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Python+Mongo+Django framework for creating simple, pluggable analytics based on streaming events.

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README.md

edX Insights

This is a development version of an analytics framework for the edX infrastructure. It will replace the ad-hoc analytics used in the software previously. The goal of this framework is to define an architecture for simple, pluggable analytics modules. The architecture must have the following properties:

  1. Easy to use. Professors, graduate students, etc. should be able to write plug-ins quickly and easily. These should be able to run in the system without impacting the overall stability. Results should be automatically shown to customers.
  2. The API must support robust, scalable implementations. The current back-end is not designed for mass scaling, but the API for the modules should permit e.g. sharding in the future.
  3. Reusable. The individual analytics modules should be able to use the results from other modules, and people should be able to build on each others' work.
  4. Interoperable. We would like the framework to be sufficiently generic to be useable outside of edX.
  5. Cross-scope. There should be a smooth path from off-line analytics, to on-line batched analytics (e.g. for an instructor dashboard), to on-line realtime analytics (e.g. for the system to react to an event the analytics detects).

The model behind Insights is the app store model: App store As with an app store (Android shown above), we provide a runtime. This runtime provides a fixed set of technologies (Python, numpy, scipy, pylab, pandas, mongo, a cache, etc.). If you restrict yourself to this runtime, anyone running Insights can host your analytic. If you'd like to move outside this set of tools, you can do that too, but then you may have to host your own analytics server.

Comparison to other systems:

  • Tincan is an SOA and a format for streaming analytics. Insights is an API and runtime for handling those events. The two are very complementary.
  • Twitter Storm is a framework for sending events around. Insights is an API and runtime which would benefit from moving to something like storm.
  • Hadoop is a distributed computation engine. For most learning analytics, hadoop is overkill, but it could be embedded in an analytics module if desired.

Examples

Views show up in the dashboards. To define an analytic which just shows "Hello World" in the analytics dashboard:

@view()
def hello_world():
   return "<html>Hello world!</html>"

Queries return data for use in other parts of the system. If you would like to define a new analytic which shows a histogram of grades, the first step would be to define a query while will return grades. How this is done depends on your LMS, but it is often convenient to define a dummy one which does not rely on having a functioning LMS present. This is convenient for off-line development without live student data:

@query()
def get_grades(course):
    ''' Dummy data module. Returns grades  
    '''
    grades = 3*numpy.random.randn(1000,4)+ \
        12*numpy.random.binomial(1,0.3,(1000,4))+40
    return grades

Once this is in place, you can define a view which will call this query:

@view()
def plot_grades(fs, query, course):
    grades = query.get_grades(course)
    filename = course+"_"+str(time.time())+".png"
    title("Histogram of course grades")
    hist(grades)
    f = fs.open(filename, "w")
    savefig(f)
    f.close()
    fs.expire(filename, 5*60)
    return "<img src="+fs.get_url(filename)+">"

At this point, the following will show up in the instructor dashboard:

Grade histogram

Note that the query and the view don't have to live on the same machine. If someone wants to reuse your grade histogram in a different LMS, all they need to do is define a new get_grades query.

To build a module which takes all in coming events and dumps them into a database:

@event_handler()
def dump_to_db(mongodb, events):
    collection = mongodb['event_log']
    collection.insert([e.event for e in events])

Except for imports, that's all that's required.

Architecture

A block diagram of where the analytics might fit into an overall learning system is:

System structure

The learning management system (and potentially other sources) stream events to the analytics framework. In addition, the modules in the framework will typically have access to read replicas of production databases. In practice, a lot of analytics can be performed directly from the LMS databases with a lot less effort than processing events.

A single module

A rough diagram of a single analytics module is:

Analytics module

Each module in the analytics framework is an independent Python module. It has its own Mongo database, a filesystem abstraction, as well as a cache. In addition, it can have access to read-replicas of production databases, and in the near future, it will have access to read replicas of other module's databases.

Note that all of these are optional. A hello world module could be as simple as defining a single view:

@view()
def hello_world():
   return "<html>Hello world!</html>"

If you wanted the view to be per-user, you could include a user parameter:

@view()
def hello_world(user):
   return "<html>Hello "+user+"</html>"

The views and queries are automatically inspect for parameters, and the system will do the right thing. If you would like to have a per-module database, simply take a db parameter. Etc.

To understand how to build modules in more detail, the best place to start is by reading the module which defines testcases -- the file modules/testmodule/init.py. Next place is to look at the code for the decorators. Final place is for the main views and dashboard.

Using with other LMSes

The architecture is designed to be usable with common analytics shared between multiple LMSes. The structure for this is:

Multipule LMSes

Here, each instance has a data layer module. This module translates the data generate by the particular LMS into a common representation. Higher-level analytics are built on top of that common representation. We're trying to come up with process for creating this data layer, but it's not essential we get it 100% right. In most cases, it is relatively easy to include backwards-compatibility queries.

Structuring servers

The system is transparent to how analytics are split across servers. There are several models for how this might be used.

First, we might have a production-grade code on e.g. a critical server which keeps student profile/grading/etc. information, while still maintaining prototype analytics servers, which may be on-line more intermittently:

Multiple servers

A second way to use this might be by function. For example, we might embed analytics in the LMS, in the forums, in the wiki, in the student registration system, and in other parts of the system. Those would provide access to data from those subsystems. We may also wish to have specialized runtimes providing access to additional tools like Hadoop or R. A single computer can query across all of these servers from the Insights API:

Per-system analytic

Installing

Follow the instructions in INSTALL.md

If installed for development, the advertised views and queries for the test module will be at:

http://127.0.0.1:8000/static/index.html

Running periodic tasks

Periodic tasks (which are scheduled with core.decorators.cron) rely on Celery for execution. It is the reponsability of the client django project to ensure Celery is configured and running. To configure, add the following to settings.py of your django project:

from edinsights.celerysettings import * 

To start celery, run from your django project

python manage.py celery worker -B

Only tasks located in files named "tasks.py" located in the main directory of your django project or installed django app will be scheduled.

Building on top of the framework

To build on top of the framework, you will need several things:

  • A log handler which can stream the events out over an SOA. The ones we wrote for edX are available at: https://github.com/edx/loghandlersplus
  • A way of piping these events into the analytics framework. The version we wrote for edX is available at: https://github.com/edx/djeventstream On a high level, this is a module which sends Django signals of type djeventstream.signals.event_received. The events are JSON dictionaries. The event handler can handle either dictionaries, lists of dictionaries, or JSON-encoded string representations of both.
  • A way of embedding the analytics in your LMS based on the SOA.
  • Potentially, some set of analytics modules. At the very least, you should define appropriate (TBD) properties to ornament your events with and appropriate queries (TBD) to get data out of your read-replica databases, so that modules written by other folks can get at your data in a generic way. The best way to understand how to do this is to read test cases in modules/testmodule/init.py

A very minimal example of how to build applications on top of this framework is in the example directory.

Using Analytics Externally (djobject)

djobject.py has an abstraction for accessing analytics both locally (function calls) and remotely (RPC). This is a standard Python object. All of the standard Python introspection of the methods in this object works.

This is, in particular, useful for off-line analytics. You have access to the raw data, analyzed data, and queries defined by other analytics modules. For example, given a time_on_task module, you could call event.time_on_task to get the time between that event and the following event. Or you could call query.irt(problem) to get the IRT parameters for that problem.

When using analytics remotely, there are issues of security and permissions. Specifically, a sysadmin might want to see an analytic per-course/per-student. An instructor of that course might want to have that fixed to the course (so it transforms into a per-student analytic). djobject's transform_embed defines a DSL for restricting permissions to analytics, as well as for fixing specific commandline parameters. This DSL should be cleaned up, but it's good enough for now.

Multiple analytics servers can be merged into one djobject.

There is an issue of network reliability and timeouts when access remotely. You can set timeouts on djembed objects to manage those issues.

Shortcuts/invariants

  • Template rendering is a hack.
  • Duplicate events/downtime is not handled.
  • At present, events come into the system through an SOA. The tracking framework is modified to use a Python HTTP logger, which are received by the framework. For most events, this should be replaced with something asynchronous, as well as queued, such as Twitter storm.
  • The analytics have limited isolation from each other. They can run on seperate servers, but with multiple modules on one server, there is no isolation. The architecture supports running each module in its own sandbox. This should not be broken (e.g. by having direct calls across modules).
  • Right now, all functions must be process-safe (the function gets called multiple times, although in different memory spaces). Some folks would like to write an analytic that runs in a single process without worrying about thread safety (e.g. while(true) { get_event(); handle_event(); }). The API is designed to support this, but this is not implemented.
  • The analytics framework has no way to generate new events. This would be useful for chaining analytics. This is trivial to add.
  • There are no filters. E.g. an event handler cannot ask for all video events. This is high priority. This is trivial to add.

Desired Modes of operation

  1. Hard realtime. When an event comes in, it is synchronously processed. The caller knows that by the time the event returns, it can extract results from the analytic.
  2. Soft realtime. There is a queue, but processing is fast enough that the queue is assumed to be nearly empty.
  3. Queued. There is a queue with potentially a significant backlog.
  4. Batched. Processing runs at e.g. 5 minute or 1 day intervals.
  5. Off-line. There is a database populated with data, and the data is analyzed by hand.

For developing the system, hard realtime is the most critical, and we'd like to keep the invariant that it works. Next most useful is either queued or batched.

Sharding

Some types of analytics support sharding per-resource (e.g. number of views) or per-student (e.g. time spent in course). Some require global optimization and cannot be sharede (e.g. IRT). This is something we'll need to eventually think about, but this is a 2.0 feature. Note that the current decorator design pattern does not help -- it merely helps define a storage API. A statistic like class rank may be per-user, but require data from all users.

Useful pointers

Pivotal Tracker has a set of possible metrics of mixed quality. The wiki has another set of possible metrics. The most useful metrics we've found were in competing systems and in publications from the research community.

Gotchas

  • For events to flow in, a decorator in core.views must be called. This must be iported from the main appliction.
  • Sometimes, the network transparency isn't quite right. This is a bug.
  • Are there still any Python path issues if you have this installed and are developing from source?

Product Backlog

  1. Add support for asynchronous views. When the client issues a request for a view which takes a while to calculate, there should be visual feedback.
  2. Move views into an iframe.
  3. Create appropriate userspace. We need higher-level functions to extract information from events.
  4. Find ways to handle and drop duplicate events.
  5. Find ways to handle robust, queued events
  6. The API for genetic event properties (e.g. event.actor) should support namespaces (e.g. event.tincan.actor) and generic dispatch (e.g. one module defines event.tincan.actor for events from Sakai, and another for events from edX, and the right one gets called). Note that, in the short term, no namespace is required (for being able to access data), while namespaces is only important (for clean abstractions).
  7. Better error handling and escalation.
  8. Better off-line support.
  9. Extend the property API to support not just events. We'd like to have things like problem.difficulty (from IRT), or video.rewinds, etc.
  10. Make the types of parameters passed (user, resource, etc.) static, rather than dynamic.
  11. Better batch processing. We add a module. It should be able to get all past events.

Other useful next steps

  1. Test infrastructure. We should have a dummy dataset and database, and be able to confirm output of all queries.
  2. Development data. We need sample outputs for all queries for when the DB is not available for UI development (some of this exists).

Needs of edX

edX currently has many sources of data:

  1. User tracking events. The software has a middleware layer which captures all data (within reason) that the user sends to the server. In addition, the server is instrumented, where necessary, to capture context for this (e.g. for a problem submission, we also need to capture the random number seed used to generate that problem). The JavaScript is instrumented to capture most of what the user does client-side (e.g. textbook page turns or video scrubs). These events are captured in a Python logger, and streamed into this framework. The structure of these events is (intentionally) quite simple and general. We are ontology-agnostic.
  2. Databases. The application-layer of the analytics framework has or will have access to databases through read replicas.
  3. External services used for surveys and mailings. This is not currently integrated.
  4. Course data. Most of this is in the read replica databases, but for some courses, this lives in github repositories of XML files. This is not currently integrated.
  5. Course-specific services (e.g. CS50 forums, Berkeley graders, etc.)
  6. E-mails to course staff.
  7. Anecdotal interactions.

We need to be able to aggregate these into useful information for students, instructors, researchers, marketers, etc.

Architecture Expansions

We would like to also support FERPA-compliance. This could be built in one of two ways. Per-school stacks, including analytics:

Split analytics:

The API supports either. Building out back-end support for either would be substantial work.

Other edX Code

This code was developed as part of edX. See code.edx.org for other code from edX.

License

The code in this repository is licensed under version 3 of the AGPL unless otherwise noted.

Please see LICENSE.txt for details.

How to Contribute

Contributions are very welcome. The easiest way is to fork this repo, and then make a pull request from your fork. The first time you make a pull request, you may be asked to sign a Contributor Agreement.

Reporting Security Issues

Please do not report security issues in public. Please email security@edx.org

Mailing List and IRC Channel

You can discuss development specific to this package, as well as general learning analytics and educational datamining on the insights-dev Google Group. General edX platform discussion can happen on the edx-code Google Group or in the edx-code IRC channel on Freenode.

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