blackbox_exporter

The Blackbox Exporter is a monitoring tool that checks whether external services are reachable and working. It is part of the Prometheus monitoring ecosystem, which collects and stores measurements about systems so teams can track their health over time.

The name "blackbox" describes the approach: the tool treats a target service as a black box and probes it from the outside, the same way a user or another service would. It does not require any access to the internals of what it is checking. You point it at a URL, server, or hostname and it performs a test, then reports whether the test passed and how long it took.

The tool supports several types of probes. HTTP and HTTPS probes check that a web address responds with the expected status code. TCP probes verify that a port on a server is accepting connections. DNS probes query a name server and check that it returns valid results. ICMP probes send ping-style packets to test basic connectivity. gRPC probes check services using that communication protocol.

Results are exposed in a format that Prometheus can collect and store. Each probe produces a set of measurements including whether the probe succeeded, how long the connection took to establish, how long the full request took, and other timing details. These measurements can then be used to set up alerts, for example to notify an on-call engineer when a website stops responding or when response times cross a threshold.

The exporter is typically deployed alongside a Prometheus server, which is configured to call the exporter at regular intervals with the targets to probe. Configuration is done through a YAML file that defines named probe modules with their settings. The exporter is written in Go, available as a prebuilt binary and as a Docker image, and is an official project under the Prometheus organization.