@memberjunction/action-runtime

@memberjunction/action-runtime

Runtime executor for MJ actions whose Type='Runtime' — the ones whose source code lives in the database (Action.Code) rather than in a compiled @RegisterClass-registered BaseAction subclass.

Ships a single singleton, RuntimeActionExecutor.Instance, that @memberjunction/actions dispatches to when it sees an action with Type='Runtime'. Everything else about the action (approval gate, permission config, input / output param wiring, sandbox isolation) is handled here.

Where it sits in the stack

┌──────────────────────────────────────────────────────────────┐
│ @memberjunction/actions  (ActionEngine)                      │
│   – dispatches Custom/Generated via ClassFactory             │
│   – dispatches Runtime via RuntimeActionExecutor ────────┐   │
└──────────────────────────────────────────────────────────────┘
                                                          │
                           ┌──────────────────────────────┴────┐
                           │ @memberjunction/action-runtime    │
                           │   – approval + status gating      │
                           │   – input/output param mapping    │
                           │   – wraps user code for the vm    │
                           │   – error-type → resultCode       │
                           └──────────────────┬────────────────┘
                                              │
                           ┌──────────────────┴────────────────┐
                           │ @memberjunction/code-execution    │
                           │   – CodeExecutionService          │
                           │   – WorkerPool (forked children)  │
                           │   – isolated-vm sandboxes         │
                           │   – bridge-call IPC protocol      │
                           └───────────────────────────────────┘

This package does not build the utilities.* bridge — that lives in @memberjunction/action-runtime-host and is handed in as a bridgeHandlers map per invocation. RuntimeActionExecutor is the boundary between "action metadata + parameter plumbing" and "isolated-vm sandbox" — it doesn't know or care what utilities.* exposes.

Executor lifecycle

On first invocation, RuntimeActionExecutor.Instance lazily spins up the shared CodeExecutionService — which in turn forks N (default 2) worker processes, loads isolated-vm in each, and warms them for sandbox execution. Because the executor is a BaseSingleton, that setup cost is paid once per MJAPI process; every subsequent Runtime-action invocation reuses the warm pool (typical latency ~80ms vs. ~5s cold start).

See @memberjunction/code-execution README for the worker pool lifecycle, circuit-breaker behavior, and how failed workers are recycled.

What execute() does, in order

• Type gate — refuses anything other than Type='Runtime' with resultCode: INVALID_TYPE.
• Code presence — refuses missing or empty Action.Code with resultCode: MISSING_CODE.
• Status gate — refuses Status !== 'Active' with resultCode: INACTIVE.
• Approval gate — refuses CodeApprovalStatus !== 'Approved' with resultCode: NOT_APPROVED. This is the primary security boundary — an operator must have explicitly approved the code before it can run.
• Abort check — refuses upstream-aborted signals with resultCode: TIMEOUT.
• Input wiring — builds a plain input object from every ActionParam with Type === 'Input' | 'Both', keyed by Name. Output-type params are excluded so user code isn't confused by half-filled output slots.
• Code wrapping — wraps user code so its return value lands in the sandbox's output variable (see "User code contract" below).
• Sandbox dispatch — calls CodeExecutionService.execute({ code, inputData, timeoutSeconds, memoryLimitMB, bridgeHandlers, maxBridgeCalls, abortSignal }). Default limits: 30s wall clock, 128MB heap.
• Result mapping — promotes the returned value into output ActionParams (see "Output params") and maps any errorType the sandbox surfaced into the corresponding RuntimeActionResultCode.

User code contract

User code is written as the body of a function — it receives input, can return any value, and has access to an allowlisted require() for standard libraries (lodash, date-fns, mathjs, papaparse, uuid, validator):

const _ = require('lodash');
const { numbers, outlierThresholdSigma = 2 } = input;

if (!Array.isArray(numbers)) return { success: false, error: 'numbers must be an array' };

const nums = numbers.filter((n) => typeof n === 'number' && Number.isFinite(n));
const mean = _.sum(nums) / nums.length;
const stdDev = Math.sqrt(_.sumBy(nums, (n) => Math.pow(n - mean, 2)) / nums.length);

return {
  success: true,
  count: nums.length,
  mean,
  stdDev,
  outliers: nums.filter((n) => Math.abs(n - mean) > stdDev * outlierThresholdSigma)
};

Under the hood, RuntimeActionExecutor produces a single awaited statement that the worker's outer async wrapper captures correctly:

output = await (async function(input) { /* USER CODE HERE */ })(input);

Why this shape: the worker's outer wrapper looks roughly like (async function() { let output; ${params.code}; globalThis._output = output; })(); — it does not await arbitrary expressions in the user's code. Our single await (...) statement is something the outer wrapper's sequential execution awaits naturally, so the return value flows to the host cleanly. An earlier async-IIFE wrapper inside the user code dropped the return value; the current one-liner form is deliberate.

Output params

When user code returns:

• An object — each top-level key becomes an Output ActionParam. If the key name matches an existing Input param, that param is upgraded to Both and its value is replaced with the returned value.
• A scalar, array, or non-object — wrapped under an Output param named result.
• undefined — no output params added.

Params emitted here are plain objects ({ Name, Value, Type }), not class instances. This is deliberate: MJ's GraphQL resolver runs them through CopyScalarsAndArrays, which silently drops keys whose values are class instances without a toJSON. Emitting plain objects keeps the full output set visible end-to-end.

Approval gate in practice

if (action.CodeApprovalStatus !== 'Approved') {
  return {
    success: false,
    resultCode: RuntimeActionResultCode.NOT_APPROVED,
    message: `Action '${action.Name}' has CodeApprovalStatus='${action.CodeApprovalStatus}'. ` +
             'Runtime actions must be approved before execution.',
    params: originalParams
  };
}

This check runs before any user code executes, before CodeExecutionService.execute() is even called. No sandbox cost is paid for unapproved actions. In MJExplorer, the action form surfaces CodeApprovalStatus prominently and exposes a dropdown for toggling Approved / Pending / Rejected in edit mode.

Result codes

Defined in RuntimeActionResultCode:

Code	Meaning
SUCCESS	User code completed, output captured
INVALID_TYPE	Action.Type !== 'Runtime'
MISSING_CODE	Action.Code null/empty
INACTIVE	Action.Status !== 'Active'
NOT_APPROVED	Action.CodeApprovalStatus !== 'Approved'
TIMEOUT	Upstream abort OR sandbox wall-clock exceeded
MEMORY_LIMIT	Sandbox exceeded memoryLimitMB
SYNTAX_ERROR	User code couldn't be parsed
SECURITY_ERROR	Sandbox detected a policy violation
RUNTIME_ERROR	User code threw
UNEXPECTED_ERROR	Host-side dispatch failure (rare — the sandbox service itself threw)

The utilities.* bridge

User code in Runtime actions has access to MJ services via a utilities.* global — utilities.md.GetEntity, utilities.rv.RunView, utilities.actions.Invoke, utilities.agents.Run, utilities.ai.ExecutePrompt, etc. That bridge is not defined here — it's in @memberjunction/action-runtime-host and is passed in as the bridgeHandlers param per invocation.

The split exists to avoid a circular dependency — see the RuntimeHost README for the full story.

Testing

cd packages/Actions/Runtime
npm run test          # 13 unit tests covering approval gates, param mapping, error paths

End-to-end regression is in packages/Actions/Runtime/harness/run-demos.ts — a standalone tsx script that spins up a real SQL connection, registers the full class graph, and runs all 5 demo Runtime actions (Calculate Array Statistics, Entity Data Quality Report, Find Similar Records, Summarize Entity Records, Weekly Entity Digest) against a live database. Run with:

npx tsx packages/Actions/Runtime/harness/run-demos.ts

Exits 0 if all 5 pass.

Related packages

• @memberjunction/action-runtime-host — the default utilities.* bridge implementation
• @memberjunction/code-execution — isolated-vm sandbox + worker pool
• @memberjunction/actions-base — shared types + the RuntimeActionConfigurationSchema parsed before dispatch
• @memberjunction/actions — ActionEngine that routes Type='Runtime' records here