Easy ETL
Project description
Glide: Easy ETL
Introduction
Glide is an easy-to-use data pipelining tool inspired by Consecution and Apache Storm Topologies.
Like those libraries, Glide is:
- A simple, reusable approach to building robust ETL pipelines
- A system for wiring together processing nodes to form a directed acyclic graph (DAG)
Glide also has:
- An expanding suite of built-in nodes and pipelines that extract, transform, and load data from/to any combination of:
- SQL databases (SQLite, DBAPI, and SQLAlchemy support)
- Local or remote files (CSVs, Excel, and raw file support)
- URLs (JSON endpoints, file downloads, APIs, etc.)
- HTML Tables
- Emails
- Extensions for Pandas, Dask, Celery, Redis Queue and more
- A variety of node and DAG parallel/concurrent/distributed processing strategies
- A simple decorator to generate a command line interface from a pipeline in ~one line of code
- Flexible pipeline templating
Glide is not a task orchestration and/or dependency management tool like Airflow. Use Glide to define your easily developed/contained/reusable/testable data processing pipelines and then rely on a tool like Airflow to do what it's good at, namely scheduling and complex task dependency management.
Table of Contents
- Installation
- Primer
- Basic Examples
- Flow Control Examples
- Parallelization & Concurrency
- Utility Examples
- CLI Generation
- Extensions
- Docs
- How to Contribute
Installation
⚠️ Warning: This project is in an alpha state and is maintained on an as-needed basis. Please test carefully for production usage and report any issues.
$ pip install glide
Primer
You are encouraged to take a deeper look at the docs, but the short of it is the following:
1. A Node is a part of a pipeline which has a run method that typically
accepts data from upstream nodes, and pushes data to downstream nodes. For example:
class MyNode(Node):
def run(self, data):
# Some node-specific code here
self.push(data)
2. A Glider is a pipeline of Node objects wired together in a DAG. It
accepts input data in its consume method. For example:
glider = Glider(
MyExtractNode("extract")
| MyTransformNode("transform")
| MyLoadNode("load")
)
glider.consume(data)
If a node's run method has additional parameters, they are populated from
the node's context. More info on creating nodes and populating runtime context
can be found here.
Basic Examples
The following examples serve to quickly illustrate some core features and
built-in nodes. There is much more Glide can do that is not shown
here. Everything below assumes you have used the following shortcut to import
all necessary node and pipeline classes:
from glide import *
Example: CSV Extract, Transform, and Load
Apply a transformation to data from a CSV, use a function to lowercase all strings, and load into an output CSV:
def lower_rows(data):
for row in data:
for k, v in row.items():
row[k] = v.lower() if type(v) == str else v
return data
glider = Glider(
CSVExtract("extract")
| Func("transform", func=lower_rows)
| CSVLoad("load")
)
glider.consume(
["/path/to/infile.csv"],
extract=dict(chunksize=100),
load=dict(outfile="/path/to/outfile.csv"),
)
Example: SQL Extract and Load
Read from one table, write to another:
conn = get_my_sqlalchemy_conn()
sql = "select * from in_table limit 10"
glider = Glider(
SQLExtract("extract")
| SQLLoad("load"),
global_state=dict(conn=conn) # conn is automagically passed to any nodes that accept a "conn" argument
)
glider.consume(
[sql],
load=dict(table="out_table")
)
Example: SQL Transactions
Start a transaction before writing to a database, rollback on failure:
glider = Glider(
SQLExtract("extract")
| SQLTransaction("tx")
| SQLLoad("load", rollback=True),
global_state=dict(conn=conn)
)
glider.consume(...)
Example: URL Extraction
Extract data from each URL in the list of requests and load to a URL endpoint:
glider = Glider(URLExtract("extract") | URLLoad("load"))
reqs = [
"https://jsonplaceholder.typicode.com/todos/1",
"https://jsonplaceholder.typicode.com/todos/2",
]
glider.consume(
reqs,
extract=dict(data_type="json"),
load=dict(
url="https://jsonplaceholder.typicode.com/todos",
data_param="json",
headers={"Content-type": "application/json; charset=UTF-8"},
),
)
Flow Control Examples
Example: Filters
Filter the propagation of data based on the result of a function:
def data_check(node, data):
# do some check on data, return True/False to control filtering
return True
glider = Glider(
MyExtract("extract")
| Filter("filter", func=data_check)
| MyLoad("load")
)
Example: IterPush
Push each row of an input iterable individually:
glider = Glider(
CSVExtract("extract", nrows=20)
| IterPush("iter")
| Print("load")
)
Example: SplitPush
Split an iterable before pushing:
glider = Glider(SplitPush("push", split_count=2) | Print("print"))
glider.consume([range(4)])
Example: SplitByNode
Split an iterable evenly among downstream nodes:
glider = Glider(SplitByNode("push") | [Print("print1"), Print("print2")])
glider.consume([range(4)])
Example: Reduce
Collect all upstream node data before pushing:
glider = Glider(
CSVExtract("extract")
| Reduce("reduce")
| Print("load")
)
glider.consume(["/path/to/infile1.csv", "/path/to/infile2.csv"])
This will read both input CSVs and push them in a single iterable to the
downstream nodes. You can also use the flatten option of Reduce to
flatten the depth of the iterable before pushing (effectively a concat
operation).
Example: Join
Join data on one or more columns before pushing:
glider = Glider(
Reduce("reduce")
| Join("join")
| Print("load")
)
d1 = <list of dicts or DataFrame>
d2 = <list of dicts or DataFrame>
glider.consume([d1, d2], join=dict(on="common_key", how="inner"))
Example: Routers
Route data to a particular downstream node using a router function:
def parity_router(row):
if int(row["mycolumn"]) % 2 == 0:
return "even"
return "odd"
glider = Glider(
CSVExtract("extract", nrows=20)
| IterPush("iter")
| [parity_zip_router, Print("even"), Print("odd")]
)
glider.consume(...)
This will push rows with even mycolumn values to the "even" Print node,
and rows with odd mycolumn values to the "odd" Print node.
Example: Window Processing
Push a sliding window of the data:
glider = Glider(
CSVExtract("extract", nrows=5)
| WindowPush("window", size=3)
| MyWindowCalcNode("calc")
)
Example: Date Windows
Generate a set of datetime windows and push them downstream:
import datetime
today = datetime.date.today()
glider = Glider(DateTimeWindowPush("windows") | PrettyPrint("print"))
glider.consume(
windows=dict(
start_date=today - datetime.timedelta(days=3),
end_date=today,
num_windows=2
)
)
Or use DateWindowPush for date objects. Note that the data arg to consume
can be ignored because the top node (DateTimeWindowPush) is a subclass of
NoInputNode which takes no input data and generates data to push
on its own.
Example: Return Values
By default consume does not return any values and assumes you will be
outputting your results to one or more endpoints in your terminating
nodes (files, databases, etc.). The Return node will collect the data
from its parent node(s) and set it as a return value for consume.
glider = Glider(
CSVExtract("extract")
| MyTransformer("transform")
| Return("return")
)
data = glider.consume(...)
Parallelization & Concurrency
Example: Parallel Transformation
Call a function in parallel processes on equal splits of data from a CSV:
glider = Glider(
CSVExtract("extract")
| ProcessPoolSubmit("transform", push_type=PushTypes.Result)
| CSVLoad("load")
)
glider.consume(
["infile.csv"],
transform=dict(func=lower_rows),
load=dict(outfile="outfile.csv"),
)
We passed push_type=PushTypes.Result to force ProcessPoolSubmit to fetch
and combine the asynchronous results before pushing to the downstream
node. The default is to just pass the asynchronous task/futures objects
forward, so the following would be equivalent:
glider = Glider(
CSVExtract("extract")
| ProcessPoolSubmit("transform")
| FuturesReduce("reduce")
| Flatten("flatten")
| CSVLoad("load")
)
The FuturesReduce node waits for the results from each futures object, and
then Flatten will combine each subresult back together into a single result
to be loaded in the final CSVLoad node.
Example: Parallel Pipelines via ParaGlider
Completely parallelize a pipeline using a ParaGlider (who said ETL isn't
fun?!?). Split processing of the inputs (two files in this case) over the
pool, with each process running the entire pipeline on part of the consumed
data:
glider = ProcessPoolParaGlider(
CSVExtract('extract')
| Print('load')
)
glider.consume(
["/path/to/infile1.csv", "/path/to/infile2.csv"],
extract=dict(nrows=50)
)
Example: Parallel Branching
Branch into parallel execution in the middle of the DAG utilizing a parallel push node:
glider = Glider(
CSVExtract("extract", nrows=60)
| ProcessPoolPush("push", split=True)
| [Print("load1"), Print("load2"), Print("load3")]
)
glider.consume(["/path/to/infile.csv"])
The above example will extract 60 rows from a CSV and then push equal slices
to the logging nodes in parallel processes. Using split=False (default)
would have passed the entire 60 rows to each logging node in parallel
processes.
Once you branch off into processes with a parallel push node there is no way to reduce/join the pipeline back into the original process and resume single-process operation. The entire remainder of the pipeline is executed in each subprocess. However, that is possible with threads as shown in the next example.
Example: Thread Reducers
glider = Glider(
CSVExtract("extract", nrows=60)
| ThreadPoolPush("push", split=True)
| [Print("load1"), Print("load2"), Print("load3")]
| ThreadReduce("reduce")
| Print("loadall")
)
glider.consume(["/path/to/infile.csv"])
The above code will split the data and push to the first 3 logging nodes in
multiple threads. The ThreadReduce node won't push until all of the previous
nodes have finished, and then the final logging node will print all of the
results.
Example: Asyncio
Limited, experimental support is also available for concurrency via asyncio
in Python >= 3.7:
import asyncio
async def async_sleep(data):
# Dummy example. Await some real async work in here.
await asyncio.sleep(0.5)
return data
glider = Glider(
CSVExtract("extract", nrows=5)
| AsyncIOSubmit("transform", push_type=PushTypes.Result)
| Print("load")
)
glider.consume(
["/path/to/infile.csv"],
transform=dict(func=async_sleep)
)
The above example will split the input data into items to be processed on an
asyncio event loop and synchronously wait for the results before pushing.
AsyncIOSubmit supports specifying a split_count as well as a timeout
when waiting for results. Alternatively, one can push asyncio futures and
later reduce their results as follows:
glider = Glider(
CSVExtract("extract", nrows=5)
| AsyncIOSubmit("transform", push_type=PushTypes.Async)
| AsyncIOFuturesReduce("reduce", flatten=True)
| Print("load")
)
Note that the asyncio nodes will create and start an event loop for you if
necessary. It's also perfectly fine to manage the event loop on your own, in
which case glide will run tasks on the current thread's event loop.
Utility Examples
Example: Templated Nodes and Pipelines
Drop replacement nodes into an existing pipeline. Any node can be replaced by name:
glider = Glider(
PlaceholderNode("extract")
| CSVLoad("load")
)
glider["extract"] = CSVExtract("extract")
glider.consume(...)
Or reuse an existing structure of nodes with a NodeTemplate:
nodes = NodeTemplate(
CSVExtract("extract")
| CSVLoad("load")
)
glider = Glider(nodes()) # Copy of nodes created with each call
Or reuse an existing pipeline structure with GliderTemplate:
template = GliderTemplate(
CSVExtract("extract")
| CSVLoad("load")
)
glider = template() # Copy of pipeline created with each call
Example: Data Integrity Checks
You can use the AssertFunc node to assert that some condition of the data is
met:
glider = Glider(
CSVExtract("extract", chunksize=10, nrows=20)
| AssertFunc("length_check", func=lambda node, data: len(data) == 10)
| CSVLoad("load")
)
The func callable must accept two parameters, a reference to the node object
and the data passed into that node. Any truthy value returned will pass the
assertion test.
Similarly, you can do a sql-based check with AssertSQL, in this case simply
verifying the number of rows inserted:
glider = Glider(
SQLExtract("extract")
| SQLLoad("load")
| AssertSQL("sql_check")
)
sql = "select * from in_table limit 10"
assert_sql = "select (select count(*) as x from out_table) == 10 as assert"
glider.consume(
[sql],
extract=dict(conn=in_conn),
load=dict(conn=out_conn, table="out_table"),
sql_check=dict(conn=out_conn, sql=assert_sql)
)
This looks for a truthy value in the assert column of the result to pass the
assertion. You can also use the data_check option of AssertSQL to instead
have it do a comparison to the result of some function of the data:
glider = ...
sql = "select * from in_table limit 10"
assert_sql = "select count(*) as assert from out_table"
glider.consume(
[sql],
extract=dict(conn=in_conn),
load=dict(conn=out_conn, table="out_table", push_data=True),
sql_check=dict(
conn=out_conn,
sql=assert_sql,
data_check=lambda node, data: len(data)
)
)
Note that we also added push_data=True to the SQLLoad node to have it push
the data instead of a table name.
Example: Debugging
To enable debug logging for Glide change the log level of the "glide" logger:
import logging
logging.getLogger("glide").setLevel(logging.DEBUG)
Glide will then print debug information about data passed through your pipeline.
You can also pass _log=True to the init method of any node to enable logging
of processed data:
glider = Glider(
SQLExtract("extract", _log=True)
...
)
Additionaly, you can pass _debug=True to the init method of any node to
cause the node to drop into PDB right before calling run, assuming you
aren't executing the pipeline in a subprocess:
glider = Glider(
SQLExtract("extract", _debug=True)
...
)
Finally, there are a variety of print nodes you can place in your pipeline for
general logging or debugging, such as Print, PrettyPrint, LenPrint,
ReprPrint, and FormatPrint. See the node documentation for more info.
Example: Profiling Pipelines
Insert a Profile node somewhere in your pipeline to get profiler information
for all downstream nodes:
glider = Glider(
Profile("profile")
...
)
Example: Complex Pipelines
If the hierarchy of nodes you want to form is not achievable with the |
operator, you can use the add_downstream Node method to form more complex
graphs. More info can be found
here.
Example: Plotting Pipeline DAGs
If you have the Graphviz package installed, you can generate a plot of your pipelines by simply doing the following:
glider = Glider(...)
glider.plot("/path/to/filename.png")
CLI Generation
With Glide you can create parameterized command line scripts from any pipeline with a simple decorator:
glider = Glider(
SQLLoad("extract")
| SQLExtract("load")
)
@glider.cli()
def main(glide_data, node_contexts):
glider.consume(glide_data, **node_contexts)
if __name__ == "__main__":
main()
The script arguments, their types, and whether they are required or not is all
inferred by inspecting the run arguments on the nodes of the pipeline and
prefixing the node name. Please see the full documentation
here
for more details.
Extensions
To install all extensions and dev dependencies:
$ pip install glide[complete]
You can also just install Glide plus a specific extension:
$ pip install glide[dask]
$ pip install glide[celery]
$ pip install glide[rq]
$ pip install glide[swifter]
To access installed extensions import from the glide.extensions submodules
as necessary. Review the documentation and tests for current extensions for
help getting started.
Pandas
The Pandas extension is actually supported by default with all glide installs.
Below is a simple example that extracts from a CSV, lowercases all strings,
and then loads to another CSV using Pandas under the hood:
def lower(s):
return s.lower() if type(s) == str else s
glider = Glider(
DataFrameCSVExtract("extract")
| DataFrameApplyMap("transform", func=lower)
| DataFrameCSVLoad("load", index=False, mode="a")
)
glider.consume(...)
There are a variety of other helpful nodes built in, including ToDataFrame,
FromDataFrame, nodes to read/write other datasources, and nodes to deal with
rolling calculations. There is also a generic DataFrameMethod node that
passes through to any DataFrame method.
See the extension docs here for node/pipeline reference information. See the tests here for some additional examples.
Dask - Experimental
See the extension docs here for node/pipeline reference information. See the tests here for some additional examples.
Celery - Experimental
See the extension docs here for node/pipeline reference information. See the tests here for some additional examples.
Redis Queue - Experimental
See the extension docs here for node/pipeline reference information. See the tests here for some additional examples.
Swifter - Experimental
See the extension docs here for node/pipeline reference information. See the tests here for some additional examples.
Documentation
More thorough documentation can be found here. You can supplement your knowledge by perusing the tests directory or the module reference.
How to Contribute
See the CONTRIBUTING guide.
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