How to connect using multiple nodes

[ghost]

Hi, thank you for this awesome project!

I am having trouble trying to connect to a Mongo 3.2.1 database which uses this string, provided by Compose.io:

mongodb://<user>:<password>@<host1>:<port1>,<host2>:<port2>/<db-name>?ssl=true

I tried using MONGO_URI in the configuration dictionary but it tries to connect to a local server:

/vagrant/env/local/lib/python2.7/site-packages/pymongo/topology.pyc in select_servers(self, selector, server_selection_timeout, address)
    116                 if server_timeout == 0 or now > end_time:
    117                     raise ServerSelectionTimeoutError(
--> 118                         self._error_message(selector))
    119 
    120                 self._ensure_opened()

ServerSelectionTimeoutError: localhost:27017: [Errno 111] Connection refused

Not sure how can I set my connection string, currently I am using just one node using these variables:

MONGO_HOST
MONGO_PORT
MONGO_DBNAME
MONGO_USERNAME
MONGO_PASSWORD

But I need to be able to use both to handle failover between nodes.

Any idea?

[nicolaiarocci]

The connection string is simply passed to pymongo. Could you try the pymongo uri parser and see if your string is parsed correctly?

[ghost]

Hi, it seems is parsed correctly (replaced actual values):

{'collection': None,
'database': 'something',
'nodelist': [('host1', 10520),
('host2', 10208)],
'options': {'ssl': True},
'password': 'secret',
'username': 'user'}

What can I do?

[nicolaiarocci]

Could you could try setting up a little python script which uses pymongo and your uri, bypassing Eve?

[ghost]

Good idea, I wrote this script and it worked (I needed ssl_ca_certs to make it work):

import ssl
from pymongo import MongoClient

uri = 'mongodb://user:password@host1:port1,host2:port2/database?ssl=true&ssl_ca_certs=cert.pem'
client = MongoClient(uri)
db = client['database']
collection = db['collection']
for c in collection.find():
    print c

I tried to use the same connection string in Eve using MONGO_URI option but it failed again, trying to connect to localhost instead of remote MongoDB.
ServerSelectionTimeoutError: localhost:27017: [Errno 111] Connection refused

How can I pass these options to Eve?

[nicolaiarocci]

Eve relies on Flask-PyMongo. Now, according to this ticket FPM does not support ssl and/or cert ca as parameters. I suspect that's the issue with your connection string.

You might want do the same experiment with Flask-PyMongo instead of barebone PyMongo, and see if it works on your setup. If the issue is with FPM, we will have to wait until it is fixed upstream.

[ghost]

I did this test and it worked:

from flask import Flask
from flask.ext.pymongo import PyMongo
app = Flask(__name__)
app.config["MONGO_URI"] = "mongodb://user:password@host1:port1,host2:port2/database?ssl=true&ssl_ca_certs=cert.pem"
mongo = PyMongo(app)

with app.app_context():
    for c in mongo.db.collection.find():
        print c

So it seems Flask-PyMongo actually supports this kind of connections.

[ghost]

Any idea on how can we fix this on Eve? Thanks!

[nicolaiarocci]

Hi, I just merged #990 with a fix for MONGO_URI. Maybe it helps with your issue?

[ghost]

Hi, I need to test again, as I am currently using an older version of Eve.

[tyomo4ka]

@nicolaiarocci @gustavo-gomez

It seems the problem is in Flask-PyMongo. I tried the following:

1. Create a cluster using Mongo Atlas.
2. Put the URI provided by Atlas into Eve configuration MONGO_URI field – it doesn't work.
3. Create a separate Python script with Flask-PyMongo – it doesn't work as well.
4. Create a separate Python script with just pymongo – it connects and shows my documents.

I played a little with Flask-PyMongo and it seems they parse MONGO_URI and then assemble it again instead of just bypassing to pymongo. Don't know why. Doesn't seem to me like a good idea.

[tyomo4ka]

@nicolaiarocci

The Flask-PyMongo seems to be abandoned. 0 contributions in 2017.

[nicolaiarocci]

Flask-PyMongo dependency was just dropped on branch v0.8.

[carlwgeorge]

FYI, the v0.8 tag still requires flask-pymongo in setup.py.

[nicolaiarocci]

Yes, good catch. It is fixed in v0.8.1.