Telegraf is an open-source agent for collecting, processing, aggregating and writing metrics, logs and other data. It includes hundreds of plugins covering inputs, processors, aggregators and outputs, for example for system monitoring, cloud services, containers, IoT protocols such as MQTT and Modbus, and messaging systems such as Kafka. Telegraf compiles into a single static binary with no external dependencies and is available as a binary, a Docker image and RPM or DEB packages. Configuration is done in TOML. It is a component you run yourself rather than a hosted service.
Telegraf is developed by InfluxData, which is based in San Francisco in the United States, and is released under the MIT licence. Because you operate the agent yourself, you decide where the collected data goes: Telegraf can write to any destination, including systems inside the EU or your own infrastructure. A European organisation can therefore use Telegraf without relying on a US cloud service, and the source code is public and open to inspection.