onetl 0.12.1

Minimal installation

Base onetl package contains:

• DBReader, DBWriter and related classes

• FileDownloader, FileUploader, FileMover and related classes, like file filters & limits

• FileDFReader, FileDFWriter and related classes, like file formats

• Read Strategies & HWM classes

• Plugins support

It can be installed via:

pip install onetl

With DB and FileDF connections

All DB connection classes (Clickhouse, Greenplum, Hive and others) and all FileDF connection classes (SparkHDFS, SparkLocalFS, SparkS3) require Spark to be installed.

Firstly, you should install JDK. The exact installation instruction depends on your OS, here are some examples:

yum install java-1.8.0-openjdk-devel  # CentOS 7 + Spark 2
dnf install java-11-openjdk-devel  # CentOS 8 + Spark 3
apt-get install openjdk-11-jdk  # Debian-based + Spark 3

pip install onetl[spark]  # install latest PySpark

pip install onetl pyspark==3.5.3  # install a specific PySpark version

With File connections

All File (but not FileDF) connection classes (FTP, SFTP, HDFS and so on) requires specific Python clients to be installed.

Each client can be installed explicitly by passing connector name (in lowercase) to extras:

pip install onetl[ftp]  # specific connector
pip install onetl[ftp,ftps,sftp,hdfs,s3,webdav,samba]  # multiple connectors

To install all file connectors at once you can pass files to extras:

pip install onetl[files]

Otherwise class import will fail.

With Kerberos support

Most of Hadoop instances set up with Kerberos support, so some connections require additional setup to work properly.

• HDFS Uses requests-kerberos and GSSApi for authentication. It also uses kinit executable to generate Kerberos ticket.

• Hive and SparkHDFS require Kerberos ticket to exist before creating Spark session.

So you need to install OS packages with:

• krb5 libs

• Headers for krb5

• gcc or other compiler for C sources

The exact installation instruction depends on your OS, here are some examples:

dnf install krb5-devel gcc  # CentOS, OracleLinux
apt install libkrb5-dev gcc  # Debian-based

Also you should pass kerberos to extras to install required Python packages:

pip install onetl[kerberos]

Full bundle

To install all connectors and dependencies, you can pass all into extras:

pip install onetl[all]

# this is just the same as
pip install onetl[spark,files,kerberos]

MSSQL → Hive

Read data from MSSQL, transform & write to Hive.

# install onETL and PySpark
pip install onetl[spark]

# Import pyspark to initialize the SparkSession
from pyspark.sql import SparkSession

# import function to setup onETL logging
from onetl.log import setup_logging

# Import required connections
from onetl.connection import MSSQL, Hive

# Import onETL classes to read & write data
from onetl.db import DBReader, DBWriter

# change logging level to INFO, and set up default logging format and handler
setup_logging()

# Initialize new SparkSession with MSSQL driver loaded
maven_packages = MSSQL.get_packages()
spark = (
    SparkSession.builder.appName("spark_app_onetl_demo")
    .config("spark.jars.packages", ",".join(maven_packages))
    .enableHiveSupport()  # for Hive
    .getOrCreate()
)

# Initialize MSSQL connection and check if database is accessible
mssql = MSSQL(
    host="mssqldb.demo.com",
    user="onetl",
    password="onetl",
    database="Telecom",
    spark=spark,
    # These options are passed to MSSQL JDBC Driver:
    extra={"applicationIntent": "ReadOnly"},
).check()

# >>> INFO:|MSSQL| Connection is available

# Initialize DBReader
reader = DBReader(
    connection=mssql,
    source="dbo.demo_table",
    columns=["on", "etl"],
    # Set some MSSQL read options:
    options=MSSQL.ReadOptions(fetchsize=10000),
)

# checks that there is data in the table, otherwise raises exception
reader.raise_if_no_data()

# Read data to DataFrame
df = reader.run()
df.printSchema()
# root
#  |-- id: integer (nullable = true)
#  |-- phone_number: string (nullable = true)
#  |-- region: string (nullable = true)
#  |-- birth_date: date (nullable = true)
#  |-- registered_at: timestamp (nullable = true)
#  |-- account_balance: double (nullable = true)

# Apply any PySpark transformations
from pyspark.sql.functions import lit

df_to_write = df.withColumn("engine", lit("onetl"))
df_to_write.printSchema()
# root
#  |-- id: integer (nullable = true)
#  |-- phone_number: string (nullable = true)
#  |-- region: string (nullable = true)
#  |-- birth_date: date (nullable = true)
#  |-- registered_at: timestamp (nullable = true)
#  |-- account_balance: double (nullable = true)
#  |-- engine: string (nullable = false)

# Initialize Hive connection
hive = Hive(cluster="rnd-dwh", spark=spark)

# Initialize DBWriter
db_writer = DBWriter(
    connection=hive,
    target="dl_sb.demo_table",
    # Set some Hive write options:
    options=Hive.WriteOptions(if_exists="replace_entire_table"),
)

# Write data from DataFrame to Hive
db_writer.run(df_to_write)

# Success!

SFTP → HDFS

Download files from SFTP & upload them to HDFS.

# install onETL with SFTP and HDFS clients, and Kerberos support
pip install onetl[hdfs,sftp,kerberos]

# import function to setup onETL logging
from onetl.log import setup_logging

# Import required connections
from onetl.connection import SFTP, HDFS

# Import onETL classes to download & upload files
from onetl.file import FileDownloader, FileUploader

# import filter & limit classes
from onetl.file.filter import Glob, ExcludeDir
from onetl.file.limit import MaxFilesCount

# change logging level to INFO, and set up default logging format and handler
setup_logging()

# Initialize SFTP connection and check it
sftp = SFTP(
    host="sftp.test.com",
    user="someuser",
    password="somepassword",
).check()

# >>> INFO:|SFTP| Connection is available

# Initialize downloader
file_downloader = FileDownloader(
    connection=sftp,
    source_path="/remote/tests/Report",  # path on SFTP
    local_path="/local/onetl/Report",  # local fs path
    filters=[
        # download only files matching the glob
        Glob("*.csv"),
        # exclude files from this directory
        ExcludeDir("/remote/tests/Report/exclude_dir/"),
    ],
    limits=[
        # download max 1000 files per run
        MaxFilesCount(1000),
    ],
    options=FileDownloader.Options(
        # delete files from SFTP after successful download
        delete_source=True,
        # mark file as failed if it already exist in local_path
        if_exists="error",
    ),
)

# Download files to local filesystem
download_result = downloader.run()

# Method run returns a DownloadResult object,
# which contains collection of downloaded files, divided to 4 categories
download_result

#  DownloadResult(
#      successful=[
#          LocalPath('/local/onetl/Report/file_1.json'),
#          LocalPath('/local/onetl/Report/file_2.json'),
#      ],
#      failed=[FailedRemoteFile('/remote/onetl/Report/file_3.json')],
#      ignored=[RemoteFile('/remote/onetl/Report/file_4.json')],
#      missing=[],
#  )

# Raise exception if there are failed files, or there were no files in the remote filesystem
download_result.raise_if_failed() or download_result.raise_if_empty()

# Do any kind of magic with files: rename files, remove header for csv files, ...
renamed_files = my_rename_function(download_result.success)

# function removed "_" from file names
# [
#    LocalPath('/home/onetl/Report/file1.json'),
#    LocalPath('/home/onetl/Report/file2.json'),
# ]

# Initialize HDFS connection
hdfs = HDFS(
    host="my.name.node",
    user="someuser",
    password="somepassword",  # or keytab
)

# Initialize uploader
file_uploader = FileUploader(
    connection=hdfs,
    target_path="/user/onetl/Report/",  # hdfs path
)

# Upload files from local fs to HDFS
upload_result = file_uploader.run(renamed_files)

# Method run returns a UploadResult object,
# which contains collection of uploaded files, divided to 4 categories
upload_result

#  UploadResult(
#      successful=[RemoteFile('/user/onetl/Report/file1.json')],
#      failed=[FailedLocalFile('/local/onetl/Report/file2.json')],
#      ignored=[],
#      missing=[],
#  )

# Raise exception if there are failed files, or there were no files in the local filesystem, or some input file is missing
upload_result.raise_if_failed() or upload_result.raise_if_empty() or upload_result.raise_if_missing()

# Success!

S3 → Postgres

Read files directly from S3 path, convert them to dataframe, transform it and then write to a database.

# install onETL and PySpark
pip install onetl[spark]

# Import pyspark to initialize the SparkSession
from pyspark.sql import SparkSession

# import function to setup onETL logging
from onetl.log import setup_logging

# Import required connections
from onetl.connection import Postgres, SparkS3

# Import onETL classes to read files
from onetl.file import FileDFReader
from onetl.file.format import CSV

# Import onETL classes to write data
from onetl.db import DBWriter

# change logging level to INFO, and set up default logging format and handler
setup_logging()

# Initialize new SparkSession with Hadoop AWS libraries and Postgres driver loaded
maven_packages = SparkS3.get_packages(spark_version="3.5.3") + Postgres.get_packages()
spark = (
    SparkSession.builder.appName("spark_app_onetl_demo")
    .config("spark.jars.packages", ",".join(maven_packages))
    .getOrCreate()
)

# Initialize S3 connection and check it
spark_s3 = SparkS3(
    host="s3.test.com",
    protocol="https",
    bucket="my-bucket",
    access_key="somekey",
    secret_key="somesecret",
    # Access bucket as s3.test.com/my-bucket
    extra={"path.style.access": True},
    spark=spark,
).check()

# >>> INFO:|SparkS3| Connection is available

# Describe file format and parsing options
csv = CSV(
    delimiter=";",
    header=True,
    encoding="utf-8",
)

# Describe DataFrame schema of files
from pyspark.sql.types import (
    DateType,
    DoubleType,
    IntegerType,
    StringType,
    StructField,
    StructType,
    TimestampType,
)

df_schema = StructType(
    [
        StructField("id", IntegerType()),
        StructField("phone_number", StringType()),
        StructField("region", StringType()),
        StructField("birth_date", DateType()),
        StructField("registered_at", TimestampType()),
        StructField("account_balance", DoubleType()),
    ],
)

# Initialize file df reader
reader = FileDFReader(
    connection=spark_s3,
    source_path="/remote/tests/Report",  # path on S3 there *.csv files are located
    format=csv,  # file format with specific parsing options
    df_schema=df_schema,  # columns & types
)

# Read files directly from S3 as Spark DataFrame
df = reader.run()

# Check that DataFrame schema is same as expected
df.printSchema()
# root
#  |-- id: integer (nullable = true)
#  |-- phone_number: string (nullable = true)
#  |-- region: string (nullable = true)
#  |-- birth_date: date (nullable = true)
#  |-- registered_at: timestamp (nullable = true)
#  |-- account_balance: double (nullable = true)

# Apply any PySpark transformations
from pyspark.sql.functions import lit

df_to_write = df.withColumn("engine", lit("onetl"))
df_to_write.printSchema()
# root
#  |-- id: integer (nullable = true)
#  |-- phone_number: string (nullable = true)
#  |-- region: string (nullable = true)
#  |-- birth_date: date (nullable = true)
#  |-- registered_at: timestamp (nullable = true)
#  |-- account_balance: double (nullable = true)
#  |-- engine: string (nullable = false)

# Initialize Postgres connection
postgres = Postgres(
    host="192.169.11.23",
    user="onetl",
    password="somepassword",
    database="mydb",
    spark=spark,
)

# Initialize DBWriter
db_writer = DBWriter(
    connection=postgres,
    # write to specific table
    target="public.my_table",
    # with some writing options
    options=Postgres.WriteOptions(if_exists="append"),
)

# Write DataFrame to Postgres table
db_writer.run(df_to_write)

# Success!