Windows Docker mongo container doesn't work with volume mount

Question

I have the following docker command

docker run -v //c/data:/data/db mongo

and I get the following error response from docker / mongo

MongoDB starting : pid=1 port=27017 dbpath=/data/db 64-bit host=8706cbf1b78f
db version v3.4.2
git version: 3f76e40c105fc223b3e5aac3e20dcd026b83b38b
OpenSSL version: OpenSSL 1.0.1t  3 May 2016
allocator: tcmalloc
modules: none
build environment:
    distmod: debian81
    distarch: x86_64
    target_arch: x86_64
options: {}
wiredtiger_open config: create,cache_size=478M,session_max=20000,eviction=(threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),checkpoint=(wait=60,log_size=2GB),statistics_log=(wait=0),
WiredTiger error (1) [1489982988:687653][1:0x7fec9df0ccc0], connection: /data/db/WiredTiger.wt: handle-open: open: Operation not permitted
Assertion: 28595:1: Operation not permitted src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp 267
exception in initAndListen: 28595 1: Operation not permitted, terminating
shutdown: going to close listening sockets...
removing socket file: /tmp/mongodb-27017.sock
shutdown: going to flush diaglog...
now exiting
shutting down with code:100

now when I remove the volume mongo works but I need to persist my data so I need to mount the volume somehow, just not sure what i am doing wrong at this point.

I do see the files appearing in my folder but not sure why I get the 100 error

Answer 1

To get around this, you can employ a tool like rsync to move the db files into mapped directory while Mongo is running. The underlying bug has to do with latency between the Windows mapped volume and that bind path within the container. Offloading the work to rsync decouples the latency from Mongo's runtime requirements.

Example

Create a basic Dockerfile like this:

FROM mongo:latest

RUN apt-get update && \ 
    apt-get install -y \
        rsync

ADD init.sh /init.sh

Where init.sh is:

#!/bin/bash

migrate_db() {
  while true
  do
    rsync -avh /data/db/* /data/mapped-db
    sleep 5
  done
}

migrate_db &

#Execute a command
mongod --smallfiles --logpath=/dev/null --verbose &

#Wait
wait $!

Then, when launching the container, just start with ./init.sh as your ENTRYPOINT.