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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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  1. AMPS Configuration Guide
  2. State of the World (SOW)

SOW/View

This section contains a listing of the parameters for a View section in the SOW section of an AMPS configuration file. For backward compatibility, AMPS accepts ViewDefinition as a synonym for View.

Element

Definition

MessageType (required)

The message type of the view. This does not need to be the same type as any of the topics in the aggregation, but does need to be a message type that supports views.

The message type must be one of the message types configured for the instance. AMPS includes fix, xml, nvfix, json, bson and bflat message types with full support for views. You can also use any custom message type defined for the configuration file, provided that the message type supports views.

Notice that the binary message type does not specify a fixed format for the message contents, so that message type cannot be used in a view.

Name (required)

Defines the topic name for this view.

If no Name is provided, AMPS accepts Topic as a synonym for Name to provide compatibility with versions of AMPS previous to 5.0.

UnderlyingTopic (required)

Defines the SOW topic or topics on which this view is based.

This element can contain a single topic name, or any number of Join elements.

Projection/Field (required)

Defines what the view will contain.

This element can be specified multiple times to compose a complex view. Complex expressions that use aggregation functions and conditional branching can also be used.

Grouping/Field (required)

Defines how the records in the underlying topic will be grouped.

This is analogous to a SQL GROUP BY clause.

KeyDomain

The seed value for SowKeys used within this topic.

The default is the topic name, but it can be changed to a string value to unify SowKey values between different topics.

Join

Within an UnderlyingTopic, each Join specifies two topics to join together to create the view, as well as the relationship between those topics.

An UnderlyingTopic can have any number of Join specifications. For more information on Join specifications, see the AMPS User Guide.

Conflation

Defines whether AMPS will attempt to conflate updates to the view.

This item accepts two values:

  • none - No conflation. AMPS fully processes every update to the view, in publication order.

  • inline - Conflation is active. AMPS conflates multiple updates to the same underlying record where possible. See the AMPS User Guide for details.

Default: none

Filter

Defines a filter for the view. When provided, only messages from the underlying topic that match this filter will be included in the view.

This option is only valid when the view uses a single UnderlyingTopic. When the view contains a Join specification, this option may not be used.

Default: No filter, which includes all messages from the UnderlyingTopic.

HashIndex

AMPS provides the ability to do fast query lookup for records in a view based on specific fields.

When one or more HashIndex elements are provided, AMPS creates a hash index for the fields specified in the element. These indexes are created on startup, and are kept up to date as records are added, removed, and updated.

The HashIndex element contains a Key element for each field in the hash index.

AMPS uses a hash index when a query uses an exact string match for all of the fields in the index. AMPS does not use hash indexes for range queries or regular expressions, or for numeric comparisons.

AMPS automatically creates a hash index for the fields specified in the Grouping for the view.

JoinNullEquivalency

Specifies whether the Join expressions in this view should consider NULL values to be equivalent.

When this is enabled, missing values, empty strings, and NULL values will be considered to match in a Join expression. When this is disabled, these values will not match.

Default: disabled

FileName

File location to store view data. Unused in this version of AMPS.

<SOW>
    <!-- Single topic aggregation -->
    <Topic>
        <Topic>/ett/order</Topic>
        <MessageType>fix</MessageType>
        <Key>/orderId</Key>
    </Topic>
    <View>
        <MessageType>nvfix</MessageType>
        <Topic>TOTAL_VALUE</Topic>
        <UnderlyingTopic>/ett/order</UnderlyingTopic>
        <Projection>
            <Field>/109</Field>
            <Field>SUM(/14 * /6) AS /71406</Field>
        </Projection>
        <Grouping>
            <Field>/109</Field>
        </Grouping>
    </View>

    <!-- Single topic aggregation with filter -->
    <Topic>
        <Name>orders</Name>
        <MessageType>json</MessageType>
        <Key>/orderId</Key>
        <FileName>./sow/%n.sow</FileName>
    </Topic>
    <View>
        <Name>CompleteByRegion</Name>
        <UnderlyingTopic>orders</UnderlyingTopic>
        <MessageType>json</MessageType>
        <Projection>
            <Field>COUNT(/orderId) AS /completedOrders</Field>
            <Field>/region AS /region</Field>
        </Projection>
        <Grouping>
            <Field>/region</Field>
        </Grouping>
        <Filter>/status = 'complete'</Filter>
    </View>

  <!-- Single topic aggregation with a hash index
       for faster query. -->
  <Topic>
      <Name>source-for-hash-sample</Name>
      <MessageType>json</MessageType>
      <Key>/id</Key>
      <FileName>./sow/%n.sow</FileName>
  </Topic>
  <View>
      <Name>hash-sample-view</Name>
      <MessageType>json</MessageType>
      <UnderlyingTopic>source-for-hash-sample</UnderlyingTopic>
      <Projection>
         <Field>SUM(/qty) as /quantity</Field>
         <Field>/customerName</Field>
         <Field>/orderType</Field>
       </Projection>
       <Grouping>
         <Field>/customerName</Field>
         <Field>/orderType</Field>
       </Grouping>
       <!-- provide fast query for exact matches on
            *either* name or orderType -->
       <HashIndex>
          <Key>/name</Key>
       </HashIndex>
       <HashIndex>
          <Key>/orderType</Key>
       </HashIndex>
   </View>

    <!-- Project from one message type to another -->
    <Topic>
        <Name>example</Name>
        <MessageType>json</MessageType>
        <Key>/id</Key>
        <FileName>./sow/%n.sow</FileName>
    </Topic>
    <View>
        <!-- notice that nvfix topic named 'example' is not the same topic as the json
            topic named 'example' -->
        <Name>example</Name>
        <MessageType>nvfix</MessageType>
        <UnderlyingTopic>[json].[example]</UnderlyingTopic>
        <Projection>
            <Field>[json].[example]./id AS /id</Field>
        </Projection>
        <Grouping>
            <Field>[json].[example]./id</Field>
        </Grouping>
    </View>

   <!-- JOIN topics -->
   <Topic>
        <Name>ORDERS</Name>
        <MessageType>nvfix</MessageType>
        <Key>/OrderID</Key>
        <FileName>./sow/%n.sow</FileName>
    </Topic>
    <Topic>
        <Name>COMPANIES</Name>
        <MessageType>nvfix</MessageType>
        <Key>/CompanyId</Key>
        <FileName>./sow/%n.sow</FileName>
    </Topic>
    <View>
        <Name>TOTAL_COMPANY_VOLUME</Name>
        <UnderlyingTopic>
            <Join>[ORDERS]./Tick = [COMPANIES]./Tick</Join>
        </UnderlyingTopic>
        <MessageType>nvfix</MessageType>
        <Projection>
            <Field>[COMPANIES]./CompanyId</Field>
            <Field>[COMPANIES]./Tick</Field>
            <Field>[COMPANIES]./Name</Field>
            <Field>SUM([ORDERS]./Shares) AS /TotalVolume</Field>
        </Projection>
        <Grouping>
            <Field>[ORDERS]./Tick</Field>
        </Grouping>
    </View>
</SOW>
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Last updated 1 year ago

Other message types provided with AMPS may have limitations in their support for views. See the section in the AMPS User Guide for a discussion of the limitations.

Message Types