Dynamic blackbox module (grafana#13)

* Added dynamic blackbox module

README.md

@@ -16,6 +16,7 @@ parameterize a configuration to create reusable pipelines.
 | ---- |  ----------- | ------------- | 
 | [OTLP to LGTM](./modules/otlp/otlp-to-lgtm/) | Module to ingest OTLP data and then send it to Loki, Mimir and Tempo stacks locally or in GrafanaCloud. | `>= v0.33`
 | [Grafana Agent Telemetry to LGTM](./modules/grafana-agent/telemetry-to-lgtm/) | Module to forward the Grafana Agent's own telemetry data to Loki, Mimir and Tempo stacks locally or in Grafana Cloud. | `>= v0.33`
+| [Grafana Agent Dynamic Blackbox Exporter](./modules/grafana-agent/dynamic-blackbox/) | Module to use blackbox exporter with dynamic targets. | `>= v0.35`
 | [Grafana Cloud Autoconfigure](./modules/grafana-cloud/autoconfigure/) | Module to automatically configure receivers for Grafana Cloud. | `>= v0.34`
 | [Host Filtering](./modules/host-filter/) | The host filtering module provides a Flow mode equivalent to static mode's host filtering functionality. | `>= v0.34`
 

modules/grafana-agent/dynamic-blackbox/README.md

@@ -0,0 +1,85 @@
+# Grafana Agent Dynamic Blackbox Exporter
+
+A module to add a dynamic target list to blackbox exporter.
+
+The `prometheus.exporter.blackbox` component expects a series of target blocks as part of its configuration and doesn't accept a list of targets from another component.
+
+This module allows a list of targets from another component to be used by blackbox exporter for scraping.
+
+## Agent Version
+
+`>= v0.35`
+
+## Module arguments
+
+The following arguments are supported when passing arguments to the module loader:
+
+| Name | Type | Description | Default | Required
+| ---- | ---- | ----------- | ------- | --------
+| `targets`  | `list(map(string))`   | List of targets for blackbox | | yes
+| `target_label` | `string` | Metric label the original target label will be added to | `"address"` | no
+| `config_file`     | `string` or `secret`  | 	blackbox_exporter configuration file path | | no
+| `config` | `secret`   | blackbox_exporter configuration as inline string | | no
+| `probe_timeout_offset`       | `duration`   | Offset in seconds to subtract from timeout when probing targets | `"0.5s"` | no
+
+The arguments `config` and `config_file` are mutually exclusive. If neither are specified, a default config is used.
+
+The `config_file` argument points to a YAML file defining which blackbox_exporter modules to use.
+The `config` argument must be a YAML document as string defining which blackbox_exporter modules to use.
+`config` is typically loaded by using the exports of another component. For example,
+
+- `local.file.LABEL.content`
+- `remote.http.LABEL.content`
+- `remote.s3.LABEL.content`
+
+See [blackbox_exporter]( https://github.com/prometheus/blackbox_exporter/blob/master/example.yml) for details on how to generate a config file.
+
+## Module exports
+
+The following fields are exported by the module:
+
+| Name | Type | Description
+| ---- | ---- | -----------
+| `targets` | `list(map(string))` | The targets that can be used to collect blackbox metrics.
+
+## Example
+
+```
+discovery.file "targets" {
+  files = ["targets.yml"]
+}
+
+module.git "blackbox" {
+    repository = "https://github.com/grafana/agent-modules.git"
+    revision   = "main"
+    path       = "modules/grafana-agent/dynamic-blackbox/module.river"
+
+  arguments {
+    config = "{ modules: { tcps: { prober: tcp, tcp: { tls: true, tls_config: { insecure_skip_verify: true } } } } }"
+    targets = discovery.file.targets.targets
+  }
+}
+
+prometheus.scrape "scrape" {
+  targets    = module.git.blackbox.exports.targets
+  forward_to = [ prometheus.remote_write.main.receiver ]
+}
+
+prometheus.remote_write "main" {
+  endpoint {
+    url = "http://url/to/push"
+  }
+}
+```
+
+Add a `__param_module` label in the targets.yml to select the blackbox module to use with a given target.
+
+```
+---
+- labels:
+    type: external
+    __param_module: tcps
+  targets:
+  - grafana.com:443
+  - prometheus.io:443
+```

modules/grafana-agent/dynamic-blackbox/module.river

@@ -0,0 +1,65 @@
+/********************************************
+ * ARGUMENTS
+ ********************************************/
+argument "targets" { }
+
+argument "target_label" {
+  optional = true
+  default = "address"
+}
+
+argument "config_file" {
+  optional = true 
+}
+
+argument "config" {
+  optional = true 
+}
+
+argument "probe_timeout_offset" {
+  optional = true
+}
+
+/********************************************
+ * EXPORTS
+ ********************************************/
+export "targets" {
+  value = discovery.relabel.default.output
+}
+
+/********************************************
+ * LOGIC
+ ********************************************/
+
+prometheus.exporter.blackbox "base" {
+  config_file	= argument.config_file.value
+  config = argument.config.value
+  probe_timeout_offset = argument.probe_timeout_offset.value
+  target "dummy" {
+    address = "dummy"
+  }
+}
+
+discovery.relabel "default" {
+  targets = argument.targets.value
+
+  rule {
+    source_labels = ["__address__"]
+    target_label  = "__param_target"
+  }
+
+  rule {
+    source_labels = ["__address__"]
+    target_label  = argument.target_label.value
+  }
+
+  rule {
+    target_label = "__address__"
+    replacement = prometheus.exporter.blackbox.base.targets[0].__address__
+  }
+
+  rule {
+    target_label = "__metrics_path__"
+    replacement  = prometheus.exporter.blackbox.base.targets[0].__metrics_path__
+  }
+}