data latency
Control over data priority



TimeBasedFilter Deadline History

Data Data
Throughput Lifespan Durability
Latency Availability

Ownership
LatencyBudget TransportPriority Ownership
Strength

Control over data queueing
Control over data persistency
Control over data sources hot-swap



TimeBasedFilter Deadline History

Data Data
Throughput Lifespan Durability
Latency Availability

Ownership
LatencyBudget TransportPriority Ownership
Strength

Control over data queueing
Control over data persistency
Control over data sources hot-swap

Reliability
OpenSplice DDS provides programmatic
Destination
QoS-driven support for configuring the most
Presentation Data Delivery
Order important properties of data distribution!
Control over data distribution reliability
Control over data ordering
Control over presentation


OpenSplice DDS

Playing with QoS

History QoS
History Depth = 5

1 1 1 2 1 3 1 4 1 5

DataReader 2 1 2 2 2 3 2 4 2 5

3 1 3 2 3 3 3 4 3 5
1
// Create Reader QoS Topic

dds::DataReaderQos drqos;
drqos.set_keep_last(N);
// Create Reader
‣ The History QoS Controls the number of
dds::DataReader<MarketData> reader(topic, drqos); samples-per-instance that will be stored by
the middleware on behalf of a Reader
2 ‣ Keep Last K. The History QoS can be set so
// Create Reader QoS to always have the latest K samples
dds::DataReaderQos drqos;
drqos.set_keep_all(); ‣ Keep All. The History QoS can be set so
// Create Reader keep all samples produced by the writer and
dds::DataReader<MarketData> reader(topic, drqos);
not yet taken, until resource limits are not
reached

Transport Priority QoS

Make sure that important data gets the right priority Shared Single Copy per Node Shared
Pack Across Topics/Applications
Memory Optimal Unmarshaling Memory
1
// Create Writer QoS
dds::DataWriterQos dwqos;

dwqos.set_priority(MID_PRIO); OpenSplice DDS OpenSplice DDS
// Create Writer Binding
Pre-emptive Network Scheduler
Binding

dds::DataWriter<MarketData> writer(topic, dwqos); Networking Priority Scheduler
Networking
Data Urgency Trafﬁc Pacing
// Write Data
writer.write(data); Network Channels
// Change Priority Priority Bands

dwqos.set_priority(HIGH_PRIO); Trafﬁc Shaping
writer.writer(data)


Ownership QoS
Availability of data producers can be controlled via two QoS Policies
‣ OWNERSHIP
‣ OWNERSHIP STRENGTH
‣ Instances of exclusively owned Topics can be modified (are owned) by the higher strength writer
‣ Writer strength is used to coordinate replicated writers

StockQuote
symbol: "MSFT"
StockQuote
StockQuote
name: "Microsoft Corp."
StockQuote
symbol: "GOOG"
symbol: "GOOG"
exchange: "NASD""GOOG"
symbol:
name: "Google Inc."
quote: 33.73
name: "Google Inc."
name: "Google Inc."
exchange: "NASD"
exchange: "NASD"
exchange: "NASD"
StockQuote
StockQuote
StockQuote
quote: 663.97

W1
quote: 663.97"AAPL"
symbol: "AAPL"
quote: 663.97
symbol: "AAPL"
symbol:
name: "Apple Inc."
name: "Apple Inc."
name: "Apple Inc."
exchange: "NASD"
exchange: "NASD"
exchange: "NASD"

R1
quote: 165.37
quote: 165.37
quote: 165.37

STRENGTH=3

StockQuote
symbol: "AAPL"
StockQuote Inc."
name: "Apple
symbol: "GOOG""NASD"
exchange:
name: quote: 165.37
"Google Inc."
StockQuote "NASD"
exchange:
symbol: "MSFT"
quote: 663.97
exchange: "NASD"
quote: 33.73

W1’ R2
STRENGTH=2 StockQuote
symbol: "AAPL"
StockQuote Inc."
name: "Apple
symbol: "GOOG""NASD"
exchange:
name: quote: 165.37
"Google Inc."
StockQuote "NASD"
exchange:
symbol: "MSFT"
quote: 663.97
exchange: "NASD"
quote: 33.73

W2’’ R3

STRENGTH=1


Ownership QoS
Availability of data producers can be controlled via two QoS Policies
‣ OWNERSHIP
‣ OWNERSHIP STRENGTH
‣ Instances of exclusively owned Topics can be modified (are owned) by the higher strength writer
‣ Writer strength is used to coordinate replicated writers

StockQuote
symbol: "MSFT"
StockQuote
StockQuote
StockQuote
symbol: "GOOG"
symbol: "GOOG"
exchange: "NASD""GOOG"
symbol:
name: "Google Inc."
quote: 33.73
name: "Google Inc."
name: "Google Inc."
exchange: "NASD"
exchange: "NASD"
exchange: "NASD"
quote: 663.97

W1
quote: 663.97
quote: 663.97

StockQuote
symbol: "AAPL"
R1
STRENGTH=3 name: "Apple Inc."
exchange: "NASD"
quote: 165.37

StockQuote
symbol: "GOOG"
name: "Google Inc."
StockQuote "NASD"
exchange:
symbol: "MSFT"
quote: 663.97
exchange: "NASD"
quote: 33.73

W1’ R2
StockQuote
symbol: "AAPL"
name: "Apple Inc."
exchange: "NASD"

STRENGTH=2
quote: 165.37

StockQuote
symbol: "GOOG"
name: "Google Inc."
StockQuote "NASD"
exchange:
symbol: "MSFT"
quote: 663.97
exchange: "NASD"
quote: 33.73

W2’’
StockQuote
symbol: "AAPL"
name: "Apple Inc."
exchange: "NASD"
quote: 165.37
R3

STRENGTH=1


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