List Commands

List commands operate on Redis lists — ordered collections of strings. Lists are doubly-linked, so adding elements to the head or tail is very fast.

This page covers: BLMOVE, BLPOP, BRPOP, LMOVE, LPOP, LPUSH, LSET, RPOP, RPUSH

LPUSH

Prepend one or more values to a list.

📘 Redis Reference: LPUSH

XML Example

xml

<lettuce-redis:lpush doc:name="Push to queue"
    config-ref="Redis_Config"
    key="queue:tasks"
    members="#[['task-1', 'task-2', 'task-3']]"/>

Parameters

Parameter	Type	Required	Default	Description
`key`	String	Yes	—	The list key
`members`	List<String>	Yes	—	Values to prepend. At least one required. Payload by default via `@Content`.

Output

Type: Long

The length of the list after the operation.

Errors

Error Type	Condition
`REDIS:ARGUMENT`	No members provided
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	Key exists but is not a list

RPUSH

Append one or more values to a list.

📘 Redis Reference: RPUSH

XML Example

xml

<lettuce-redis:rpush doc:name="Append to log"
    config-ref="Redis_Config"
    key="log:events"
    members="#[['event-1', 'event-2']]"/>

Parameters

Parameter	Type	Required	Default	Description
`key`	String	Yes	—	The list key
`members`	List<String>	Yes	—	Values to append. At least one required. Payload by default via `@Content`.

Output

Type: Long

The length of the list after the operation.

Errors

Error Type	Condition
`REDIS:ARGUMENT`	No members provided
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	Key exists but is not a list

LPOP

Remove and return the first element(s) from a list.

📘 Redis Reference: LPOP

XML Example

xml

<!-- Pop a single element -->
<lettuce-redis:lpop doc:name="Pop one"
    config-ref="Redis_Config"
    key="queue:tasks"/>
<!-- payload is a List<String> with one element -->

<!-- Pop multiple elements -->
<lettuce-redis:lpop doc:name="Pop three"
    config-ref="Redis_Config"
    key="queue:tasks"
    count="3"/>
<!-- payload is a List<String> with up to three elements -->

Parameters

Parameter	Type	Required	Default	Description
`key`	String	Yes	—	The list key
`count`	Integer	No	—	Number of elements to pop. When omitted, pops one element.

Output

Type: List<String>

The operation always returns a List<String> regardless of whether count is provided:

When count is not specified: list contains a single element (the popped element)
When count is specified: list contains up to count popped elements

Metadata Mismatch

Anypoint Studio's design-time metadata indicates this operation returns a String when count is not provided. At runtime, the operation always returns a List<String>. When writing DataWeave expressions, treat the output as a list. This mismatch is tracked in issue #4.

Errors

Error Type	Condition
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	Key exists but is not a list

RPOP

Remove and return the last element(s) from a list.

📘 Redis Reference: RPOP

XML Example

xml

<!-- Pop a single element -->
<lettuce-redis:rpop doc:name="Pop last"
    config-ref="Redis_Config"
    key="stack:items"/>
<!-- payload is a List<String> with one element -->

<!-- Pop multiple elements -->
<lettuce-redis:rpop doc:name="Pop last three"
    config-ref="Redis_Config"
    key="stack:items"
    count="3"/>
<!-- payload is a List<String> with up to three elements -->

Parameters

Parameter	Type	Required	Default	Description
`key`	String	Yes	—	The list key
`count`	Integer	No	—	Number of elements to pop

Output

Type: List<String>

The operation always returns a List<String> regardless of whether count is provided:

When count is not specified: list contains a single element (the popped element)
When count is specified: list contains up to count popped elements

Metadata Mismatch

Errors

Error Type	Condition
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	Key exists but is not a list

BLPOP

Remove and return the first element from one of multiple lists, blocking until an element is available or timeout occurs.

📘 Redis Reference: BLPOP

XML Example

xml

<!-- Block for up to 5 seconds waiting for a task -->
<lettuce-redis:blpop doc:name="Wait for task"
    config-ref="Redis_Config"
    keys="#[['queue:high-priority', 'queue:normal', 'queue:low']]"
    timeoutSeconds="5"/>

<!-- payload is a Map<String, String> with one entry: the key and the popped value -->
<logger level="INFO"
    message="Popped from #[payload.keys()[0]]: #[payload[payload.keys()[0]]]"/>

Parameters

Parameter	Type	Required	Default	Description
`keys`	List<String>	Yes	—	One or more list keys to wait on. At least one required. The first list to have an element available is popped.
`timeoutSeconds`	Double	Yes	—	Seconds to wait. Use `0` to block indefinitely.

Output

Type: Map<String, String>

A single-entry map where:

Key: The list key that had an element
Value: The popped element

Errors

Error Type	Condition
`REDIS:ARGUMENT`	No keys provided
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	One of the keys is not a list
`REDIS:TIMEOUT`	Timeout reached with no element available

BRPOP

Remove and return the last element from one of multiple lists, blocking until an element is available or timeout occurs.

📘 Redis Reference: BRPOP

XML Example

xml

<lettuce-redis:brpop doc:name="Wait for message"
    config-ref="Redis_Config"
    keys="#[['messages:inbox']]"
    timeoutSeconds="10"/>

Parameters

Parameter	Type	Required	Default	Description
`keys`	List<String>	Yes	—	One or more list keys. At least one required.
`timeoutSeconds`	Double	Yes	—	Seconds to wait. Use `0` to block indefinitely.

Output

Type: Map<String, String>

A single-entry map: the key that had an element and the popped value.

Errors

Error Type	Condition
`REDIS:ARGUMENT`	No keys provided
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	One of the keys is not a list
`REDIS:TIMEOUT`	Timeout reached with no element available

LMOVE

Atomically move an element from one list to another.

📘 Redis Reference: LMOVE

XML Example

xml

<!-- Move task from pending to in-progress queue -->
<lettuce-redis:lmove doc:name="Move task to processing"
    config-ref="Redis_Config"
    source="queue:pending"
    destination="queue:in-progress"
    whereFrom="LEFT"
    whereTo="RIGHT"/>

<!-- payload now contains the moved element -->

Parameters

Parameter	Type	Required	Default	Description
`source`	String	Yes	—	Source list key
`destination`	String	Yes	—	Destination list key
`whereFrom`	ListEnd	Yes	—	Which end to pop from the source list: `LEFT` or `RIGHT`
`whereTo`	ListEnd	Yes	—	Which end to push to the destination list: `LEFT` or `RIGHT`

ListEnd values: LEFT, RIGHT

Output

Type: String (media type: text/plain)

The element that was moved.

Errors

Error Type	Condition
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	Source or destination is not a list

Queue Transfer Pattern

xml

<!-- Implement a reliable queue: move tasks from "pending" to "in-progress" -->
<flow name="process-tasks">
    <scheduler>
        <scheduling-strategy>
            <fixed-frequency frequency="1" timeUnit="SECONDS"/>
        </scheduling-strategy>
    </scheduler>

    <try>
        <lettuce-redis:lmove
            config-ref="Redis_Config"
            source="queue:pending"
            destination="queue:in-progress"
            whereFrom="LEFT"
            whereTo="RIGHT"/>

        <!-- Process the task -->
        <flow-ref name="process-task"/>

        <!-- On success, remove from in-progress -->
        <lettuce-redis:rpop
            config-ref="Redis_Config"
            key="queue:in-progress"/>

        <error-handler>
            <on-error-continue>
                <!-- On failure, move back to pending -->
                <lettuce-redis:lmove
                    config-ref="Redis_Config"
                    source="queue:in-progress"
                    destination="queue:pending"
                    whereFrom="RIGHT"
                    whereTo="LEFT"/>
            </on-error-continue>
        </error-handler>
    </try>
</flow>

BLMOVE

Atomically move an element from one list to another, blocking until an element is available or timeout occurs.

📘 Redis Reference: BLMOVE

XML Example

xml

<lettuce-redis:blmove doc:name="Wait and move task"
    config-ref="Redis_Config"
    source="queue:pending"
    destination="queue:in-progress"
    whereFrom="LEFT"
    whereTo="RIGHT"
    timeout="5.0"/>

Parameters

Parameter	Type	Required	Default	Description
`source`	String	Yes	—	Source list key
`destination`	String	Yes	—	Destination list key
`whereFrom`	ListEnd	Yes	—	Which end to pop from: `LEFT` or `RIGHT`
`whereTo`	ListEnd	Yes	—	Which end to push to: `LEFT` or `RIGHT`
`timeout`	Double	Yes	—	Seconds to wait for an element. Use `0.0` to block indefinitely.

Output

Type: String (media type: text/plain)

The element that was moved.

Errors

Error Type	Condition
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	Source or destination is not a list

LSET

Set the value of an element in a list by its index.

📘 Redis Reference: LSET

XML Example

xml

<!-- Update the first element (index 0) -->
<lettuce-redis:lset doc:name="Update first item"
    config-ref="Redis_Config"
    key="todo:items"
    index="0"
    element="Buy groceries (URGENT)"/>

<!-- Update the last element (index -1) -->
<lettuce-redis:lset doc:name="Update last item"
    config-ref="Redis_Config"
    key="todo:items"
    index="-1"
    element="Call mom"/>

Parameters

Parameter	Type	Required	Default	Description
`key`	String	Yes	—	The list key
`index`	Long	Yes	—	Index of the element to set (0-based). Negative indices count from the end (-1 is last element).
`element`	String	Yes	—	The new value (payload by default via `@Content`)

Output

Type: Void

Errors

Error Type	Condition
`REDIS:OUT_OF_RANGE`	Index is out of range for the list
`REDIS:COMMAND`	General command execution error
`REDIS:WRONG_TYPE`	Key exists but is not a list

List Commands ​

LPUSH ​

XML Example ​

Parameters ​

Output ​

Errors ​

RPUSH ​

XML Example ​

Parameters ​

Output ​

Errors ​

LPOP ​

XML Example ​

Parameters ​

Output ​

Errors ​

RPOP ​

XML Example ​

Parameters ​

Output ​

Errors ​

BLPOP ​

XML Example ​

Parameters ​

Output ​

Errors ​

BRPOP ​

XML Example ​

Parameters ​

Output ​

Errors ​

LMOVE ​

XML Example ​

Parameters ​

Output ​

Errors ​

Queue Transfer Pattern ​

BLMOVE ​

XML Example ​

Parameters ​

Output ​

Errors ​

LSET ​

XML Example ​

Parameters ​

Output ​

Errors ​

List Commands

LPUSH

XML Example

Parameters

Output

Errors

RPUSH

XML Example

Parameters

Output

Errors

LPOP

XML Example

Parameters

Output

Errors

RPOP

XML Example

Parameters

Output

Errors

BLPOP

XML Example

Parameters

Output

Errors

BRPOP

XML Example

Parameters

Output

Errors

LMOVE

XML Example

Parameters

Output

Errors

Queue Transfer Pattern

BLMOVE

XML Example

Parameters

Output

Errors

LSET

XML Example

Parameters

Output

Errors