Cloud Dataflow is a serverless data processing service that runs jobs written using the Apache Beam libraries. When you run a job on Cloud Dataflow, it spins up a cluster of virtual machines, distributes the tasks in your job to the VMs, and dynamically scales the cluster based on how the job is performing. It may even change the order of operations in your processing pipeline to optimize your job.
So use cases are ETL (extract, transfer, load) job between various data sources / data bases. For example load big files from Cloud Storage into BigQuery.
Streaming works based on subscription to PubSub topic, so you can listen to real time events (for example from some IoT devices) and then further process.
Interesting concrete use case of Dataflow is Dataprep. Dataprep is cloud tool on GCP used for exploring, cleaning, wrangling (large) datasets. When you define actions you want to do with your data (like formatting, joining etc), job is run under the hood on Dataflow.
Cloud Dataflow also offers the ability to create jobs based on "templates," which can help simplify common tasks where the differences are parameter values.
Dataproc is a managed Spark and Hadoop service that lets you take advantage of open source data tools for batch processing, querying, streaming, and machine learning. Dataproc automation helps you create clusters quickly, manage them easily, and save money by turning clusters off when you don't need them. With less time and money spent on administration, you can focus on your jobs and your data.
- Super fast — Without using Dataproc, it can take from five to 30
minutes to create Spark and Hadoop clusters on-premises or through
IaaS providers. By comparison, Dataproc clusters are quick to start,
scale, and shutdown, with each of these operations taking 90 seconds
or less, on average. This means you can spend less time waiting for
clusters and more hands-on time working with your data.
- Integrated — Dataproc has built-in integration with other Google
Cloud Platform services, such as BigQuery, Cloud Storage, Cloud
Bigtable, Cloud Logging, and Cloud Monitoring, so you have more than
just a Spark or Hadoop cluster—you have a complete data platform.
For example, you can use Dataproc to effortlessly ETL terabytes of
raw log data directly into BigQuery for business reporting.
- Managed — Use Spark and Hadoop clusters without the assistance of an
administrator or special software. You can easily interact with
clusters and Spark or Hadoop jobs through the Google Cloud Console,
the Cloud SDK, or the Dataproc REST API. When you're done with a
cluster, you can simply turn it off, so you don’t spend money on an
idle cluster. You won’t need to worry about losing data, because
Dataproc is integrated with Cloud Storage, BigQuery, and Cloud
Bigtable.
- Simple and familiar — You don’t need to learn new tools or APIs to
use Dataproc, making it easy to move existing projects into Dataproc
without redevelopment. Spark, Hadoop, Pig, and Hive are frequently
updated, so you can be productive faster.
If you want to migrate from your existing Hadoop/Spark cluster to the cloud, or take advantage of so many well-trained Hadoop/Spark engineers out there in the market, choose Cloud Dataproc; if you trust Google's expertise in large scale data processing and take their latest improvements for free, choose DataFlow.
Here are three main points to consider while trying to choose between Dataproc and Dataflow
Provisioning
Dataproc - Manual provisioning of clusters
Dataflow - Serverless. Automatic provisioning of clusters
Hadoop Dependencies
Dataproc should be used if the processing has any dependencies to tools in the Hadoop ecosystem.
Portability
Dataflow/Beam provides a clear separation between processing logic and the underlying execution engine. This helps with portability across different execution engines that support the Beam runtime, i.e. the same pipeline code can run seamlessly on either Dataflow, Spark or Flink.