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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
  • Header Fields
  • Options Field
  • Returns
  • Errors
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  1. AMPS Command Reference
  2. Commands to AMPS
  3. Subscribing to and Querying Topics

delta_subscribe

The delta_subscribe command is like the subscribe command except that subscriptions placed through delta_subscribe will receive only messages that have changed between the SOW record and the new update.

If delta_subscribe is used on a topic which does not have a SOW store defined, then delta_subscribe behaves like a subscribe command.

Header Fields

The following table contains the header fields available to a delta_subscribe command.

Field

Description

Command

Command to be executed.

Value: delta_publish

Topic

Topic with which to place a subscription.

AckType

Acknowledgment type for the delta_subscribe command.

Value is a comma separated list of one or more of the following: none, received, processed, completed or stats.

CommandId

If specified with an AMPS command requesting an acknowledgment message, all requested acknowledgment messages will contain the CommandId in the acknowledgment response header.

DataOnly

A Boolean (true or false) used to determine the type of data sent to the subscriber.

A value of true will, for example, not include a SOAP envelope.

Filter

String which is used as a content filter expression.

When using XML, the filter must be wrapped in a CDATA.

Options

A comma separated list of flags available to the subscribe command.

SendEmpty

Boolean (true or false) value used to determine whether empty messages which are published will be forwarded to matching subscriptions.

Default: true

SendSubscriptionIds

Boolean (true or false) subscription identifiers will not be sent for all matched messages if set to false.

SubscriptionId

The subscription ID for this command. When provided with a new subscription, this is the identifier that AMPS will use for the subscription.

When provided with the replace option, this field specifies the subscription to replace.

When provided with a pause or resume option, this field specifies the subscriptions to pause or resume.

For a new subscription, the AMPS clients will generate a subscription ID if one is not provided.

Bookmark

A bookmark specifying the point in the transaction log at which to start the subscription.

If the topic provided is not recorded in a transaction log, AMPS enters the subscription without replaying messages.

You can provide a single bookmark, or a comma-delimited list of bookmarks.

When a list is provided, AMPS starts the subscription at the earliest bookmark in the list.

Options Field

The following table contains a list of the Options available and their definitions when used in the AMPS sow_and_delta_subscribe command.

Option

Description

none

This is the default Options type.

bookmark

Specifies that the subscription should return bookmarks, if available, on each publish message. Bookmarks are only available if the topic that is subscribed to is recorded in the transaction log.

Notice that this option does not set the starting point for a bookmark subscription: use the Bookmark header for that purpose.

This option is not required to receive bookmarks for a bookmark subscription. Those subscriptions always include bookmarks on each publish message.

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).

Default: none

conflation_key=[key]

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.

live

Tells AMPS to send messages to subscribing clients before they have been persisted to the transaction log.

This option has no effect on subscriptions that are not replays from the transaction log (that is, this option only applies to bookmark subscriptions).

max_backlog=n

When subscribing to a queue, the number of unacknowledged messages the client is willing to accept at a time.

AMPS will not exceed this number, but may choose a smaller number depending on the queue configuration.

no_empties

Tells AMPS not to send empty publish messages to matching subscriptions.

This can be useful for suppressing messages where no fields have changed.

no_sowkey

Tells AMPS not to send the AMPS-generated SowKey for messages.

non_regex_topic

Specifies that the topic name should be a literal match, even if the topic name contains regular expression characters.

oof

Send an OOF message for records which have fallen out of focus from the original subscription.

When focus tracking is enabled, AMPS will also deliver the full message to a subscription when a previously out-of-focus message comes into focus.

pause

Pause a bookmark subscription.

This option is only valid for bookmark subscriptions that do not use the live option. When this option is present, AMPS pauses the subscription or subscriptions provided in the SubId of the command.

rate=n

Set the maximum message delivery rate for a bookmark subscription.

This option is only valid for bookmark subscriptions that do not use the live option.

The rate can be specified as either the number of messages per second (for example, 1000), the number of bytes per second (for example, 100KB), or a multiple of the original replay rate (for example, 1.5X).

replace

Replace the subscription associated with CmdId with another subscription. When provided as part of sow_and_subscribe, AMPS runs a SOW query for the new subscription.

resume

Resume a bookmark subscription. This option is only valid for bookmark subscriptions that do not use the live option.

When this option is present, AMPS resumes the subscription or subscriptions provided in the SubId of the command.

send_keys

AMPS will send the SOW keys fields back with messages from the SOW.

Notice that without this option, messages will never contain these fields (since, by definition, they do not change from update to update).

timestamp

AMPS will include a header with the time at which this instance of AMPS processed the incoming publish command for this message.

Returns

A delta_subscribe command returns the following command types:

Command

Description

publish

A message published to AMPS.

oof

Returned when the oof option is requested on the command, the subscription is to a topic in the SOW, and the subscription is not a bookmark subscribe.

ack

Acknowledgments requested, as described in the following section.

For a delta_subscribe message, AMPS will send acknowledgment messages for the following AckType fields: received, processed, persisted and stats along with a populated Status header field describing the acknowledgment.

The following table contains the AckType messages which can be returned by a delta_subscribe.

Acknowledgment

Description

none

No ack is returned.

This is the default behavior.

completed

When a bookmark is present on the subscribe request and this acknowledgment is requested, AMPS sends a completed acknowledgment message to indicate that bookmark replay is complete. Further messages on this subscription are from new publishes.

persisted

When a bookmark is present and this acknowledgment is requested, AMPS periodically sends a persisted acknowledgment message to indicate the most recent bookmark in the server's transaction log.

processed

AMPS has compiled the filters for the delta_subscribe message(s).

received

The delta_subscribe message has been received.

stats

Returns an acknowledgment message with Matches, TopicMatches and RecordsReturned.

Errors

Any errors that occur during this command will be returned in the status of a processed acknowledgment and logged to the log file. Regardless of success or failure, the processed acknowledgment will be returned only if requested by including processed in the AckType field of the delta_subscribe message header.

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Last updated 6 months ago

The table below describes the Options available for use in the delta_subscribe command.

Options Field