Context, Railway Error and Task

Data Context is an object injected into logic functions at runtime, which containes some key components:

• Task and execution-related information
• Trigger payload

Availability

• ✓ Generic logic
• ✓ Aggregator logic

Context

Type:

• GenericContext (generic logic)
• AggregatorContext (aggregator logic)

When a logic gets executed, a data context object ctx will be available in both run and handleError functions:

Member	Type	Description
task	Task	Return task object. See Task
async payload()	Promise<Payload>	Return trigger metadata and payload. See Payload

JavaScript

export async function run(ctx) {
    // ctx is the data context
}

export async function handleError(ctx, error) {
    // the same context as well as error
}

TypeScript

import { GenericContext, RailwayError } from "@fstnetwork/loc-logic-sdk";

export async function run(ctx: GenericContext) {
    // ctx is the data context
}

export async function handleError(ctx: GenericContext, error: RailwayError) {
    // ctx and railway error for error handling
}

Railway Error

Type: RailwayError

RailwayError is a object extended from the JavaScript Error class, which will be passed to handleError() upon an error occurred:

export async function handleError(ctx, error) {
    // ...
    const errorMessage = error.message; // error message
    const errorLogicId = error.logicPermanentIdentity; // the PID of the logic that have error occurred
}

Member	Type	Description
name	string	Error name
message	string	Error message
stack	string	Error stack trace
logicPermanentIdentity	string	Logic PID where the error originated
logicRevision	number	Revision of the logic where the error originated

See Tips on Error Handling for details on logic error handling.

note

If an error was thrown from LOC runtime (for example, from one of the agents), the stack trace would come from LOC core instead of the logic code.

Task

Type: Task

export async function run(ctx) {
    const task = ctx.task;
}

A task is an execution of a data process invoked by a trigger. The task object is lazy-loaded and includes the following metadata:

Member	Type	Description
taskKey	TaskKey, which is { taskId: string, executionId: string }	Task ID and execution ID
startTimestamp	Date	Task start datetime
dataProcess	VersionedIdentityContext	Data process permanent ID
currentLogic?	VersionedIdentityContext	Current logic permanent ID
executedLogics	Array<VersionedIdentityContext>	An array of identity of executed logic

Versioned Identity Context

Represents the identity of a logic or a data process:

Member	Type	Description
name	string	Name
permanentIdentity	string	Permanent identity string (PID)
revision	number	Revision number

Example

const taskId = ctx.task.taskKey.taskId;
const executionId = ctx.task.taskKey.executionId;

const dpPid = ctx.task.dataProcess.permanentIdentity;
const logicPid = ctx.task.currentLogic.permanentIdentity;