com.qiniu:stream-cassandra

Introduction

QStreaming is a framework that simplifies writing and executing ETLs on top of Apache Spark

It is based on a simple sql-like configuration file and runs on any Spark cluster

Getting started

Configurations

To run QStreaming you must first define Pipeline DSL file as below.

Pipeline DSL

For example a simple pipeline dsl file should be as follows:

-- DDL for streaming input which connect to a kafka topic
-- this declares five fields based on the JSON data format.In addition, it use the ROWTIME() to declare a virtual column that generate the event time attribute from existing ts field
create stream input table user_behavior(
  user_id LONG,
  item_id LONG,
  category_id LONG,
  behavior STRING,
  ts TIMESTAMP,
  eventTime as ROWTIME(ts,'1 minutes')
) using kafka(
  kafka.bootstrap.servers="localhost:localhost:9091",
  startingOffsets=earliest,
  subscribe="user_behavior",
  "group-id"="user_behavior"
);

-- DDL for streaming output which connect to a kafka topic
create stream output table behavior_cnt_per_hour
using kafka(
  kafka.bootstrap.servers="localhost:9091",
  topic="behavior_cnt_per_hour"
)TBLPROPERTIES(
  "update-mode"="update",
  checkpointLocation = "behavior_cnt_per_hour"
);

-- CREATE VIEW count the number of "buy" records in each hour window.
create view v_behavior_cnt_per_hour as
SELECT
   window(eventTime, "1 minutes") as window,
   COUNT(*) as behavior_cnt,
   behavior
FROM user_behavior
GROUP BY
  window(eventTime, "1 minutes"),
  behavior;

--  persist metric to kafka
insert into behavior_cnt_per_hour
select
   from_unixtime(cast(window.start as LONG)/1000,'yyyy-MM-dd HH:mm') as time,
   behavior_cnt,
   behavior
from
  v_behavior_cnt_per_hour;

Run QStreaming

There are three options to run QStreaming, first to get the latest released JAR from here

Run on a yarn cluster

To run on a cluster requires Apache Spark v2.2+

• Run the following command:

$SPARK_HOME/bin/spark-submit
--class com.qiniu.stream.core.Streaming \
--master yarn \
--deploy-mode client \
stream-standalone-0.1.0-jar-with-dependencies.jar  \
-j pathToYourPipeline.dsl 

Run on a standalone cluster

To run on a standalone cluster you must first start a spark standalone cluster , and then run the following command:

$SPARK_HOME/bin/spark-submit
--class com.qiniu.stream.core.Streaming \
--master spark://IP:PORT \
stream-standalone-0.1.0-jar-with-dependencies.jar \
-j pathToYourPipeline.dsl 

Run as a library

It's also possible to use QStreaming inside your own project

To use it adds the dependency to your project

• maven

  <dependency>
    <groupId>com.qiniu</groupId>
    <dependency>stream-core</dependency>
    <version>0.1.0</version>
  </dependency>
  

• gradle

  compile 'com.qiniu:stream-core:0.1.0'
  

• sbt

  libraryDependencies += "com.qiniu" % "stream-core" % "0.1.0"

Datasources

• Kafka
• HDFS/S3
• Jdbc
• MongoDB
• HBase
• Cassandra
• Elasticsearch
• Hudi
• Redis

Features

DDL enhancement

QStreaming allow to connect to a stream source with DDL statement.

For example below define an input which connect to a kafka topic

create stream input table user_behavior(
  user_id LONG,
  item_id LONG,
  category_id LONG,
  behavior STRING,
  ts TIMESTAMP,
  eventTime as ROWTIME(ts,'1 minutes')
) using kafka(
  kafka.bootstrap.servers="localhost:9091",
  startingOffsets=earliest,
  subscribe="user_behavior",
  "group-id"="user_behavior"
);

Please refer to CreateSourceTableStatement and CreateSinkTableStatement for the detail of DDL statement .

Watermark support

QStreaming supports watermark which helps a stream processing engine to deal with late data.

There are two ways to use watermark for a stream processing engine

• Adding ROWTIME(eventTimeField,delayThreshold) as a schema property in a ddl statement

  create stream input table user_behavior(
    user_id LONG,
    item_id LONG,
    category_id LONG,
    behavior STRING,
    ts TIMESTAMP,
    eventTime as ROWTIME(ts,'1 minutes')
  ) using kafka(
    kafka.bootstrap.servers="localhost:9091",
    startingOffsets=earliest,
    subscribe="user_behavior",
    "group-id"="user_behavior"
  );

  Above example means use eventTime as event time field with 5 minutes delay thresholds

• Adding waterMark("eventTimeField, delayThreshold") as a view property in a view statement

  create view v_behavior_cnt_per_hour(waterMark = "eventTime, 1 minutes") as
  SELECT
     window(eventTime, "1 minutes") as window,
     COUNT(*) as behavior_cnt,
     behavior
  FROM user_behavior
  GROUP BY
    window(eventTime, "1 minutes"),
    behavior;

Above example define a watermark use eventTime field with 1 minute threshold

Dynamic user define function

-- define UDF named hello
create function hello(name:String) = {
   s"hello ${name}"
};

QStreaming allow to define a dynamic UDF inside job.dsl, for more detail information please refer to createFunctionStatement

Above example define UDF with a string parameter.

Multiple sink

QStreaming allow you to define multiple output for streaming process by leavarage foreEachBatch mode (only avaliable in spark>=2.4.0)

Below example will sink the behavior count metric to two kafka topics

    create stream output table output using kafka(
        kafka.bootstrap.servers=<kafkaBootStrapServers>,
        topic="topic1" 
    ),kafka(
        kafka.bootstrap.servers=<kafkaBootStrapServers>,
        topic="topic2" 
    ) TBLPROPERTIES (outputMode = update,checkpointLocation = "behavior_output");

For more information about how to create multiple sink please refer to createSinkTableStatement

Variable interpolation

QStreaming support variable interpolation from command line arguments , this is useful for running QStreaming as a periodic job, and referece them in sql file .

For example, you can pass the value for theDayThatRunAJob and theHourThatRunAJob from an Airflow DAG

$SPARK_HOME/bin/spark-submit
--name yourAppName \
--class com.qiniu.stream.core.Streaming \
stream-standalone-0.1.0-jar-with-dependencies.jar \
-j pathToYourPipeline.dsl \
-v day=theDayThatRunAJob \
-v hour=theHourThatRunAJob

and the pipeline dsl file

create batch input table raw_log
USING parquet(path="hdfs://cluster1/logs/day=${day}/hour=${hourt");

Monitor

Kafka lag monitor

QStreaming allow to monitor the kafka topic offset lag by adding the "group-id" connector property in ddl statement as below

create stream input table user_behavior(
  user_id LONG,
  item_id LONG,
  category_id LONG,
  behavior STRING,
  ts TIMESTAMP,
  eventTime as ROWTIME(ts,'1 minutes')
) using kafka(
  kafka.bootstrap.servers="localhost:9091",
  startingOffsets=earliest,
  subscribe="user_behavior",
  "group-id"="user_behavior"
);

Data Quality Check

The purpose is to "unit-test" data to find errors early, before the data gets fed to any storage.

For example, we test for the following properties of data :

• there are 5 rows in total
• values of the id attribute are never NULL and unique
• values of the productName attribute are never NULL
• the priority attribute can only contain "high" or "low" as value
• numViews should not contain negative values
• at least half of the values in description should contain a url
• the median of numViews should be less than or equal to 10

In DSL this looks as follows:

CREATE TEST testName(testLevel=Error,testOutput=testResult) on dataset WITH 
   numRows()=5 and 
   isNotNull(id) and 
   isUnique(id) and 
   isComplete(productName) and 
   isContainedIn(priority, ["high", "low"]) and 
   isNonNegative(numViews)  and 
   containsUrl(description) >= 0.5 and 
   hasApproxQuantile（numViews, 0.5) <= 10

Architecture

Blogs

• QStreaming-轻量级ETL开发框架

License

See the LICENSE file for license rights and limitations (Apache License).