[tor-dev] Searchable Tor descriptor and Metrics data archive - GSoC 2013

[Praveen Kumar]

Hi Karsten,

I am so sorry for replying late. I had a seminar presentation on Friday and
have another
on Monday, so I was a little busy studying for it.

I had downloaded about 1GB data of Server Descriptors from the metrics
website. I thought
of generating some performance metrics of a search application with a MySQL
backend and
with a MongoDB database backend in Django. So, I implemented two basic apps
with a MySQL
and MongoDB backend in Django. I processed each file and extracted
router_nickname, router_ip,
tor_version and platform_os as searchable fields for each server descriptor
file. At the time of writing this email, I had processed around 330,000
files for MySQL and have the data of 670,000 files in MongoDB. I can not
process all the files as that 1GB data is composed of millions of files and
processing is slow on my system.
My aim is to issue same queries to both the apps and see which one performs
better. Both the databases are
indexed on the same fields. I will tell you the metrics day after tomorrow
i.e on Tuesday.

But, theoretically speaking, MongoDB is fast because every document is
stored in JSON, it is schema less and doesn't has to preform any joins etc.
The indexes that are built are based on BTrees which have the worst case
time complexity of O(log(n)) for insertion, lookup and deletion. MongoDB
also keeps the indexes in RAM as required, for faster searches and to
reduce disk reads. MongoDB also has the capability of scaling efficiently.

I am now, somewhat, in favor of Django Haystack with Solr as the search
engine. Using MongoDB will
require us to spend considerable time developing the search interface which
will be responsible for handling complicated queries and then create
appropriate indices to handle those complicated queries.



On Thu, Apr 11, 2013 at 1:50 PM, Karsten Loesing <karsten at torproject.org>wrote:

> On 4/10/13 11:44 PM, Praveen Kumar wrote:
> > I am Praveen Kumar from India. I want to work on the project "Searchable
> > Tor descriptor and Metrics data archive". I have participated in the past
> > instances of GSoC with Melange and e-cidadania, and have an extensive
> > experience in development with Python.
> >
> > For the search application, I propose using Django with MongoDB as a
> NoSQL
> > database backend for our search application. We have 100GB+ of data which
> > eventually grows everyday and so using a NoSQL backend will ensure us
> that
> > our application scales well with the increase in data as well as user
> > traffic.
> >  The application will have various interfaces such as:
> > 1) Data Updator: This end will connect and retrieve data from the metrics
> > website periodically via rsync. It will also be responsible for
> > pre-processing the data to a suitable format as our search application
> > needs.
> > 2) Storage End: A relay descriptor can be searched by nickname,
> > fingerprint, IP Addr and various other attributes that define a relay
> > descriptor. So we can preprocess the whole data, extract the attributes
> > that define a descriptor and then save it in an appropriate model MongoDB
> > provides. Since queries are very fast in a NoSQL datastore, our searches
> > will be very fast.
> > 3) Search Front End: This will be exposed to the user where a user
> provides
> > its search query to us.
> > 4) Search query processor: This end will process the query of a user and
> > determine its type for eg. whether the query is an IP Address or a
> nickname
> > etc. It will then connect with our Storage End and return the appropriate
> > data to the Search Front End.
> >
> > Above is a very high level view of my approach to this project. We can
> also
> > use Django Haystack as a search application framework(I did some research
> > for existing search frameworks). I can implement this app in an object
> > oriented way in Python. Python being such a beautiful and easy to
> > understand language, it will be easy for others to understand and make
> > changes to the application in least amount of time.
> >
> > I would like to know if I am thinking in the right direction and would
> like
> > to know what Karsten has to say about this.
>
> Hi Praveen!
>
> Glad to see that you're interested in this project!
>
> Your high-level description makes sense to me.  I guess the point where
> I'd expect more details in a GSoC application is where you say: "Since
> queries are very fast in a NoSQL datastore, our searches will be very
> fast."
>
> See also the last paragraph in the project idea: "Applications for this
> project should come with a design of the proposed search application,
> ideally with a proof-of-concept based on a subset of the available data
> to show that it will be able to handle the 100G+ of data."  I'd like to
> understand why you think MongoDB will handle searches sufficiently fast.
>
> As an alternative to relying on NoSQL databases doing magic is to
> investigate Django Haystack and other existing search application
> frameworks.
>
> Note that I don't know what's the best tool or design here.  But I ran
> into too many pitfalls in the past when I thought a database design was
> fast enough to provide data for an Internet-facing service.  That's why
> I'd like to see a convincing design first, bonus points if it comes with
> a proof of concept.
>
> Best,
> Karsten
>
>


-- 
Cheers

Praveen
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