System variables

System variables are values that Patchworks generates automatically at run time. Unlike flow variables, you don't define them - they're always available, and they're resolved for the specific step and payload being processed at the moment the variable is referenced.

Most system variables are unique to the step and payload being processed. The exception is flow_run_id, which is the same for every step and payload within a single flow run.

Available system variables

Variable	Description
system.variables.payload_id	The unique ID of the payload being processed at the current step
system.variables.flow_run_id	The ID of the current flow run (shared across all steps and payloads in the run)
system.variables.unix_time	The current Unix timestamp, in seconds
system.variables.unix_microtime	The current Unix timestamp, with microsecond precision

Referencing system variables

System variables can be referenced in any variable or parameter field using the syntax below:

{{ system.variables.payload_id }}
{{ system.variables.flow_run_id }}
{{ system.variables.unix_time }}
{{ system.variables.unix_microtime }}

System variables are available in all shapes. For example, they can be:

• Referenced in mappings as custom strings

• Passed as variables in a connector shape

• Accessed directly in the body of an endpoint

System variables can be 'mixed and matched' with payload, metadata and flow variables.

Examples

Passing a system variable as an endpoint variable

In the example below, a connector shape is configured for a Shopify Inventory Adjust Quantities GraphQL endpoint, which expects a Uuid variable. Rather than entering a static value, {{ system.variables.payload_id }} is entered so that each payload processed by the shape is sent with its own unique ID.

Using a system variable to generate an idempotency key

System variables can also be referenced directly in an endpoint body. In the example below, {{ system.variables.payload_id }} is used as the @idempotent key in a Shopify GraphQL mutation. Because the payload ID is unique per payload, this guarantees that the same inventory adjustment is never applied twice if the request is retried:

{"query":"mutation inventoryAdjustQuantitiesWithIdempotency($input: InventoryAdjustQuantitiesInput!) { inventoryAdjustQuantities(input: $input) @idempotent(key: \"{{system.variables.payload_id}}\") { inventoryAdjustmentGroup { createdAt reason referenceDocumentUri changes { name quantityAfterChange delta item { sku variant { id price legacyResourceId product { id totalInventory legacyResourceId }} } } } userErrors { field message } } }",
"variables":{
  "input":{
    "reason":"correction","name":"available","changes":[[payload]]
  }
}}