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205 lines
6.6 KiB
Markdown
205 lines
6.6 KiB
Markdown
# Introduction
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This project implements an abstraction of objects that can have access to a variety of data stores, implementing read/write with a simple and expressive interface. This abstraction works with **NoSQL** and **SQL** data stores and leverages **pandas**.
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The supported data store providers :
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| Provider | Underlying Drivers | Description |
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| :---- | :----: | ----: |
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| sqlite| Native SQLite|SQLite3|
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| postgresql| psycopg2 | PostgreSQL
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| redshift| psycopg2 | Amazon Redshift
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| s3| boto3 | Amazon Simple Storage Service
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| netezza| nzpsql | IBM Neteeza
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| Files: CSV, TSV| pandas| pandas data-frame
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| Couchdb| cloudant | Couchbase/Couchdb
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| mongodb| pymongo | Mongodb
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| mysql| mysql| Mysql
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| bigquery| google-bigquery| Google BigQuery
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| mariadb| mysql| Mariadb
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| rabbitmq|pika| RabbitMQ Publish/Subscribe
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# Why Use Data-Transport ?
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Mostly data scientists that don't really care about the underlying database and would like to manipulate data transparently.
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1. Familiarity with **pandas data-frames**
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2. Connectivity **drivers** are included
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3. Mining data from various sources
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4. Useful for data migrations or ETL
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# Usage
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## Installation
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Within the virtual environment perform the following :
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pip install git+https://dev.the-phi.com/git/steve/data-transport.git
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Once installed **data-transport** can be used as a library in code or a command line interface (CLI), as a CLI it is used for ETL and requires a configuration file.
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## Data Transport as a Library (in code)
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---
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The data-transport can be used within code as a library, and offers the following capabilities:
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* Read/Write against [mongodb](https://github.com/lnyemba/data-transport/wiki/mongodb)
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* Read/Write against tranditional [RDBMS](https://github.com/lnyemba/data-transport/wiki/rdbms)
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* Read/Write against [bigquery](https://github.com/lnyemba/data-transport/wiki/bigquery)
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* ETL CLI/Code [ETL](https://github.com/lnyemba/data-transport/wiki/etl)
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* Support for pre/post conditions i.e it is possible to specify queries to run before or after a read or write
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The read/write functions make data-transport a great candidate for **data-science**; **data-engineering** or all things pertaining to data. It enables operations across multiple data-stores(relational or not)
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## ETL
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**Embedded in Code**
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It is possible to perform ETL within custom code as follows :
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```
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import transport
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import time
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_info = [{source:{'provider':'sqlite','path':'/home/me/foo.csv','table':'me',"pipeline":{"pre":[],"post":[]}},target:{provider:'bigquery',private_key='/home/me/key.json','table':'me','dataset':'mydataset'}}, ...]
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procs = transport.factory.instance(provider='etl',info=_info)
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#
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#
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while procs:
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procs = [pthread for pthread in procs if pthread.is_alive()]
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time.sleep(1)
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```
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**Command Line Interface (CLI):**
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---
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The CLI program is called **transport** and it requires a configuration file. The program is intended to move data from one location to another. Supported data stores are in the above paragraphs.
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```
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[
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{
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"id":"logs",
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"source":{
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"provider":"postgresql","context":"read","database":"mydb",
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"cmd":{"sql":"SELECT * FROM logs limit 10"}
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},
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"target":{
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"provider":"bigquery","private_key":"/bgqdrive/account/bq-service-account-key.json",
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"dataset":"mydataset"
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}
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},
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]
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```
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Assuming the above content is stored in a file called **etl-config.json**, we would perform the following in a terminal window:
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```
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[steve@data-transport]$ transport --config ./etl-config.json [--index <value>]
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```
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**Reading/Writing Mongodb**
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For this example we assume here we are tunneling through port 27018 and there is not access control:
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```
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import transport
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reader = factory.instance(provider='mongodb',context='read',host='localhost',port='27018',db='example',doc='logs')
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df = reader.read() #-- reads the entire collection
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print (df.head())
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#
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#-- Applying mongodb command
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PIPELINE = [{"$group":{"_id":None,"count":{"$sum":1}}}]
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_command_={"cursor":{},"allowDiskUse":True,"aggregate":"logs","pipeline":PIPLINE}
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df = reader.read(mongo=_command)
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print (df.head())
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reader.close()
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```
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**Read/Writing to Mongodb**
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---
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Scenario 1: Mongodb with security in place
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1. Define an authentication file on disk
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The semantics of the attributes are provided by mongodb, please visit [mongodb documentation](https://mongodb.org/docs). In this example the file is located on _/transport/mongo.json_
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<div style="display:grid; grid-template-columns:60% auto; gap:4px">
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<div>
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<b>configuration file</b>
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```
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{
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"username":"me","password":"changeme",
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"mechanism":"SCRAM-SHA-1",
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"authSource":"admin"
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}
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```
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<b>Connecting to Mongodb </b>
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```
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import transport
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PIPELINE = ... #-- do this yourself
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MONGO_KEY = '/transport/mongo.json'
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mreader = transport.factory.instance(provider=transport.providers.MONGODB,auth_file=MONGO_KEY,context='read',db='mydb',doc='logs')
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_aggregateDF = mreader.read(mongo=PIPELINE) #--results of a aggregate pipeline
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_collectionDF= mreader.read()
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```
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In order to enable write, change **context** attribute to **'read'**.
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</div>
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<div>
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- The configuration file is in JSON format
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- The commands passed to mongodb are the same as you would if you applied runCommand in mongodb
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- The output is a pandas data-frame
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- By default the transport reads, to enable write operations use **context='write'**
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|parameters|description |
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| --- | --- |
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|db| Name of the database|
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|port| Port number to connect to
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|doc| Name of the collection of documents|
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|username|Username |
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|password|password|
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|authSource|user database that has authentication info|
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|mechanism|Mechnism used for authentication|
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**NOTE**
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Arguments like **db** or **doc** can be placed in the authentication file
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</div>
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</div>
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**Limitations**
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Reads and writes aren't encapsulated in the same object, this is to allow the calling code to deliberately perform actions and hopefully minimize accidents associated with data wrangling.
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```
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import transport
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improt pandas as pd
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writer = factory.instance(provider=transport.providers.MONGODB,context='write',host='localhost',port='27018',db='example',doc='logs')
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df = pd.DataFrame({"names":["steve","nico"],"age":[40,30]})
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writer.write(df)
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writer.close()
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```
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#
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# reading from postgresql
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pgreader = factory.instance(type='postgresql',database=<database>,table=<table_name>)
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pg.read() #-- will read the table by executing a SELECT
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pg.read(sql=<sql query>)
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#
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# Reading a document and executing a view
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#
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document = dreader.read()
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result = couchdb.view(id='<design_doc_id>',view_name=<view_name',<key=value|keys=values>)
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