Hadoop

The early data ingestion pipeline at Pinterest used Kafka as the central message transporter, with the app servers writing messages directly to Kafka, which then uploaded log files to S3.

For databases, a custom Hadoop streamer pulled database data and wrote it to S3.

Challenges cited for this infrastructure included high operational overhead, as well as potential data loss occurring when Kafka broker outages led to an overflow of in-memory message buffering.

Why we built Marmaray, an open source generic data ingestion and dispersal framework and library for Apache Hadoop :

Built and designed by our Hadoop Platform team, Marmaray is a plug-in-based framework built on top of the Hadoop ecosystem. Users can add support to ingest data from any source and disperse to any sink leveraging the use of Apache Spark . The name, Marmaray, comes from a tunnel in Turkey connecting Europe and Asia. Similarly, we envisioned Marmaray within Uber as a pipeline connecting data from any source to any sink depending on customer preference:

https://eng.uber.com/marmaray-hadoop-ingestion-open-source/

(Direct GitHub repo: https://github.com/uber/marmaray Kafka Kafka Manager )

By mid-2014, around the time of the Series F, Pinterest users had already created more than 30 billion Pins, and the company was logging around 20 terabytes of new data daily, with around 10 petabytes of data in S3. To drive personalization for its users, and to empower engineers to build big data applications quickly, the data team built a self-serve Hadoop platform.

To start, they decoupled compute from storage, which meant teams would have to worry less about loading or synchronizing data, allowing existing or future clusters to make use of the data across a single shared file system.

A centralized Hive metastore act as the source of truth. They chose Hive for most of their Hadoop jobs “primarily because the SQL interface is simple and familiar to people across the industry.”

Dependency management takes place across three layers: *** Baked AMIs, which are large slow-loading dependencies pre-loaded on images; **Automated Configurations (Masterless Puppets), which allows Puppet clients to “pull their configuration from S3 and set up a service that’s responsible for keeping S3 configurations in sync with the Puppet master;” and Runtime Staging on S3, which creates a working directory at runtime for each developer that pulls down its dependencies directly from S3.

Finally, they migrated their Hadoop jobs to Qubole, which “supported AWS/S3 and was relatively easy to get started on.”

With interactions across each other and mobile devices, logging is important as it is information for internal cases like debugging and business cases like dynamic pricing.

With multiple Kafka clusters, data is archived into Hadoop before expiration. Data is ingested in realtime and indexed into an ELK stack. The ELK stack comprises of Elasticsearch, Logstash, and Kibana for searching and visualization.

To improve platform scalability and efficiency, Uber transitioned from JSON to Parquet, and built a central schema service to manage schemas and integrate different client libraries.

While the first generation big data platform was vulnerable to upstream data format changes, “ad hoc data ingestions jobs were replaced with a standard platform to transfer all source data in its original, nested format into the Hadoop data lake.”

These platform changes enabled the scaling challenges Uber was facing around that time: “On a daily basis, there were tens of terabytes of new data added to our data lake, and our Big Data platform grew to over 10,000 vcores with over 100,000 running batch jobs on any given day.”

Around 2015, the growing use of Uber’s data exposed limitations in the ETL and Vertica-centric setup, not to mention the increasing costs. “As our company grew, scaling our data warehouse became increasingly expensive. To cut down on costs, we started deleting older, obsolete data to free up space for new data.”

To overcome these challenges, Uber rebuilt their big data platform around Hadoop. “More specifically, we introduced a Hadoop data lake where all raw data was ingested from different online data stores only once and with no transformation during ingestion.”

“In order for users to access data in Hadoop, we introduced Presto to enable interactive ad hoc user queries, Apache Spark to facilitate programmatic access to raw data (in both SQL and non-SQL formats), and Apache Hive to serve as the workhorse for extremely large queries.