feat(debugger): implement intelligent snapshot pruning for oversized payloads

integration-tests/debugger/snapshot-pruning.spec.js

@@ -1,6 +1,7 @@
 'use strict'
 
-const { assert } = require('chai')
+const assert = require('node:assert/strict')
+
 const { setup } = require('./utils')
 
 describe('Dynamic Instrumentation', function () {
@@ -12,14 +13,12 @@ describe('Dynamic Instrumentation', function () {
 
       it('should prune snapshot if payload is too large', function (done) {
         t.agent.on('debugger-input', ({ payload: [payload] }) => {
-          assert.isBelow(Buffer.byteLength(JSON.stringify(payload)), 1024 * 1024) // 1MB
-          assert.notProperty(payload.debugger.snapshot, 'captures')
-          assert.strictEqual(
-            payload.debugger.snapshot.captureError,
-            'Snapshot was too large (max allowed size is 1 MiB). ' +
-            'Consider reducing the capture depth or turn off "Capture Variables" completely, ' +
-            'and instead include the variables of interest directly in the message template.'
-          )
+          const payloadSize = Buffer.byteLength(JSON.stringify(payload))
+          assert.ok(payloadSize < 1024 * 1024) // 1MB
+
+          const capturesJson = JSON.stringify(payload.debugger.snapshot.captures)
+          assert.ok(capturesJson.includes('"pruned":true'))
+
           done()
         })
 

packages/dd-trace/src/debugger/devtools_client/send.js

@@ -10,6 +10,7 @@ const { GIT_COMMIT_SHA, GIT_REPOSITORY_URL } = require('../../plugins/util/tags'
 const log = require('./log')
 const { version } = require('../../../../../package.json')
 const { getEnvironmentVariable } = require('../../config-helper')
+const { pruneSnapshot } = require('./snapshot-pruner')
 
 module.exports = send
 
@@ -55,14 +56,23 @@ function send (message, logger, dd, snapshot) {
   let size = Buffer.byteLength(json)
 
   if (size > MAX_LOG_PAYLOAD_SIZE_BYTES) {
-    // TODO: This is a very crude way to handle large payloads. Proper pruning will be implemented later (DEBUG-2624)
-    delete payload.debugger.snapshot.captures
-    payload.debugger.snapshot.captureError =
-      `Snapshot was too large (max allowed size is ${MAX_LOG_PAYLOAD_SIZE_MB} MiB). ` +
-      'Consider reducing the capture depth or turn off "Capture Variables" completely, ' +
-      'and instead include the variables of interest directly in the message template.'
-    json = JSON.stringify(payload)
-    size = Buffer.byteLength(json)
+    let pruned
+    try {
+      pruned = pruneSnapshot(json, size, MAX_LOG_PAYLOAD_SIZE_BYTES)
+    } catch (err) {
+      log.error('[debugger:devtools_client] Error pruning snapshot', err)
+    }
+
+    if (pruned) {
+      json = pruned
+      size = Buffer.byteLength(json)
+    } else {
+      // Fallback if pruning fails
+      const line = Object.keys(snapshot.captures.lines)[0]
+      snapshot.captures.lines[line] = { pruned: true }
+      json = JSON.stringify(payload)
+      size = Buffer.byteLength(json)
+    }
   }
 
   jsonBuffer.write(json, size)