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AMPS Server Documentation 5.3.4
AMPS Server Documentation 5.3.4
  • Welcome to AMPS 5.3.4
  • Introduction to AMPS
    • Overview of AMPS
    • Getting Started With AMPS
      • Installing AMPS
      • Starting AMPS
      • JSON Messages - A Quick Primer
      • spark: the AMPS command-line client
      • Evaluating AMPS on Windows or MacOS
      • Galvanometer and RESTful Statistics
    • AMPS Basics: Subscribe and Publish to Topics
    • State of the World (SOW): The Message Database
      • When Should I Store a Topic in the SOW?
      • How Does the SOW Work?
      • Configuration
      • Queries
      • Atomic Query and Subscribe
      • Advanced Messaging and the SOW
    • Record and Replay Messages with the AMPS Transaction Log
    • Message Queues
    • Scenario and Feature Reference
      • Recovery Strategies
    • Getting Support
    • Advanced Topics
    • Next Steps
  • AMPS Evaluation Guide
    • Introduction
    • Evaluation and Development with AMPS
    • Tips on Measuring Performance
    • Next Steps
  • AMPS User Guide
    • Introduction
      • Product Overview
      • Requirements
      • Organization of this Guide
        • Documentation Conventions
      • Technical Support
    • Installing and Starting AMPS
      • Installing AMPS
      • Starting AMPS
      • Production Configuration
    • Subscribe and Publish
      • Topics
      • Filtering Subscriptions by Content
      • Conflated Subscriptions
      • Replacing Subscriptions
      • Messages in AMPS
      • Message Ordering
      • Retrieving Part of a Message
    • AMPS Expressions
      • Syntax
      • Identifiers
      • AMPS Data Types
      • Grouping and Order of Evaluation
      • Logical Operators
      • Arithmetic Operators
      • Comparison Operators
      • LIKE Operator
      • Conditional Operators
      • Working with Arrays
      • Regular Expressions
      • Performance Considerations
    • AMPS Functions
      • AMPS Function Overview
      • String Comparison Functions
      • Concatenating Strings
      • Managing String Case
      • Replacing Text in Strings
      • String Manipulation Functions
      • Date and Time Functions
      • Array Reduce Functions
      • Geospatial Functions
      • Numeric Functions
      • CRC Functions
      • Message Functions
      • Client Functions
      • Coalesce Function
      • AMPS Information Functions
      • Typed Value Creation
      • Constructing Fields
      • Aggregate Functions
    • State of the World (SOW) Topics
      • How Does the SOW Work?
      • Using the State of the World
      • Understanding SOW Keys
      • Indexing SOW Topics
      • Programmatically Deleting Records from the Topic State
      • SOW Maintenance
        • Creating a Maintenance Schedule for a Topic
        • Setting Per-Message Lifetime
      • Storing Multiple Logical Topics in One Physical Topic
    • Querying the State of the World (SOW)
      • Overview of SOW Queries
      • Query and Subscribe
      • Historical SOW Topic Queries
      • Managing Result Sets
      • Batching Query Results
    • Out-of-Focus Messages (OOF)
    • State of the World Message Enrichment
    • Incremental Message Updates
      • Using Delta Publish
      • Understanding Delta Publish
      • Delta Publish Support
    • Receiving Only Updated Fields
      • Using Delta Subscribe
      • Identifying Changed Records
      • Conflated Subscriptions and Delta Subscribe
      • Select List and Delta Subscribe
      • Options for Delta Subscribe
    • Conflated Topics
    • Aggregation and Analytics
      • Understanding Views
      • Defining Views and Aggregations
      • Constructing Field Contents
      • Best Practices for Views
      • View Examples
      • Aggregated Subscriptions
    • Record and Replay Messages
      • Using the Transaction Log and Bookmark Subscriptions
      • Understanding Message Persistence
      • Configuring a Transaction Log
      • Replaying Messages with Bookmark Subscription
      • Managing Journal Files
      • Using amps-grep to Search the Journal
    • Message Queues
      • Getting Started with AMPS Queues
      • Understanding AMPS Queuing
      • Advanced Messaging and Queues
      • Replacing Queue Subscriptions
      • Handling Unprocessed Messages
      • Advanced Queue Configuration
      • Queue Subscriptions Compared to Bookmark Replays
    • Message Types
      • Default Message Types
      • BFlat Messages
      • MessagePack Messages
      • Composite Messages
      • Protobuf Message Types
      • Struct Message Types
    • Command Acknowledgment
      • Requesting Acknowledgments
      • Receiving Acknowledgments
      • Bookmark Subscriptions and Completed Acknowledgments
      • Bookmark Subscriptions and Persisted Acknowledgments
      • Acknowledgment Conflation and Publish Acknowledgements
    • Transports
      • Client Connections
      • Replication Connections
      • Transport Filters
    • Running AMPS as a Linux Service
      • Installing the Service
      • Configuring the Service
      • Managing the Service
      • Uninstalling the Service
    • Logging
      • Configuring Logging
      • Log Message Format
      • Message Levels
      • Message Categories
      • Logging to a File
      • Logging to a Compressed File
      • Logging to Syslog
      • Logging to the Console
      • Looking up Errors with ampserr
    • Event Topics
      • Client Status Events
      • SOW Statistics Events
      • Persisting Event Topics
    • Utilities
      • Command-Line Basic Client
      • Dump clients.ack File
      • Dump journal File
      • Dump queues.ack File
      • Dump SOW File
      • Dump Journal Topic Index File
      • Find Bookmark or Transaction ID in Transaction Log
      • Find Information in Error Log or Transaction Log
      • Identify Type of AMPS File
      • List/Explain Error Codes
      • Query Statistics Database
      • Statistics Database Report
      • Storage Performance Testing
      • Submit Minidump to 60East
      • Obsolete Utility: Upgrade File Formats
    • Monitoring AMPS
      • Statistics Collection
        • Time Range Selection
        • Output Formatting
      • Galvanometer
      • Configuring Monitoring
    • Automating AMPS with Actions
    • Replicating Messages Between Instances
      • Replication Basics
      • Configuring Replication
      • Replication Configuration Validation
      • Replication Resynchronization
      • Replication Compression
      • Destination Server Failover
      • Two-Way Replication
      • PassThrough Replication
      • Guarantees on Ordering
      • Replication Security
      • Understanding Replication Message Routing
      • Replicated Queues
      • Replication Best Practices
    • Highly Available AMPS Installations
      • Overview of High Availability
        • Example: Pair of Instances for Failover
        • Example: Regional Distribution
        • Example: Regional Distribution with HA
        • Example: Hub and Spoke / Expandable Mesh
      • Details of High Availability
      • Slow Client Management and Capacity Limits
      • Message Ordering Considerations
    • Operation and Deployment
      • Capacity Planning
      • Linux OS Settings
      • Upgrading AMPS
      • Using AMPS with a Proxy
      • Operations Best Practices
    • Securing AMPS
      • Authentication
      • Entitlement
      • Providing an Identity for Outbound Connections
      • Protecting Data in Transit Using TLS/SSL
    • Troubleshooting AMPS
      • Planning for Troubleshooting
      • Diagnostic Utilities
      • Finding Information in the Log
      • Reading Replication Log Messages
      • Troubleshooting Disconnected Clients
      • Troubleshooting Regular Expression Subscriptions
    • AMPS Distribution Layout
    • Optionally-Loaded Modules
      • Optional Functions
        • Legacy Messaging Functions
        • Special-Purpose Functions
      • Optional SOW Key Generator
        • Chaining Key Generator
      • Optional Authentication/Entitlements Modules
        • RESTful Authentication and Entitlements
        • Multimethod Authentication Module
        • Simple Access Entitlements Module
      • Optional Authenticator Modules
        • Multimethod Authenticator
        • Command Execution Authenticator
    • AMPS Statistics
    • File Format Versions
  • AMPS Configuration Guide
    • AMPS Configuration Basics
      • Getting Started With AMPS Configuration
      • Units, Intervals, and Environment Variables
      • Working With Configuration Files
      • Including External Files
    • Instance Level Configuration
    • Admin Server and Statistics
    • Modules
    • Message Types
    • Transports
    • Logging
    • State of the World (SOW)
      • SOW/Topic
      • SOW/*Queue
      • SOW/ConflatedTopic
      • SOW/View
    • Replication
      • Replication Validation
    • Transaction Log
    • Authentication
    • Entitlement
    • Actions
      • Configuration for Actions
      • Choosing When an Action Runs
        • On a Schedule
        • On AMPS Startup or Shutdown
        • On a Linux Signal
        • On a REST Request
        • On Minidump Creation
        • On Client Connect or Disconnect
        • On Client Logon
        • On Client Offline Message Buffering
        • On Subscribe or Unsubscribe
        • On Incoming Replication Connections
        • On Outgoing Replication Connections
        • On Message Published to AMPS
        • On Message Delivered to Subscriber
        • On Message Affinity
        • On SOW Message Expiration
        • On SOW Message Delete
        • On OOF Message
        • On Message Condition Timeout
        • On Message State Change
        • On a Custom Event
      • Choosing What an Action Does
        • Rotate Error/Event Log
        • Compress Files
        • Truncate Statistics
        • Manage Transaction Log Journal Files
        • Remove Files
        • Delete SOW Messages
        • Compact SOW Topic
        • Query SOW Topic
        • Manage Security
        • Enable or Disable Transports
        • Publish Message
        • Manage Replication Acknowledgment
        • Extract Values from a Message
        • Translate Data Within an Action
        • Increment Counter
        • Raise a Custom Event
        • Execute System Command
        • Manage Queue Transfers
        • Create Minidump
        • Shut Down AMPS
        • Debug Action Configuration
      • Conditionally Stopping an Action
        • Based on File System Capacity
        • Based on an Expression
      • Examples of Action Configuration
        • Archive Journals Once a Week
        • Archive Journals On RESTful Command
        • Record Expired Queue Messages to a Dead Letter Topic
        • Copy Messages that Exceed a Timeout to a Different Topic
        • Deactivate and Reactivate Security on Signals
        • Reset Entitlements for a Disconnected Client
        • Extract Values from a Published Message
        • Shut Down AMPS When a Filesystem Is Full
        • Increment a Counter and Echo a Message
    • Protocols
  • AMPS Monitoring Guide
    • Statistics Types
    • Table Reference
    • Administrative Actions
    • Host Statistics
      • cpu
      • disks
      • memory
      • name
      • network
    • AMPS Instance Statistics
      • api
      • clients
      • config.xml
      • config_path
      • conflated_topics
      • cpu
      • cwd
      • description
      • environment
      • lifetimes
      • logging
      • memory
      • message_types
      • name
      • name_hash
      • pid
      • processors
      • queues
      • queries
      • replication
      • sow
      • statistics
      • subscriptions
      • timestamp
      • transaction_log
      • transports
      • tuning
      • uptime
      • user_id
      • version
      • views
  • AMPS Command Reference
    • Commands to AMPS
      • logon
      • Publishing
        • publish
        • delta_publish
      • Subscribing to and Querying Topics
        • subscribe
        • sow
        • sow_and_subscribe
        • unsubscribe
        • delta_subscribe
        • sow_and_delta_subscribe
      • Removing Messages (SOW/Topic or Message Queue)
      • heartbeat
      • flush
    • Responses from AMPS
      • sow: Content from Server
      • publish: Content from Server
      • oof: Content from Server
      • ack: Status from Server
      • group_begin / group_end : Result Set Delimiters
    • Protocol Reference
      • AMPS Protocol
      • Legacy Protocols Reference
    • Command Cookbook
      • Cookbook: Delta Publish
      • Cookbook: Delta Subscribe
      • Cookbook: Publish
      • Cookbook: SOW
      • Cookbook: SOW and Delta Subscribe
      • Cookbook: SOW and Subscribe
      • Cookbook: SOW Delete
      • Cookbook: Subscribe
  • Deployment Checklist
    • Ensure Sufficient Capacity
    • Apply System and AMPS Configuration
    • Create Maintenance Plan
    • Create Monitoring Strategy
    • Create Patch and Upgrade Plan
    • Create and Test Support Process
    • Conclusion
  • AMPS Clients
    • Performance Tips and Best Practices
    • C++
    • C#/.NET
    • Java
    • JavaScript
    • Python
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On this page
  • When to Use Conflated Subscriptions
  • Requesting Conflation on a Subscription
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  1. AMPS User Guide
  2. Subscribe and Publish

Conflated Subscriptions

PreviousFiltering Subscriptions by ContentNextReplacing Subscriptions

Last updated 1 year ago

AMPS provides the ability for the server to conflate messages to a subscription. When a subscription requests conflation, the server will retain messages for that subscription for a certain period of time, the conflation interval, and provide the latest update to that message once a message has been retained for that interval. In effect, AMPS guarantees that a subscription will receive no more than one update for a given message per conflation interval.

Conflated subscriptions provide a way to reduce the bandwidth and processing for a subscriber in cases where a subscriber needs periodic updates with the current state of a message, rather than the complete message stream. AMPS provides per-subscription conflation for cases where only a small number of subscribers require conflation, or if conflation is required only in unusual cases. If multiple subscribers will have the same conflation needs, consider using .

For example, imagine an application that monitors selected stocks and displays the current prices on a large screen, which refreshes every few seconds. This application may use the same topics as a trading desk, but has very different needs for data freshness and completeness. Since updates to each symbol will only be displayed every few seconds, the application only needs point-in-time updates of the prices, rather than the full stream of price changes. To meet this need, the application could specify that the subscription conflates price updates by tickerId with a conflation interval of two seconds. For each distinct value of the tickerId field, AMPS will retain messages for two seconds. If another message with the same tickerId is processed for the subscription during the conflation interval, that message completely replaces the previous message. At the end of the two second conflation interval, the message is delivered to the application. This lets the application receive an up-to-date price at most every two seconds, without having to process a large number of updates that will never be displayed. This approach also ensures that the price is never more than two seconds out of date, which means that each time the screen is refreshed, the price is current.

As mentioned in the example above, if the subscription uses tickerId for conflation and the following sequence of messages arrive during a conflation interval:

{ "tickerId" : "IBM", "price" : 150.34 }
{ "tickerId" : "IBM", "price" : 149.76 }
{ "tickerId" : "IBM", "price" : 149.32 }
{ "tickerId" : "IBM", "price" : 151.10 }

AMPS delivers only the last message for that tickerId:

{ "tickerId" : "IBM", "price" : 151.10 }

Notice that when a subscription is conflated, AMPS does not guarantee that messages are delivered precisely in the order in which they arrived in AMPS, since the latest update is delivered based on the conflation interval.

When the timestamp option is used with conflated subscriptions, AMPS provides the timestamp for the first message conflated.

When to Use Conflated Subscriptions

Conflated subscriptions reduce the bandwidth for a subscription, and may reduce the processing resources required for a subscription. However, rather than immediately delivering messages, AMPS retains messages in memory for the conflation interval. This can increase the memory required for the subscription.

AMPS contains other features for conflating messages and reducing bandwidth. Conflated subscriptions are most appropriate when:

  • Network bandwidth is at a premium, and you would like AMPS to spend slightly more processing time and potentially more memory to reduce the bandwidth needs of the application.

  • Each subscription has different conflation needs. For example, if each subscription has a dramatically different conflation interval, or needs to conflate by different fields. If most subscribers will use a similar conflation interval and use the same fields for conflation, using a Conflated Topic can provide equivalent results with lower overhead.

  • The conflation needs are relatively predictable and consistent for the subscription. If you need the application to conflate messages only when processing is slow or there are bursts of message traffic, client-side conflation provides that ability and may be a better choice than a conflated subscription. See the developer guide for your programming language of choice for details.

The considerations above are general guidance to help you consider options and choose a conflation strategy.

Requesting Conflation on a Subscription

To request conflation on a subscription, set the following options on the subscription:

Option
Description

conflation=n

Specifies whether to conflate this subscription. The value provided can be a time interval, auto or none.

When present and set to a value other than none, enables conflation for the subscription.

Can also be set to auto, which requests that AMPS attempt to determine an appropriate conflation interval based on client consumption.

Recognizes the same time specifiers used in the AMPS configuration file (for example, 100ms or 1s or 1m).

Defaults to none.

conflation_key=[keys]

When conflation is enabled, specifies the fields to use to determine message uniqueness. The format of this option is a comma-delimited list of XPath identifiers within brackets.

For example, to conflate based on the value of the /tickerId and /customerId within a message. the value of this option would be:

[/tickerId,/customerId]

Defaults to the SOW key fields for SOW topics.

No default for non-SOW topics. This option is required for non-SOW topics.

This option is not valid with the oof option unless the keys provided are identical to the keys for the topic.

This option can only be used when conflation is also specified.

For example, to request a 10 second conflation interval with messages conflated on the [/orderId] field, you would use the following options string:

conflation=10s,conflation_key=[/orderId]

You can also combine approaches as necessary. For example, if most of your subscriptions require a 3 second conflation interval by tickerId, while a few subscriptions require a 15 second interval, you could create a with a 3 second interval. Those subscriptions that require a 15 second interval could subscribe with that interval. This provides both sets of subscriptions with the intervals that they need.

Conflated Topics
Conflated Topic