Processing Records10% of the exam
Object Store watermarks between flow executions
Persist a watermark between Scheduler runs with the Object Store connector: Retrieve with a default value and a target, Store with `failIfPresent` and `failOnNullValue`, persistent versus transient stores, and what changes with Object Store v2 on CloudHub.
Apply correct processors/syntax to persist data between flow executions.
~7 min read · 5 practice questions ·
What the exam expects
- Choose the Object Store connector, not a variable, attribute or payload, to keep a value from one flow execution to the next.
- Configure Retrieve with
<os:default-value>andtarget, and predict the payload, the variable and the store contents afterwards. - Configure Store with
failIfPresentandfailOnNullValue, and name the error each default raises. - Choose between the default store, a custom persistent store and a transient store.
- State what changes when a CloudHub app switches to Object Store v2.
Key terms:
- Object store: a key-value facility Mule uses to persist data for later retrieval.
- Watermark: the stored point where the next periodic synchronization should resume.
- Default object store: the persistent store every app has without configuration.
- Object Store v2: the CloudHub object store implementation selected in Runtime Manager.
Key facts
Default object store
- Detail
- Persistent, available with no configuration
Transactions
- Detail
- Object stores do not support transactional access
Retrieve, missing key, no default
- Detail
OS:KEY_NOT_FOUND
Retrieve default value
- Detail
- Returned but not stored
Retrieve without
target- Detail
- Value becomes the payload
failIfPresent- Detail
- Default
falseoverwrites;truegivesOS:KEY_ALREADY_EXISTS
failOnNullValue- Detail
- Default
truegivesOS:NULL_VALUE;falsedoes nothing
Transient store
- Detail
- Data does not survive a runtime crash
v1 to v2 switch
- Detail
- Data, including watermarks, does not carry over
Object Store v2 entries
- Detail
- Unlimited; values up to 10 MB Base64-encoded
On-premises access to v2
- Detail
- Only through the Object Store REST API
- What does Retrieve do when the key is missing and no default value is set?
- Why does the documented watermark Retrieve use
target? - When does a watermark Store fail on the second run?
- Why must watermarks be backed up before switching a CloudHub app to Object Store v2?
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