sofine 0.1.3

What Problem Does sofine solve?

You need to get data related to a set of keys from many sources: web scrapers, Web APIs, flat files, data stores. Wouldn’t it be nice to build one combine data set over multiple calls with one command line, REST or Python call? Wouldn’t it be great if each data retrieval script you wrote was a reusable plugin that you could combine with any other?

You need a “glue API.”

This is the problem sofine solves. It’s a small enough problem that you could solve it yourself. But sofine is minimal to deploy and write plugins for, and has already solved in an optimally flexible way the design decisions you would have to solve.

Features

1. Do (almost) no more work than if you wrote a one-off data collection scripts

2. Manage your plugins in any directory with any directory structure you like

3. Call plugins from the command line, as REST resources or from Python

4. Chain as many plugin calls as you want together and get back one JSON data set with all the data collected from all the chained calls

5. If called from the command line, sofine reads data from stdin if it is present, and always outputs to stdout. So sofine piped calls, such as the example above, can themselves be composed in larger piped expressions.

For fun, here is an example of features 4 and 5, combining a sofine pipeline with the fantastic JSON query tool jq for further filtering.

echo '{"AAPL":{}}' | python $PYTHONPATH/sofine/runner.py '--SF-s ystockquotelib --SF-g example | --SF-s google_search_results --SF-g example' | jq 'map(recurse(.results) | {titleNoFormatting}'

Overview

To get started, you install the library, create a plugin directory, assign the plugin directory to an environment variable, and start writing plugins. Plugins require two attributes and one method in the simple case and three methods in the most elaborate edge case. You can optionally define two additional attributes for clients to use to introspect your plugin.

sofine ships with a few useful plugins to get you started and give you the idea; you can combine these with your custom plugins with no additional configuration or code. The included plugins are:

• sofine.plugins.standard.file_source - Retrieves keys from a JSON file to add to the data set being built. See here for the details.

• example.archive_dot_org_search_results - Takes a search query and returns results from www.archive.org

• example.google_search_results - Takes a search query and returns results from the Google Search API

• example.fidelity - Takes a userId, pin, accountId and email, logs into Fidelity, scrapes the account portfolio and returns the tickers found as keys and four attributes of data for each ticker

• example.ystockquotelib - Takes a list of tickers and returns the data available from Yahoo! Finance for each ticker

Here is what usage looks like …

From the command line:

$ echo '{"AAPL":{}}' | python $PYTHONPATH/sofine/runner.py '--SF-s ystockquotelib --SF-g example | --SF-s google_search_results --SF-g example'

REST-fully:

$ python $PYTHONPATH/sofine/rest_runner.py

$ curl -X POST -d '{"AAPL":{}}' --header "Content-Type:application/json" http://localhost:10000/SF-s/ystockquotelib/SF-g/example/SF-s/google_search_results/SF-g/example

From Python:

import sofine.runner as runner

data = {"AAPL": {}}
data_sources = ['ystockquotelib', 'google_search_results']
data_source_groups = ['example', 'example']
data_source_args = [[], []]
data = runner.get_data_batch(data, data_sources, data_source_groups, data_source_args)

All three calling styles return the same data set. sofine data sets map JSON objects of data to string keys. So here, we have the key “AAPL,” with all the attributes retrieved from Yahoo! Finance and the Google Search API combined in a JSON object associated with the key. Notice that the keys in the attribute data set are namespaced so multiple calls can’t overwrite data from each other.

{
"AAPL": {
    "example::google_search_results::results": [
        {
            "GsearchResultClass": "GwebSearch",
            "cacheUrl": "http://www.google.com/search?q=cache:XhbIlCyrcXMJ:finance.yahoo.com",
            "content": "View the basic <b>AAPL</b> stock chart on Yahoo! Finance. Change the date range, chart type and compare Apple Inc. against other companies.",
            "title": "<b>AAPL</b>: Summary for Apple Inc.- Yahoo! Finance",
            "titleNoFormatting": "AAPL: Summary for Apple Inc.- Yahoo! Finance",
            "unescapedUrl": "http://finance.yahoo.com/q?s=AAPL",
            "url": "http://finance.yahoo.com/q%3Fs%3DAAPL",
            "visibleUrl": "finance.yahoo.com"
        },
        ...
        ...
    ],
    "example::ystockquotelib::avg_daily_volume": "59390100",
    "example::ystockquotelib::book_value": "20.193",
    "example::ystockquotelib::change": "+1.349",
    "example::ystockquotelib::dividend_per_share": "1.7771",
    "example::ystockquotelib::dividend_yield": "1.82",
    "example::ystockquotelib::earnings_per_share": "6.20",
    "example::ystockquotelib::ebitda": "59.128B",
    "example::ystockquotelib::fifty_day_moving_avg": "93.8151",
    "example::ystockquotelib::fifty_two_week_high": "99.24",
    "example::ystockquotelib::fifty_two_week_low": "63.8886",
    "example::ystockquotelib::market_cap": "592.9B",
    "example::ystockquotelib::price": "99.02",
    "example::ystockquotelib::price_book_ratio": "4.84",
    "example::ystockquotelib::price_earnings_growth_ratio": "1.26",
    "example::ystockquotelib::price_earnings_ratio": "15.75",
    "example::ystockquotelib::price_sales_ratio": "3.28",
    "example::ystockquotelib::short_ratio": "1.70",
    "example::ystockquotelib::stock_exchange": "\"NasdaqNM\"",
    "example::ystockquotelib::two_hundred_day_moving_avg": "82.8458",
    "example::ystockquotelib::volume": "55317688"
}
}

Installing sofine

pip install sofine

Then, make sure your $PYTHONPATH variable is set and points to the site-packages directory of your Python where pip installed sofine.

export PYTHONPATH=<MY PYTHON SITE-PACKAGES DIRECTORY>

Then, create a plugin directory and assign its path to an environment variable SOFINE_PLUGIN_PATH. You probably want to add it to your shell configuration file.

export SOFINE_PLUGIN_PATH=<MY PATH>

sofine runs its REST server on port 10000. If you want to use a different port, set the environment variable SOFINE_REST_PORT. You probably want to add it to your shell configuration file.

export SOFINE_REST_PORT=<MY PORT>

If you want to use the included fidelity and ystockquotelib plugins in the plugins.examples plugin group, also install the following:

easy_install mechanize
easy_install beautifulsoup4
pip install ystockquote

How Plugins Work and How to Write Them

All plugins inherit from a base class which defines four attributes:

• self.name - string. The name of the plugin

• self.group - string. The pluging group of the plugin. This the subdirectory in the plugin directory into which the plugin is deployed.

• self.schema - list of string. The set of attribute keys that calls to get_data can associate with a key passed to get_data.

• self.adds_keys - boolean. Indicates whether the plugin adds keys to the data set being built or only adds attributes to existing keys.

You must always define name and group. name must match the module name of the plugin module, that is the name you would use in an import statement. group must match the name of the subdirectory of your plugin directory where the plugin is deployed. sofine uses name and group to load and run your plugin, so they have to be there and they have to be correct.

schema and adds_keys are optional. They allow users of your plugin to introspect your plugin. schema is a list of strings that tells a client of your plugin the set of possible attribute keys that your plugin returns for each key it recieves. For example, if your plugin takes stock tickers as keys and looks up a current quote, its schema declaration might look like this:

self.schema = ['quote']

adds_keys lets users ask your plugin if it adds keys to the data set being built when sofine calls it, or if it just adds attributes for the keys it receives. For example, the ystockquotelib plugin in the sofine.plugins.example group takes a set of stock tikckers as keys and retrieves the available data for each of them from Yahoo! Finance. This plugin has the attribute declaration self.adds_keys = False. On the other hand, the sofine.plugins.fidelity plugin is a scraper that can log into the Fidelity, go to the portfolio page for the logged in user, scrape all the tickers for the securities in that portfolio, and add those keys and whatever data it finds to the data set being built. This plugin has a value of True for adds_keys.

NOTE: A common design pattern is to start a chain of calls with a plugin that adds keys, and then pass those keys to one or more plugins that don’t add keys but rather retrieve data for that set of keys.

Plugins also have three methods. get_data is not implemented in the base class and must be implemented by you in your plugin. This method takes a list of keys and a list of arguments. It must return a dict whose keys are a proper superset of the keys it received (the return set of keys can have more keys than were passed to get_data if the plugin adds keys). This dict must have string keys and a dict value for each key. The dict value is the data retrieved for each key. The keys in that dict must be a set of strings that is a proper subset of the set of strings in self.schema.

Here is an example of get_data from the sofine plugin sofine.plugins.example.ystockquotelib.

def get_data(self, keys, args):
    """
    * `keys` - `list`. The list of keys to process.
    * `args` - `'list`. Empty for this plugin.
    Calls the Yahoo API to get all available fields for each ticker provided as a key in `keys`."""
    return {ticker : ystockquote.get_all(ticker) for ticker in keys}

The other method you will often need to implement is parse_args. If your get_data requires no arguments you need not implement parse_args and can just use the base class default implementation. But if your get_data call requires arguments, you must implement parse_args. The method takes an argv style list of alternating arg names and values and is responsible for validating the correctness of argument names and values and returing a tuple with two members. The first member is a boolean is_valid. The second is the parsed list of argument values (without the argument names).

Here is an example from the sofine plugin sofine.plugins.standard.file_source.

def parse_args(self, argv):
    """`[-p|--path]` - Path to the file listing the keys to load into this data source."""

    usage = "[-p|--path] - Path to the file listing the keys to load into this data source."
    parser = OptionParser(usage=usage)
    parser.add_option("-p", "--path",
                    action="store", dest="path",
                    help="Path to the file listing the keys to load into this data source. Required.")
    (opts, args) = parser.parse_args(argv)

    is_valid = True
    if not opts.path:
        print "Invalid argument error."
        print "Your args: path {0}".format(opts.path)
        print usage
        is_valid = False

    return is_valid, [opts.path]

The third method is get_schema. You will rarely need to implement this. Any plugin that knows the set of attributes it can return for a key doesn’t need to implement get_schema and can rely on the default. Note that get_schema returns the set of attribute keys you define in self.schema in a namespace qualified with the plugin group and name. For example, if our stock quote plugin mentioned above is named get_quotes and it is in the trading group, the return value of get_schema would be ["trading::get_quotes::quote"].

Finally, the last line of your plugin should assign the module-scope variable plugin to the name of your plugin class. For example:

plugin = GoogleSearchResults

import urllib
import urllib2
import json

def query_google_search(k):
    url = 'http://ajax.googleapis.com/ajax/services/search/web?v=1.0&q={0}'.format(urllib.quote(k))
    ret = urllib2.urlopen(url)
    ret = ret.read()
    ret = json.loads(ret)

    if ret:
        ret = {'results' : ret['responseData']['results']}
    else:
        ret = {'results' : []}

    return ret

from sofine.plugins import plugin_base as plugin_base

class GoogleSearchResults(plugin_base.PluginBase):

    def __init__(self):
        self.name = 'google_search_results'
        self.group = 'example'
        self.schema = ['results']
        self.adds_keys = False

    def get_data(self, keys, args):
        return {k : query_google_search(k) for k in keys}

plugin = GoogleSearchResults

froe sofine.plugins import plugin_base as plugin_base
import ystockquote

class YStockQuoteLib(plugin_base.PluginBase):

    def __init__(self):
        self.name = 'ystockquotelib'
        self.group = 'example'
        self.schema = ['fifty_two_week_low', 'market_cap', 'price', 'short_ratio',
                       'volume','dividend_yield', 'avg_daily_volume', 'ebitda',
                       'change', 'dividend_per_share', 'stock_exchange',
                       'two_hundred_day_moving_avg', 'fifty_two_week_high',
                       'price_sales_ratio', 'price_earnings_growth_ratio',
                       'fifty_day_moving_avg', 'price_book_ratio', 'earnings_per_share',
                       'price_earnings_ratio', 'book_value']
        self.adds_keys = False

    def get_data(self, keys, args):
        return {ticker : ystockquote.get_all(ticker) for ticker in keys}

plugin = YStockQuoteLib

How to Call Plugins

As we saw above in the Introduction section, there are three ways to call plugins, from the command line, as REST resources, or in Python. When calling plugins to retrieve data, you need to pass three or four arguments, data, the plugin name, the plugin group and, depending on the call, the plugin action.

There are four actions, which correspond to the three methods get_data, parse_args and get_schema, while adds_keys returns the value of the the plugin’s self.adds_keys.

get_data
parse_args
get_schema
adds_keys

python $PYTHONPATH/sofine/runner.py '--SF-s fidelity --SF-g example -c <CUSTOMER_ID> -p <PIN> -a <ACCOUNT_ID> -e <EMAIL> | --SF-s ystockquotelib --SF-g example'

curl -X POST -d '{}' --header "Content-Type:application/json" http://localhost:10000/SF-s/fidelity/SF-g/example/c/<CUSTOMER_ID>/p/<PIN>/a/<ACCOUNT_ID>/e/<EMAIL>/SF-s/ystockquotelib/SF-g/example

import sofine.runner as runner

data = {}
data_sources = ['fidelity', 'ystockquotelib']
data_source_groups = ['example', 'example']
data_source_args = [[customer_id, pin, account_id, email], []]
data = runner.get_data_batch(data, data_sources, data_source_groups, data_source_args)

import sofine.runner as runner

data = {}
data_sources = ['fidelity', 'ystockquotelib']
data_source_groups = ['example', 'example']
data_source_args = [[customer_id, pin, account_id, email], []]
data = runner.get_data_batch(data, data_sources, data_source_groups, data_source_args)

python $PYTHONPATH/sofine/runner.py '--SF-s file_source --SF-g standard --SF-a parse_args -p "./sofine/tests/fixtures/file_source_test_data.txt"'

curl -X POST -d '{}' --header "Content-Type:application/json" http://localhost:10000/SF-s/file_source/SF-g/standard/SF-a/parse_args/p/.%2Fsofine%2Ftests%2Ffixtures%2Ffile_source_test_data.txt

def test_parse_args_file_source(self):
    data_source = 'file_source'
    data_source_group = 'standard'
    path = './sofine/tests/fixtures/file_source_test_data.txt'
    args = ['-p', path]
    actual = runner.parse_args(data_source, data_source_group, args)

    self.assertTrue(actual['is_valid'] and actual['parsed_args'] == [path])

python $PYTHONPATH/sofine/runner.py '--SF-s ystockquotelib --SF-g example --SF-a get_schema'

curl -X POST -d '{}' --header "Content-Type:application/json" http://localhost:10000/SF-s/ystockquotelib/SF-g/example/SF-a/get_schema

data_source = 'ystockquotelib'
data_source_group = 'example'
schema = runner.get_schema(data_source, data_source_group)

for name, group in plugin_map:
    prev_keys = set(data.keys())
    data = runner.get_data(data, name, group, args_map[name])

    if runner.adds_keys(name, group):
        new_keys = set(data.keys()) - prev_keys
        logger.log(new_keys)

python $PYTHONPATH/sofine/runner.py '--SF-s ystockquotelib --SF-g example --SF-a adds_keys'

curl -X POST -d '{}' --header "Content-Type:application/json" http://localhost:10000/SF-s/ystockquotelib/SF-g/example/SF-a/adds_keys

data_source = 'ystockquotelib'
data_source_group = 'example'
adds_keys = runner.adds_keys(data_source, data_source_group)

data_source = 'google_search_results'
data_source_group = 'example'
plugin = runner.get_plugin(data_source, data_source_group)
schema = plugin.schema

data_source = 'google_search_results'
data_source_group = 'example'
mod = runner.get_plugin_module(data_source, data_source_group)
# The google plugin implements an additional helper method in the module that returns
# the list of attributes in each 'results' object it returns mapped to each key
child_shema = mod.get_child_schema()

Managing Plugins

Managing plugins is very simple. Pick a directory from which you want to call your plugins. Define the environment variable SOFINE_PLUGIN_PATH and assign it to the path to your plugin directory.

Plugins themselves are just Python modules fulfilling the requirements detailed in the section, “How Plugins Work and How to Write Them.”

Plugins cannot be deployed at the root of your plugin directory. Instead you must create one or more subdirectories and place plugins in them. Any plugin can live in any subdirectory. If you want, you can even place a plugin in more than one plugin directory. The plugin module name must match the plugin’s self.name attribute, and the plugin directory name must match the plugin’s self.group attribute.

This approach means you can manage your plugin directory without any dependencies on sofine. You can manage your plugins directory like any other source code repo, and include unit tests for plugins anywhere in the plugin directory if you want.

Appendix: The Data Retrieval Algorithm

• The returned data set (let’s call it “data”) is always a JSON object of string keys mapped to object values.

• On every call in a sofine chain, add any new keys returned to data, and add all key attribute data returned to that key in data.

• All attributes mapped to a key are JSON objects which themselves consist of string keys mapped to legal JSON values.

• All attribute keys are namespaced with the prefix of the plugin group and plugin name and then the attribute key name, guaranteeing they are unique.

So, formally, the result of a call to a sofine pipe is the union of all keys retrieved by all plugin calls, with each key mapped to the union of all attributes returned by all plugin calls for that key.

Developing With the sofine Code Base

All of the above documentation covers the very common case of using sofine as a library to manage and call your own plugins.

However, you might want to develop with sofine more directly. Perhaps you want to use pieces of the library for other purposes, or fork the library to add features, or even contribute!

In that case, you’ll want the developer documentation: http://marksweiss.github.io/sofine/