SOW Queries¶

AMPS provides a powerful State of the World (SOW) feature — a server-side queryable cache that maintains the latest state of each record. The AMPS binder supports three subscription modes that leverage SOW.

Subscription Modes¶

The default mode. The consumer receives only live updates as they are published. No historical data is delivered.

spring.cloud.stream.amps.bindings:
  orders-in-0:
    consumer:
      # snapshot: false (default)
      # sow: false (default)

SOW (Snapshot Only)¶

The consumer receives a one-time snapshot of the current state from the SOW cache and then stops. No live updates are delivered after the snapshot completes.

This is useful for loading initial state on startup or performing periodic queries.

spring.cloud.stream.amps.bindings:
  orders-in-0:
    consumer:
      snapshot: true

AMPS Command

This translates to the AMPS SOW command.

The consumer first receives the full SOW snapshot, then seamlessly transitions to receiving live updates. This is the most common mode for applications that need both historical state and real-time data.

spring.cloud.stream.amps.bindings:
  orders-in-0:
    consumer:
      sow: true

AMPS Command

This translates to the AMPS SOWAndSubscribe command.

Decision Matrix¶

`snapshot`	`sow`	Command	Historical Data	Live Updates
`false`	`false`	`Subscribe`	No	Yes
`false`	`true`	`SOWAndSubscribe`	Yes	Yes
`true`	any	`SOW`	Yes	No

Content Filtering with SOW¶

Combine SOW queries with content filters to receive only matching records:

spring.cloud.stream.amps.bindings:
  active-orders-in-0:
    consumer:
      sow: true
      filter: "/status = 'ACTIVE' AND /region = 'US'"

Out-of-Focus (OOF) Messages¶

When using SOW-and-Subscribe with a filter, enable OOF to receive notifications when a record no longer matches the filter or is deleted from the SOW cache:

spring.cloud.stream.amps.bindings:
  active-orders-in-0:
    consumer:
      sow: true
      filter: "/status = 'ACTIVE'"
      oof: true

An OOF message is delivered when:

A record's field is updated such that it no longer matches the filter.
A record is deleted from the SOW.

Batch Size¶

Control how many SOW records the server sends per batch:

spring.cloud.stream.amps.bindings:
  orders-in-0:
    consumer:
      sow: true
      batchSize: 500

Timeout¶

Set a timeout for the SOW query. If the server doesn't respond within this period, the subscription fails:

spring.cloud.stream.amps.bindings:
  orders-in-0:
    consumer:
      snapshot: true
      timeout: 60s

Example: Full SOW Configuration¶

spring:
  cloud:
    stream:
      amps:
        binder:
          brokers:
            - tcp://amps-server:50000/json
        bindings:
          orders-in-0:
            consumer:
              sow: true
              filter: "/quantity > 100"
              oof: true
              bookmarkType: MOST_RECENT
              batchSize: 200
              timeout: 30s
              ackBatchSize: 50
              ackTimeout: 5s
      bindings:
        orders-in-0:
          destination: orders