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Bidding Engine

The RTB4FREE system is a Dockerized Open RTB bidding system. It has the basic parts needed for building a DSP. It contains a multi-bidder bidding system, a Kafka messaging system, Minio S3 compatible object store,a campaign manager, a Postgres DB, and an ElasticSearch cluster.

A basic view of the arcitecture is shown here:

arch info


Many different technologies have been tried for maintaining state information between multiple bidders and the campaign manager: Redis and Aerospike being most notable. In the end tbese technologies brought more bloat than value. What we really need is a cache between the bidders, and the campaign manager that used familiar JAVA structures, like Maps. That's exactly what Hazelcast offers for us, with its "In Memory Data Grid" IMDG.

All of the shared data needed by the bidders, is stored in the IMDG. This includes all bids, wins, campaigns, and performance statistics. Furthermore, the bidders back each other's part of the DB up.

Hazelcast is a clustered, fault tolerant customer data platform, that utilizes the standard JAVA Maplike structures. Each bidder is a hazelcast member, and ses the raft consensus protocol to create a fault tolerant database spread across clusters of datagrids. The total size of the database is limited by how many nodes you have running * the memory they have on board. Here's how the system is configured:

clusters info

The overall data base is the sum of the clustered data. In addition, the nodes back each other up, up to a limit of 6 backup nodes for each cluster.

Using the Raft consensus protocol, one Bidder is the leader, and handles all Postgres initialization as well as budgeting. Any bidder can handle Campaign manager requests, but in the end they are all handled by the Lead bidder. If that Lead bidder, goes down, the other bidders will elect a new Leader. Budgeting and campaign management activities will not be interrupted. A campaign manager connected to a non-leader would likely not even notice the change in leaders.

The IMDG architecture is quite easy to work with. An overview of its features can be seen here:

clusters info

Check out Hazelcast for more information

Campaign Manager

The campaign manager of RTB4FREE is a REACT based application that will load from any bidder. The campaign manager communicates with the Postgres database to store campaign information. Loading campaigns from Postgres into the Hazelcast cache is done by the Leader bidder running a thread called "Crosstalk".

Postgres Database

A postgres database stores all campaign definitions. The REACT-based campaign manager manipulates the postgres based tables using a well defined SQL schema, through a simple REST API to any bidder in an RTB4FREE cluster. But in reality, you can write your own RTB4FREE campaign manager by defining the appropriate tables in the SQL database and issuing the simple REST based commands to reload campaigns.

The schema for the database is located here

The ERD of the campaign manager is located here:


Data Management Platform

The Data Management Platform (DMP), the third layer of the DSP. Layer 1 is the Bidder, Layer 2 is the Campaign Manager and Layer 3 is the Data management Platform.


  • Integrated with the open source Elasticsearch, Logstash, Kibana (ELK) stack.
  • Search and view RTB transaction log details for requests, bids, wins, pixels, clicks and costs.
  • Search and view RTB application log details for bidder.
  • Out-of-the-box dashboard reports in Kibana.
  • Standard campaign metrics viewable in the Campaign Manager.
  • Create custom reports using Kibana.
  • Open architecture allows integration with your own data analytics infrastructure.
  • Standard data backup and maintenance processes included.
  • Scale up horizontally by deploying clusters for ELK and Kafka.

All bidder logs are sent to Kafka, as shown in the following diagram.

image here

The system configuration depends on many parameters, including

  • Bidder transaction rate (ie, queries per second).
  • Performance of infrastructure.
  • Available disk space.
  • Historical data retention required.
  • Granularity of data retained.

The RTB4FREE architecture can scale to support high data processing rates by horizontally scaling any of the following components:

  • Bidder servers can be added as required to support additional SSP rates.
  • Kafka, which is used for transport of data between bidders and data stores, can be clustered.
  • Kafka consumers (such as Logstash) can be partitioned to share data transfer responsibilities.
  • Elasticsearch can be clustered to accomodate increased data rates or storage requirements.

A detailed system configuration can be determined after understanding the detailed on the requirements.

Kibana Reports

The RTB log records can be searched by selecting the corresponding index from the dropdown list, then entering a Lucene query in the seach input box.

The following record types can be selected.

  • Requests. Requests for bids received from SSP exchanges.
  • Bids. Bid responses to requests. The bidder will respond if a request matches a campaign.
  • Wins. Winning bids from the exchange.
  • Pixels. Impressions that have been served, typically signaled from a pixel image.
  • Clicks. Click events.
  • Postback Events. Additional user defined events, such as video events, mobile application loads, etc.
  • Reasons. If a campaign has not bid on a request, the reason is logged here. This helps tune campaign paramters to increase win rates.
  • RTB Logs. Bidder application log, used to determine health status of bidders.
  • Stats. Bidder usage metrics, used to monitor bidder performance.

Kibana contains a report builder that lets you create various display widgets, such as charts, graphs, maps, heat maps, tag clouds, etc. A sample time series graph showing request rate over time is shown below:


You can combine various visualizations into a dashboard. This dashboard shows bidder transaction activity as well as bidder performance metrics in a single view. Any data in the logs can be visualized with these tools.


Campaign Manager Reports

Data logged into Elasticsearch can be made available to users of the Campaign Manger. The following Campaign Manager view shows each campaign's usage using data extracted from Elasticsearch.


Custom Data Stores

If you have special processing needs, you can build you own app to consume and process the data. An easy method is to build your own Kafka consumer and subscribe to the data topics you wish to process.

The open source secor project let's you read any of the RTB logs and store them in cloud storage, such as Amazon S3 or Google Cloud Storage. This option offers unlimited storage without worrying about disk space. You can then download the data for offline data analysis using tools like Hadoop.

If you need to process analytics in real time, a custom Kafka consumer can read the log stream and perform real-time analysis and store in your own database.

Hiring Us

First, and foremost, this is an open source project. If you are able to build this all yourself and run it, then this is the system for you. If you do not have Linux, AWS, JAVA, JAVASCRIPT, Docker, Kubernetes, SQL, Kafka, Elastic Search capabilities this will be more than you can handle.

This is not a turnkey system. If you want a turnkey system, have a look at Beeswax (Recently acquired by Comcast).

The code is currently going improvements. While major functionality will likely not be affected, there could be code changes that occur without notice that may break whatever modifications you have made in your own fork.

Schedule a Demo

Feel free to contact us to schedule a demonstration.

Custom Work

We can't run your DSP or be on call for support. With customizations, if your features are not something that benefits the open source community, then we generally don't take such work. We can suggest how you might accomplish your task. Custom work distracts us from the core project.

Exchange Integrations

We usually integrate with new exchanges for free, so long as you provide access to your system for integration testing. We generally don't integrate with non-RTB solutions however.

Training Available

If you do have the requisite resources available and want to integrate with RTB4FREE we can help you. We will train your developers in a week-long class, over Zoom, 8 hours day, and in your timezone. The price is $5,000 (USD).

Considering a DSP costs $250,000 to build from scratch, we think it's a bargain. If the price seems too high, then perhaps you are underestimating the effort required to build/run your own DSP.

Reporting Bugs/Fixing Bugs

If you think you found a bug, by all means please send us an email at or report it in the github repo. We reserve the right to do whatever we want with your info. We may, or may not fix the problem. If we do fix the problem, it may take some time. In any case, be specific as possible with your bug report. A bug report that says "the bidder didn't bid on my campaign" doesn't help us very much...

If you fix a bug, by all means feel free to submit a pull request to the github repo.