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Actions

Actions can call third party services to do things such as processing a payment with Stripe. They can be run in Convex's JavaScript environment or in Node.js. They can interact with the database indirectly by calling queries and mutations.

Example: GIPHY Action

Action names​

Actions follow the same naming rules as queries, see Query names.

The action constructor​

To declare an action in Convex you use the action constructor function. Pass it an object with a handler function, which performs the action:

convex/myFunctions.ts
TS
import { action } from "./_generated/server";

export const doSomething = action({
  handler: () => {
    // implementation goes here

    // optionally return a value
    return "success";
  },
});

Unlike a query, an action can but does not have to return a value.

Action arguments and responses​

Action arguments and responses follow the same rules as mutations:

convex/myFunctions.ts
TS
import { action } from "./_generated/server";
import { v } from "convex/values";

export const doSomething = action({
  args: { a: v.number(), b: v.number() },
  handler: (_, args) => {
    // do something with `args.a` and `args.b`

    // optionally return a value
    return "success";
  },
});

The first argument to the handler function is reserved for the action context.

Action context​

The action constructor enables interacting with the database, and other Convex features by passing an ActionCtx object to the handler function as the first argument:

convex/myFunctions.ts
TS
import { action } from "./_generated/server";
import { v } from "convex/values";

export const doSomething = action({
  args: { a: v.number(), b: v.number() },
  handler: (ctx, args) => {
    // do something with `ctx`
  },
});

Which part of that action context is used depends on what your action needs to do:

  • To read data from the database use the runQuery field, and call a query that performs the read:

    convex/myFunctions.ts
    TS
    import { action, internalQuery } from "./_generated/server";
    import { internal } from "./_generated/api";
    import { v } from "convex/values";

    export const doSomething = action({
      args: { a: v.number() },
      handler: async (ctx, args) => {
        const data = await ctx.runQuery(internal.myFunctions.readData, {
          a: args.a,
        });
        // do something with `data`
      },
    });

    export const readData = internalQuery({
      args: { a: v.number() },
      handler: async (ctx, args) => {
        // read from `ctx.db` here
      },
    });

    Here readData is an internal query because we don't want to expose it to the client directly. Actions, mutations and queries can be defined in the same file.

  • To write data to the database use the runMutation field, and call a mutation that performs the write:

    convex/myFunctions.ts
    TS
    import { v } from "convex/values";
    import { action } from "./_generated/server";
    import { internal } from "./_generated/api";

    export const doSomething = action({
      args: { a: v.number() },
      handler: async (ctx, args) => {
        const data = await ctx.runMutation(internal.myMutations.writeData, {
          a: args.a,
        });
        // do something else, optionally use `data`
      },
    });

    Use an internal mutation when you want to prevent users from calling the mutation directly.

    As with queries, it's often convenient to define actions and mutations in the same file.

  • To generate upload URLs for storing files use the storage field. Read on about File Storage.

  • To check user authentication use the auth field. Auth is propagated automatically when calling queries and mutations from the action. Read on about Authentication.

  • To schedule functions to run in the future, use the scheduler field. Read on about Scheduled Functions.

  • To search a vector index, use the vectorSearch field. Read on about Vector Search.

Calling third-party APIs and using NPM packages​

Actions can run in Convex's custom JavaScript environment or in Node.js.

By default, actions run in Convex's environment. This environment supports fetch, so actions that simply want to call a third-party API using fetch can be run in this environment:

convex/myFunctions.ts
TS
import { action } from "./_generated/server";

export const doSomething = action({
  args: {},
  handler: async () => {
    const data = await fetch("https://api.thirdpartyservice.com");
    // do something with data
  },
});

Actions running in Convex's environment are faster compared to Node.js, since they don't require extra time to start up before running your action (cold starts). They can also be defined in the same file as other Convex functions. Like queries and mutations they can import NPM packages, but not all are supported.

Actions needing unsupported NPM packages or Node.js APIs can be configured to run in Node.js by adding the "use node" directive at the top of the file. Note that other Convex functions cannot be defined in files with the "use node"; directive.

convex/myAction.ts
TS
"use node";

import { action } from "./_generated/server";
import SomeNpmPackage from "some-npm-package";

export const doSomething = action({
  args: {},
  handler: () => {
    // do something with SomeNpmPackage
  },
});

Learn more about the two Convex Runtimes.

Calling actions from clients​

To call an action from React use the useAction hook along with the generated api object.

src/myApp.tsx
TS
import React from "react";
import { useAction } from "convex/react";
import { api } from "../convex/_generated/api";

export function MyApp() {
  const performMyAction = useAction(api.myFunctions.doSomething);
  const handleClick = () => {
    performMyAction({ a: 1 });
  };
  // pass `handleClick` to a button
  // ...
}

See the React client documentation for all the ways queries can be called.

Unlike mutations, actions from a single client are parallelized. Each action will be executed as soon as it reaches the server (even if other actions and mutations from the same client are running).

If your app relies on actions running after other actions or mutations make sure to only trigger the action after the relevant previous function completes.

Limits​

Actions time out after 10 minutes. Node.js and Convex runtime have 512MB and 64MB memory limit respectively. Please contact us if you have a use case that requires configuring higher limits.

Actions can do up to 1000 concurrent operations, such as executing queries, mutations or performing fetch requests.

Error handling​

Unlike queries and mutations, actions may have side-effects and therefore can't be automatically retried by Convex when errors occur. For example, say your action calls Stripe to send a customer invoice. If the HTTP request fails, Convex has no way of knowing if the invoice was already sent. Like in normal backend code, it is the responsibility of the caller to handle errors raised by actions and retry the action call if appropriate.

Dangling promises​

Make sure to await all promises created within an action. Async tasks still running when the function returns might or might not complete. In addition, since the Node.js execution environment might be reused between action calls, dangling promises might result in errors in subsequent action invocations.