Purpose

MongoDB GridFS comes with some natural advantages such as scalability(sharding) and HA(replica set). But as it stores file in ASCII string chunks, there's no doubt a performance loss.

I'm trying 3 different deployments (different MongoDB drivers) to read from GridFS. And compare the results to classic Nginx configuration.

Contributors

Fan Fei ([email protected])

Neil Chen ([email protected])

Configurations

1, Nginx

location /files/ {
  alias /home/ubuntu/;
} 

open_file_cache kept off during the test.

2, Nginx_GridFS

It's a Nginx plugin based on MongoDB C driver. https://github.com/mdirolf/nginx-gridfs

Compile code & install

I made a quick install script in this repo, run it with sudo. After Nginx is ready, modify the configration file under /usr/local/nginx/conf/nginx.conf (if you didn't change the path).

Configuration

location /gridfs/{
   gridfs test1 type=string field=filename;
}

Use /usr/local/nginx/sbin/nginx to start Nginx. And use parameter -s reload if you changed the configuration file again.

3, Python

library version

• Flask 0.10.1
• Gevent 1.0.0
• Gunicorn 0.18.0
• pymongo 2.6.3

run application

cd flaskapp/
sudo chmod +x runflask.sh
bash runflask.sh

Script runflask.sh will start gunicorn with gevnet woker mode. Gunicorn configuration file here

4, Node.js

library version

• Node.js 0.10.4
• Express 3.4.7
• mongodb(driver) 1.3.23

run application

cd nodejsapp/
sudo chmod +x runnodejs.sh
bash runnodejs.sh

Test

Test items:

1. file served by Nginx directly
2. file served by Nginx_gridFS + GridFS
3. file served by Flask + pymongo + gevent + GridFS
4. file served by Node.js + GridFS

Files for downloading:

Run script insert_file_gridfs.py from MongoDB server to insert 4 different size of file to database test1(pymongo is required)

• 1KB
• 100KB
• 1MB

Test Environment

2 servers:

• MongoDB+Application/Nginx
• tester(Apache ab/JMeter)

hardware:

• Amazon EC2 m1.medium
• Ubuntu 12.04 x64

Concurrency

100 concurrent requests, total 500 requests.

ab -c 100 -n 500 ...

Result

Throughput

Time per request (download)

File size	Nginx+Hard drive	Nginx+GridFS plugin	Python(pymongo+gevent)	Node.js
1KB	0.174	1.124	1.982	1.679
100KB	1.014	1.572	3.103	3.708
1MB	9.582	9.567	15.973	18.317

You can get Apache ab report in folder: testresult

Server load

The server load is be monitored by command: vmstat 2

Nginx:

Nginx_gridfs

gevent+pymongo

Node.js

Conclusion

• Files served by Nginx directly

• No doubt it's the most efficient one, whether performance or server load.

• Support cache. In real world, the directive open_file_cache should be configured well for better performance.

• And must mention, it's the only one support pause and resume during the download(HTTP range support).

• For the rest 3 test items, files are stored in MongoDB, but served by different drivers.

• serve static files by application is really not an appropriate choice. They drains CPU too much and the performance is not good.
• nginx_gridfs (MongoDB C driver): downloading requests will be processed at Nginx level, which is in front of web applications in most deployments. Web application can focus on processing dynamic contents instead of static content.
• nginx_gridfs got the best performance comparing to other applications written in script languages. - The performance differences between Nginx and nginx_gridfs getting small after file size increased. But you can not turn a blind eye on the server load.
• pymongo and node.js driver: it's a draw game. Static files should be avoid to be served in productive applications.

Advantages of GridFS

• Put files in database make static content management much easier. We can omit maintain the consistency between files and its meta data in database.
• Scalable and HA advantages come with MongoDB

Drawbacks of GridFS

• bad performance
• can not resume downloading after pause or break

When should I use MongoDB GridFS

There are rare use cases I can imagine, especially in a performance sensitive system. But I may taste it in some prototype projects.

Here goes the answer from MongoDB official website, hope this will help. http://docs.mongodb.org/manual/faq/developers/#faq-developers-when-to-use-gridfs