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Cross task execution

A common pattern in compose apps is to trigger tasks from other tasks. This can be done either by creating an HTTP trigger and calling it with fetch(), or by using callTask(). Typically you’ll want to use callTask(). callTask invokes another task in the same compose app. It awaits the invoked task’s main() function and resolves with its return value. If the invoked task throws, the error is re-thrown in the caller. 
callTask<Args = Record<string, unknown>, T = unknown>(
  taskName: string,
  args: Args,
  retryConfig?: {
    max_attempts: number;
    initial_interval_ms: number;
    backoff_factor: number;
  },
): Promise<T>
  • taskName — the name of a task declared in compose.yaml.
  • args — a JSON-serializable payload passed to the invoked task’s main() as its payload argument.
  • retryConfig — optional. Overrides the invoked task’s retry settings for this call.

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Basic Example

import { TaskContext } from "compose";

export async function main({ callTask }: TaskContext) {
  const result = await callTask("my_task", { some: "payload" });
  return result;
}

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Examples

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Call task in a loop

import { TaskContext } from "compose";

type MarketData = {
  questionId: string;
  resolved: boolean;
  startTime: number;
  endTime: number;
};

export async function main({ collection, callTask }: TaskContext) {
  const marketsCollection = await collection<MarketData>("markets");
  const unresolvedMarkets = await marketsCollection.findMany({ resolved: false });

  const SYMBOL = "ETH-USD";

  const marketDataPromises = unresolvedMarkets.map(async (market) => {
    try {
      const response = await callTask<{ error?: string }>("readMarketData", {
        questionId: market.questionId,
        symbol: SYMBOL,
        startTime: market.startTime,
        endTime: market.endTime,
      });

      return {
        market,
        marketData: response,
      };
    } catch (error) {
      console.log(`Failed to read candle data for market ${market.questionId}: ${error}`);
      return null;
    }
  });

  const marketDataResults = await Promise.all(marketDataPromises);

  return {
    marketDataResults,
  };
}

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Next Steps

Task Triggers

Trigger tasks from cron, the CLI and via HTTP

Using Packages

You can use any sandbox compatible typescript packages with any package manager.