Copying mongo db using pymongo tutorial example fails: "OperationFailure: no such command: 'copydb'"

Question

I'm trying to copy my db for testing purposes. I'm using the docs for that, but it still fails:

from pymongo import MongoClient

client = MongoClient(username='root', password='pass')
client.admin.command('copydb', fromdb='src', todb='dst')


OperationFailure: no such command: 'copydb', full error: {'ok': 0.0, 'errmsg': "no such command: 'copydb'", 'code': 59, 'codeName': 'CommandNotFound'}

When trying another command, from another section of the doc, it worked:

from pymongo import MongoClient

client = MongoClient(username='root', password='pass')
db = client.src
db.admin.command('copydb', fromdb='src', todb='dst')

The objects used here are different, but this is what the docs say... I still tried using the db object for the copydb - and failed again:

from pymongo import MongoClient

client = MongoClient(username='root', password='pass')
db = client.src
db.admin.command('buildinfo')

TypeError: 'Collection' object is not callable. If you meant to call the 'command' method on a 'Collection' object it is failing because no such method exists.

which means I use a bad object (makes sense, but I don't get how to make it work)

pymongo.version: '3.11.0'
mongodb version: 4.4.1 (running on docker)

Starting in version 4.2, MongoDB removes the copydb command. The deprecated db.copyDatabase(), which wraps the copydb command, can only be run against MongoDB 4.0 or earlier versions. https://docs.mongodb.com/manual/reference/method/db.copyDatabase/ — Anurag Wagh, Oct 21 '20 at 11:57
@AnuragWagh Saw it now. I'm downgrading and checking (Works!), but surely there is a replacement method for newer versions, no? — CIsForCookies, Oct 21 '20 at 11:58
An alternative would be to use `mongodump` and `mongorestore` commands https://docs.mongodb.com/database-tools/mongodump/#copy-clone-a-database But `pymongo` doesn't have an API which can `dump` and `restore` — Anurag Wagh, Oct 21 '20 at 12:01
On the other hand, you can try `os`, `shutil` or `subprocess` to execute these shell commands https://stackoverflow.com/questions/89228/how-to-call-an-external-command — Anurag Wagh, Oct 21 '20 at 12:02
@AnuragWagh I'm not sure this is possible... My host has no `mongod`, only `pymongo`. How could I access the `mongodump` from the host? — CIsForCookies, Oct 21 '20 at 12:10

score 0 · Answer 1 · answered Oct 21 '20 at 12:52

Using the help from @AnuragWagh and this nice answer I managed to have my own script to handle dump & restore:

from bson.json_util import dumps, loads
import os
import pymongo


def backup_db(client, db_name, backup_dir):
    if not os.path.isdir(backup_dir):
        os.makedirs(backup_dir)

    database = client[db_name]
    collections = database.list_collection_names()

    for i, collection_name in enumerate(collections):
        col = getattr(database,collections[i])
        collection = col.find()
        jsonpath = collection_name + '.json'

        jsonpath = os.path.join(backup_dir, jsonpath)

        with open(jsonpath, 'wb') as jsonfile:
            jsonfile.write(dumps(collection).encode())


backup_dir = './bckp'
client = pymongo.MongoClient(host='localhost', username='root', password='pass')
src_db_name = 'Jenkins'
dst_db_name = 'Test'
backup_db(client, src_db_name, backup_dir)


for backup_collection in filter(lambda path: path.endswith('.json'), os.listdir(backup_dir)):
    collection_name = backup_collection.rstrip('.json')
    with open(os.path.join(backup_dir, backup_collection), 'rb') as backup_file:
        data = loads(backup_file.read())
        client[dst_db_name][collection_name].insert_many(data)

This is not the ideal solution. If you can, use mongodump & mongorestore. For my case (pymongo on a host without mongodb installed, this seems like the best solution)

Copying mongo db using pymongo tutorial example fails: "OperationFailure: no such command: 'copydb'"

1 Answers1