Heap Out of Memory Error While Running Python Application

I have deployed a Python Flask application using PM2. The deployment works smoothly under light traffic, but when the application experiences 10-15 concurrent users running heavier workloads, the PM2 service crashes. However, the underlying Python process continues to run.

Can anyone advise on the potential causes of this issue and suggest how I can prevent it from recurring?

Supporting information

Error from pm2.log

<--- JS stacktrace --->

FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
----- Native stack trace -----

 1: 0xca5430 node::Abort() [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 2: 0xb7807d  [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 3: 0xeca0b0 v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 4: 0xeca397 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 5: 0x10dc0e5  [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 6: 0x10f3f68 v8::internal::Heap::CollectGarbage(v8::internal::AllocationSpace, v8::internal::GarbageCollectionReason, v8::GCCallbackFlags) [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 7: 0x114cb3c v8::internal::MinorGCJob::Task::RunInternal() [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 8: 0xd201a6  [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
 9: 0xd22d5f node::PerIsolatePlatformData::FlushForegroundTasksInternal() [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
10: 0x188aa33  [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
11: 0x189f41b  [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
12: 0x188b757 uv_run [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
13: 0xbbbb83 node::SpinEventLoopInternal(node::Environment*) [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
14: 0xcf4d25  [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
15: 0xcf56ed node::NodeMainInstance::Run() [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
16: 0xc5f367 node::Start(int, char**) [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
17: 0x7f350ae3feb0  [/lib64/libc.so.6]
18: 0x7f350ae3ff60 __libc_start_main [/lib64/libc.so.6]
19: 0xbb8d7e _start [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
2024-09-26T14:23:21: PM2 log: ===============================================================================
2024-09-26T14:23:21: PM2 log: --- New PM2 Daemon started ----------------------------------------------------
2024-09-26T14:23:21: PM2 log: Time                 : Thu Sep 26 2024 14:23:21 GMT+0000 (Coordinated Universal Time)
2024-09-26T14:23:21: PM2 log: PM2 version          : 5.4.2
2024-09-26T14:23:21: PM2 log: Node.js version      : 20.11.0
2024-09-26T14:23:21: PM2 log: Current arch         : x64
2024-09-26T14:23:21: PM2 log: PM2 home             : /home/ec2-user/.pm2
2024-09-26T14:23:21: PM2 log: PM2 PID file         : /home/ec2-user/.pm2/pm2.pid
2024-09-26T14:23:21: PM2 log: RPC socket file      : /home/ec2-user/.pm2/rpc.sock
2024-09-26T14:23:21: PM2 log: BUS socket file      : /home/ec2-user/.pm2/pub.sock
2024-09-26T14:23:21: PM2 log: Application log path : /home/ec2-user/.pm2/logs
2024-09-26T14:23:21: PM2 log: Worker Interval      : 30000
2024-09-26T14:23:21: PM2 log: Process dump file    : /home/ec2-user/.pm2/dump.pm2
2024-09-26T14:23:21: PM2 log: Concurrent actions   : 2
2024-09-26T14:23:21: PM2 log: SIGTERM timeout      : 1600
2024-09-26T14:23:21: PM2 log: ===============================================================================

PM2 Report

--- PM2 report ----------------------------------------------------------------
Date                 : Thu Sep 26 2024 14:49:48 GMT+0000 (Coordinated Universal Time)
===============================================================================
--- Daemon -------------------------------------------------
pm2d version         : 5.4.2
node version         : 20.11.0
node path            : /home/ec2-user/.nvm/versions/node/v20.11.0/bin/pm2
argv                 : /home/ec2-user/.nvm/versions/node/v20.11.0/bin/node,/home/ec2-user/.nvm/versions/node/v20.11.0/lib/node_modules/pm2/lib/Daemon.js
argv0                : node
user                 : ec2-user
uid                  : 1000
gid                  : 1000
uptime               : 26min
===============================================================================
--- CLI ----------------------------------------------------
local pm2            : 5.4.2
node version         : 20.11.0
node path            : /home/ec2-user/.nvm/versions/node/v20.11.0/bin/pm2
argv                 : /home/ec2-user/.nvm/versions/node/v20.11.0/bin/node,/home/ec2-user/.nvm/versions/node/v20.11.0/bin/pm2,report
argv0                : node
user                 : ec2-user
uid                  : 1000
gid                  : 1000
===============================================================================
--- System info --------------------------------------------
arch                 : x64
platform             : linux
type                 : Linux
cpus                 : Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz
cpus nb              : 4
freemem              : 14047399936
totalmem             : 16758525952
home                 : /home/ec2-user
===============================================================================
--- PM2 list -----------------------------------------------
┌────┬───────────┬─────────────┬─────────┬─────────┬──────────┬────────┬──────┬───────────┬──────────┬──────────┬──────────┬──────────┐
│ id │ name      │ namespace   │ version │ mode    │ pid      │ uptime │ ↺    │ status    │ cpu      │ mem      │ user     │ watching │
└────┴───────────┴─────────────┴─────────┴─────────┴──────────┴────────┴──────┴───────────┴──────────┴──────────┴──────────┴──────────┘
[PM2][WARN] Current process list is not synchronized with saved list. App cdr differs. Type 'pm2 save' to synchronize.
===============================================================================
--- Daemon logs --------------------------------------------
/home/ec2-user/.pm2/pm2.log last 20 lines:
PM2        | 16: 0xc5f367 node::Start(int, char**) [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
PM2        | 17: 0x7f350ae3feb0  [/lib64/libc.so.6]
PM2        | 18: 0x7f350ae3ff60 __libc_start_main [/lib64/libc.so.6]
PM2        | 19: 0xbb8d7e _start [PM2 v5.4.2: God Daemon (/home/ec2-user/.pm2)]
PM2        | 2024-09-26T14:23:21: PM2 log: ===============================================================================
PM2        | 2024-09-26T14:23:21: PM2 log: --- New PM2 Daemon started ----------------------------------------------------
PM2        | 2024-09-26T14:23:21: PM2 log: Time                 : Thu Sep 26 2024 14:23:21 GMT+0000 (Coordinated Universal Time)
PM2        | 2024-09-26T14:23:21: PM2 log: PM2 version          : 5.4.2
PM2        | 2024-09-26T14:23:21: PM2 log: Node.js version      : 20.11.0
PM2        | 2024-09-26T14:23:21: PM2 log: Current arch         : x64
PM2        | 2024-09-26T14:23:21: PM2 log: PM2 home             : /home/ec2-user/.pm2
PM2        | 2024-09-26T14:23:21: PM2 log: PM2 PID file         : /home/ec2-user/.pm2/pm2.pid
PM2        | 2024-09-26T14:23:21: PM2 log: RPC socket file      : /home/ec2-user/.pm2/rpc.sock
PM2        | 2024-09-26T14:23:21: PM2 log: BUS socket file      : /home/ec2-user/.pm2/pub.sock
PM2        | 2024-09-26T14:23:21: PM2 log: Application log path : /home/ec2-user/.pm2/logs
PM2        | 2024-09-26T14:23:21: PM2 log: Worker Interval      : 30000
PM2        | 2024-09-26T14:23:21: PM2 log: Process dump file    : /home/ec2-user/.pm2/dump.pm2
PM2        | 2024-09-26T14:23:21: PM2 log: Concurrent actions   : 2
PM2        | 2024-09-26T14:23:21: PM2 log: SIGTERM timeout      : 1600
PM2        | 2024-09-26T14:23:21: PM2 log: ===============================================================================

No source file, test, or entry point is named. Start with the PM2 daemon logs and the reported PM2 5.4.2 and Node.js 20.11.0 environment, then reproduce the failure under concurrent Flask workloads; done means explaining why the PM2 daemon exhausts its heap while the Python process continues and defining a verified prevention or fix.