Isolate and context re-use.

packages/backend-core/src/context/types.ts

@@ -1,5 +1,5 @@
 import { IdentityContext } from "@budibase/types"
-import { ExecutionTimeTracker } from "../timers"
+import { Isolate, Context } from "isolated-vm"
 
 // keep this out of Budibase types, don't want to expose context info
 export type ContextMap = {
@@ -10,5 +10,6 @@ export type ContextMap = {
   isScim?: boolean
   automationId?: string
   isMigrating?: boolean
-  jsExecutionTracker?: ExecutionTimeTracker
+  jsIsolate: Isolate
+  jsContext: Context
 }

packages/backend-core/src/timers/timers.ts

@@ -20,41 +20,3 @@ export function cleanup() {
   }
   intervals = []
 }
-
-export class ExecutionTimeoutError extends Error {
-  public readonly name = "ExecutionTimeoutError"
-}
-
-export class ExecutionTimeTracker {
-  static withLimit(limitMs: number) {
-    return new ExecutionTimeTracker(limitMs)
-  }
-
-  constructor(readonly limitMs: number) {}
-
-  private totalTimeMs = 0
-
-  track<T>(f: () => T): T {
-    this.checkLimit()
-    const start = process.hrtime.bigint()
-    try {
-      return f()
-    } finally {
-      const end = process.hrtime.bigint()
-      this.totalTimeMs += Number(end - start) / 1e6
-      this.checkLimit()
-    }
-  }
-
-  get elapsedMS() {
-    return this.totalTimeMs
-  }
-
-  checkLimit() {
-    if (this.totalTimeMs > this.limitMs) {
-      throw new ExecutionTimeoutError(
-        `Execution time limit of ${this.limitMs}ms exceeded: ${this.totalTimeMs}ms`
-      )
-    }
-  }
-}

packages/server/src/jsRunner.ts

@@ -1,76 +1,41 @@
 import ivm from "isolated-vm"
 import env from "./environment"
 import { setJSRunner } from "@budibase/string-templates"
-import { context, timers } from "@budibase/backend-core"
+import { context } from "@budibase/backend-core"
 import tracer from "dd-trace"
+import { readFileSync } from "fs"
 
-type TrackerFn = <T>(f: () => T) => T
+const helpersSource = readFileSync(
+  "node_modules/@budibase/string-templates/dist/bundle.mjs",
+  "utf8"
+)
 
 export function init() {
   setJSRunner((js: string, ctx: Record<string, any>) => {
     return tracer.trace("runJS", {}, span => {
-      const perRequestLimit = env.JS_PER_REQUEST_TIME_LIMIT_MS
+      const bbCtx = context.getCurrentContext()!
-      let track: TrackerFn = f => f()
+      if (!bbCtx.jsIsolate) {
-      if (perRequestLimit) {
+        bbCtx.jsIsolate = new ivm.Isolate({ memoryLimit: 64 })
-        const bbCtx = tracer.trace("runJS.getCurrentContext", {}, span =>
+        bbCtx.jsContext = bbCtx.jsIsolate.createContextSync()
-          context.getCurrentContext()
+        const helpersModule = bbCtx.jsIsolate.compileModuleSync(helpersSource)
-        )
+        helpersModule.instantiateSync(bbCtx.jsContext, () => {
-        if (bbCtx) {
+          throw new Error("No imports allowed")
-          if (!bbCtx.jsExecutionTracker) {
-            span?.addTags({
-              createdExecutionTracker: true,
-            })
-            bbCtx.jsExecutionTracker = tracer.trace(
-              "runJS.createExecutionTimeTracker",
-              {},
-              span => timers.ExecutionTimeTracker.withLimit(perRequestLimit)
-            )
-          }
-          span?.addTags({
-            js: {
-              limitMS: bbCtx.jsExecutionTracker.limitMs,
-              elapsedMS: bbCtx.jsExecutionTracker.elapsedMS,
-            },
-          })
-          // We call checkLimit() here to prevent paying the cost of creating
-          // a new VM context below when we don't need to.
-          tracer.trace("runJS.checkLimitAndBind", {}, span => {
-            bbCtx.jsExecutionTracker!.checkLimit()
-            track = bbCtx.jsExecutionTracker!.track.bind(
-              bbCtx.jsExecutionTracker
-            )
-          })
-        }
-      }
-
-      const isolate = new ivm.Isolate({ memoryLimit: 64 })
-      const vm = isolate.createContextSync()
-      const jail = vm.global
-      jail.setSync("global", jail.derefInto())
-
-      for (let key in ctx) {
-        let value
-        if (["alert", "setInterval", "setTimeout"].includes(key)) {
-          value = undefined
-        } else {
-          value = ctx[key]
-        }
-
-        if (typeof value === "function") {
-          js = value.toString() + "\n" + js
-          continue
-        } else {
-          value = new ivm.ExternalCopy(value).copyInto({ release: true })
-        }
-        jail.setSync(key, value)
-      }
-
-      const script = isolate.compileScriptSync(js)
-
-      return track(() => {
-        return script.runSync(vm, {
-          timeout: env.JS_PER_EXECUTION_TIME_LIMIT_MS,
         })
+      }
+
+      const perRequestLimit = env.JS_PER_REQUEST_TIME_LIMIT_MS
+      if (perRequestLimit) {
+        const cpuMs = Number(bbCtx.jsIsolate.cpuTime) / 1e6
+        if (cpuMs > perRequestLimit) {
+          throw new Error(
+            `CPU time limit exceeded (${cpuMs}ms > ${perRequestLimit}ms)`
+          )
+        }
+      }
+
+      const script = bbCtx.jsIsolate.compileScriptSync(js)
+      return script.runSync(bbCtx.jsContext, {
+        timeout: env.JS_PER_EXECUTION_TIME_LIMIT_MS,
       })
     })
   })