lib,src,doc: add --heapsnapshot-signal CLI flag

This flag allows heap snapshots to be captured without
modifying application code.

PR-URL: https://github.com/nodejs/node/pull/27133
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/internal/bootstrap/pre_execution.js b/lib/internal/bootstrap/pre_execution.js
index e2b1103f8c..6b1e3fb213 100644
--- a/lib/internal/bootstrap/pre_execution.js
+++ b/lib/internal/bootstrap/pre_execution.js
@@ -29,6 +29,8 @@ function prepareMainThreadExecution(expandArgv1 = false) {
   initializeReport();
   initializeReportSignalHandlers();  // Main-thread-only.
 
+  initializeHeapSnapshotSignalHandlers();
+
   // If the process is spawned with env NODE_CHANNEL_FD, it's probably
   // spawned by our child_process module, then initialize IPC.
   // This attaches some internal event listeners and creates:
@@ -166,6 +168,20 @@ function initializeReportSignalHandlers() {
   addSignalHandler();
 }
 
+function initializeHeapSnapshotSignalHandlers() {
+  const signal = getOptionValue('--heapsnapshot-signal');
+
+  if (!signal)
+    return;
+
+  require('internal/validators').validateSignalName(signal);
+  const { writeHeapSnapshot } = require('v8');
+
+  process.on(signal, () => {
+    writeHeapSnapshot();
+  });
+}
+
 function setupTraceCategoryState() {
   const { isTraceCategoryEnabled } = internalBinding('trace_events');
   const { toggleTraceCategoryState } = require('internal/process/per_thread');