bcrypt and Docker bcrypt_lib.node: invalid ELF header

Question

I've seen several questions regarding macOS, Docker and bcrypt on Node.js. This seems the closest answer to my problem but it didn't work.

My Dockerfile:

FROM node:6.4.0

COPY . /app
RUN ls -la /app
WORKDIR /app

RUN cd /app; npm install
CMD ["node", "index.js"]

My .dockerignore file:

node_modules

My package.json dependencies:

"dependencies": {
  "bcrypt": "1.0.0",
}

When starting the container, I get this error:

/app/node_modules/bcrypt/build/Release/bcrypt_lib.node: invalid ELF header

From the ls -la /app command in the Dockerfile I can see that the node_modules folder definitely isn't copied from the host (macOS):

drwxr-xr-x  6 root root  4096 Dec  7 21:29 .
drwxr-xr-x 47 root root  4096 Dec  7 21:29 ..
-rw-r--r--  1 root root   763 Dec  7 20:55 .dockerignore
-rw-r--r--  1 root root   122 Dec  7 21:18 Dockerfile
rw-r--r--  1 root root 13525 Dec  7 19:43 index.js
-rw-r--r--  1 root root   947 Dec  7 21:28 package.json

The bcrypt npm install log:

> [email protected] install /app/node_modules/bcrypt
> node-pre-gyp install --fallback-to-build

node-pre-gyp info it worked if it ends with ok
node-pre-gyp info using [email protected]
node-pre-gyp info using [email protected] | linux | x64
node-pre-gyp info check checked for "/app/node_modules/bcrypt/lib/binding/bcrypt_lib.node" (not found)
node-pre-gyp http GET https://github.com/kelektiv/node.bcrypt.js/releases/download/v1.0.0/bcrypt_lib-v1.0.0-node-v48-linux-x64.tar.gz
node-pre-gyp http 404 https://github.com/kelektiv/node.bcrypt.js/releases/download/v1.0.0/bcrypt_lib-v1.0.0-node-v48-linux-x64.tar.gz
node-pre-gyp ERR! Tried to download: https://github.com/kelektiv/node.bcrypt.js/releases/download/v1.0.0/bcrypt_lib-v1.0.0-node-v48-linux-x64.tar.gz
node-pre-gyp ERR! Pre-built binaries not found for [email protected] and [email protected] (node-v48 ABI) (falling back to source compile with node-gyp)
node-pre-gyp http Pre-built binary not available for your system, looked for https://github.com/kelektiv/node.bcrypt.js/releases/download/v1.0.0/bcrypt_lib-v1.0.0-node-v48-linux-x64.tar.gz
gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | linux | x64
gyp info ok
gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | linux | x64
gyp info spawn /usr/bin/python2
gyp info spawn args [ '/usr/local/lib/node_modules/npm/node_modules/node-gyp/gyp/gyp_main.py',
gyp info spawn args   'binding.gyp',
gyp info spawn args   '-f',
gyp info spawn args   'make',
gyp info spawn args   '-I',
gyp info spawn args   '/app/node_modules/bcrypt/build/config.gypi',
gyp info spawn args   '-I',
gyp info spawn args   '/usr/local/lib/node_modules/npm/node_modules/node-gyp/addon.gypi',
gyp info spawn args   '-I',
gyp info spawn args   '/root/.node-gyp/6.4.0/include/node/common.gypi',
gyp info spawn args   '-Dlibrary=shared_library',
gyp info spawn args   '-Dvisibility=default',
gyp info spawn args   '-Dnode_root_dir=/root/.node-gyp/6.4.0',
gyp info spawn args   '-Dnode_gyp_dir=/usr/local/lib/node_modules/npm/node_modules/node-gyp',
gyp info spawn args   '-Dnode_lib_file=node.lib',
gyp info spawn args   '-Dmodule_root_dir=/app/node_modules/bcrypt',
gyp info spawn args   '--depth=.',
gyp info spawn args   '--no-parallel',
gyp info spawn args   '--generator-output',
gyp info spawn args   'build',
gyp info spawn args   '-Goutput_dir=.' ]
gyp info ok
gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | linux | x64
gyp info spawn make
gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
make: Entering directory '/app/node_modules/bcrypt/build'
  CXX(target) Release/obj.target/bcrypt_lib/src/blowfish.o
  CXX(target) Release/obj.target/bcrypt_lib/src/bcrypt.o
  CXX(target) Release/obj.target/bcrypt_lib/src/bcrypt_node.o
  SOLINK_MODULE(target) Release/obj.target/bcrypt_lib.node
  COPY Release/bcrypt_lib.node
  COPY /app/node_modules/bcrypt/lib/binding/bcrypt_lib.node
  TOUCH Release/obj.target/action_after_build.stamp
make: Leaving directory '/app/node_modules/bcrypt/build'
gyp info ok
node-pre-gyp info ok

Update: I tried to run bcrypt inside the container which seems to work fine:

docker run identity file /app/node_modules/bcrypt/build/Release/bcrypt_lib.node
/app/node_modules/bcrypt/build/Release/bcrypt_lib.node: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=2a9d4a04f6f9c548f8035b9b737c1efac5d774d2, not stripped

Answer 1

The comment from Stefan Scherer has shown that my code in the question is valid and should work and made me search for other causes of the problem.

In the end I found out that it is caused by the docker-compose.yml which started the container as part of multiple services.

The problem was caused by this volume entry for the container:

volumes :
- ../identity/:/app

Thus the node_modules folder from the host again is mapped into the container and the bcrypt ELF header is indeed invalid again.

The solution is to exclude the node_modules folder from the mapping (as also explained here):

volumes :
    /app/node_modules/

Answer 2

I have found that excluding the entire local node_modules directory does not allow you to install npm packages and have your docker container track those changes in the container on the fly. In order to have other package changes tracked specify only the bcrypt directory in the container volume:

volumes: 
  - .:/app
  - /app/node_modules/bcrypt/