OpenTSDB vs PipelineDB: What are the differences?
OpenTSDB: A scalable time series database. It is a distributed, scalable time series database to store, index & serve metrics collected from computer systems at a large scale. It can store and serve massive amounts of time series data without losing granularity; PipelineDB: The Streaming SQL Database. PipelineDB is an open-source relational database that runs SQL queries continuously on streams, incrementally storing results in tables.
OpenTSDB and PipelineDB can be categorized as "Databases" tools.
OpenTSDB is an open source tool with 4.03K GitHub stars and 1.18K GitHub forks. Here's a link to OpenTSDB's open source repository on GitHub.