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node.jsazuredockerprofiling

Node.js --cpu-prof flag: Failed to convert CPU profile message to V8 string

I'm using the --cpu-prof flag to generate a cpuprofile of my Node.js 18.16.0 application. When I try to initiate the creation of the cpuprofile, I get this error: Failed to convert CPU profile message to V8 string.

I'm hosting my app in a Docker container within Azure App Service. This error hasn't appeared anywhere else on the Internet - What does it mean, and how can I resolve it?

Dockerfile:

FROM node:18-alpine AS builder
WORKDIR /build

COPY . .

RUN npm ci

RUN npm run compile

CMD ["npm", "start"]
Solution

  • If you are running the Node app in Docker container, to use --cpu-prof you need to give the command in the Dockerfile.

    This worked for me:

    I am using a simple node express app.

    Dockerfile:

    FROM  node:lts-alpine

ENV  NODE_ENV=production

WORKDIR  /usr/src/app

COPY  ["package.json",  "package-lock.json*",  "npm-shrinkwrap.json*",  "./"]

RUN  npm  install  --production  --silent  &&  mv  node_modules  ../

COPY  .  .

EXPOSE  3000

RUN  chown  -R  node  /usr/src/app

USER  node

CMD  ["node","--cpu-prof","--prof",  "app.js"]

    OUTPUT:

    I am able to see my cpu profile file inside the container

    To access file use this commands:

    open interactive cell:

    docker exec -it <container_name_or_id> sh

    To Copy the file from container you can run this command

    docker cp 938843ef2767:/usr/src/app/isolate-0x7fdafe318690-1-v8.log .

    Note : used . for copying to current folder.

    EDIT:

    To check the files in Azure follow the following steps:

    • Create Azure Container Registry and push the docker image to registry.

    • Open your Container registry, Go to -> Access Key and enable Admin user
    • Create a Container Instance and select Container registry and select your Image to run the image in container.
    • Open Container Instance, Go to -> Containers->Connect->/bin/sh for Linux.