chore: Use build tags to select plugins (#11654)

Makefile

@@ -125,7 +125,7 @@ docs: build_tools embed_readme_inputs embed_readme_outputs embed_readme_processo
 
 .PHONY: build
 build:
-	go build -ldflags "$(LDFLAGS)" ./cmd/telegraf
+	go build -tags "$(BUILDTAGS)" -ldflags "$(LDFLAGS)" ./cmd/telegraf
 
 .PHONY: telegraf
 telegraf: build

docs/AGGREGATORS.md

@@ -7,8 +7,10 @@ This section is for developers who want to create a new aggregator plugin.
 * A aggregator must conform to the [telegraf.Aggregator][] interface.
 * Aggregators should call `aggregators.Add` in their `init` function to
   register themselves.  See below for a quick example.
-* To be available within Telegraf itself, plugins must add themselves to the
-  `github.com/influxdata/telegraf/plugins/aggregators/all/all.go` file.
+* To be available within Telegraf itself, plugins must register themselves
+  using a file in `github.com/influxdata/telegraf/plugins/aggregators/all`
+  named according to the plugin name. Make sure your also add build-tags to
+  conditionally build the plugin.
 * Each plugin requires a file called `sample.conf` containing the sample configuration
   for the plugin in TOML format.
   Please consult the [Sample Config][] page for the latest style guidelines.
@@ -22,6 +24,8 @@ This section is for developers who want to create a new aggregator plugin.
 
 ### Aggregator Plugin Example
 
+Content of your plugin file e.g. `min.go`
+
 ```go
 //go:generate ../../../tools/readme_config_includer/generator
 package min
@@ -122,3 +126,21 @@ func init() {
     })
 }
 ```
+
+Registration of the plugin on `plugins/aggregators/all/min.go`:
+
+```go
+//go:build !custom || aggregators || aggregators.min
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/min" // register plugin
+
+```
+
+The _build-tags_ in the first line allow to selectively include/exclude your
+plugin when customizing Telegraf.
+
+[Sample Config]: https://github.com/influxdata/telegraf/blob/master/docs/developers/SAMPLE_CONFIG.md
+[Code Style]: https://github.com/influxdata/telegraf/blob/master/docs/developers/CODE_STYLE.md
+[telegraf.Aggregator]: https://godoc.org/github.com/influxdata/telegraf#Aggregator

docs/CUSTOMIZATION.md

@@ -0,0 +1,45 @@
+# Customization
+
+You can build customized versions of Telegraf with a specific plugin set
+using [build-tags](https://pkg.go.dev/cmd/go#hdr-Build_constraints).
+The plugins can be selected either category-wise, i.e. `inputs`, `outputs`,
+`processors`, `aggregators` and `parsers` or individually, e.g. `inputs.modbus`
+or `outputs.influxdb`.
+
+Usually the build tags correspond to the plugin names used in the Telegraf
+configuration. To be sure, check the files in the corresponding
+`plugin/<category>/all` directory. Make sure to include all parsers you intend
+to use.
+
+__Note:__ You _always_ need to include the `custom` tag when customizing the
+build as otherwise _all_ plugins will be selected regardless of other tags.
+
+## Via make
+
+When using the project's makefile, the build can be customized via the
+`BUILDTAGS` environment variable containing a __space-separated__ list of the
+selected plugins (or categories) __and__ the `custom` tag.
+
+For example
+
+```shell
+BUILDTAGS="custom inputs outputs.influxdb_v2 parsers.json" make
+```
+
+will build a customized Telegraf including _all_ `inputs`, the InfluxDB v2
+`output` and the `json` parser.
+
+## Via `go build`
+
+If you wish to build Telegraf using native go tools, you can use the `go build`
+command with the `-tags` option. Specify  a __space-separated__ list of the
+selected plugins (or categories) __and__ the `custom` tag as argument.
+
+For example
+
+```shell
+go build -tags "custom inputs outputs.influxdb_v2 parsers.json" ./cmd/telegraf
+```
+
+will build a customized Telegraf including _all_ `inputs`, the InfluxDB v2
+`output` and the `json` parser.

docs/INPUTS.md

@@ -13,8 +13,10 @@ and submit new inputs.
 - A plugin must conform to the [telegraf.Input][] interface.
 - Input Plugins should call `inputs.Add` in their `init` function to register
   themselves.  See below for a quick example.
-- Input Plugins must be added to the
-  `github.com/influxdata/telegraf/plugins/inputs/all/all.go` file.
+- To be available within Telegraf itself, plugins must register themselves
+  using a file in `github.com/influxdata/telegraf/plugins/inputs/all` named
+  according to the plugin name. Make sure your also add build-tags to
+  conditionally build the plugin.
 - Each plugin requires a file called `sample.conf` containing the sample
   configuration  for the plugin in TOML format.
   Please consult the [Sample Config][] page for the latest style guidelines.
@@ -27,6 +29,8 @@ current host.
 
 ## Input Plugin Example
 
+Content of your plugin file e.g. `simple.go`
+
 ```go
 //go:generate ../../../tools/readme_config_includer/generator
 package simple
@@ -71,11 +75,25 @@ func init() {
 }
 ```
 
+Registration of the plugin on `plugins/inputs/all/simple.go`:
+
+```go
+//go:build !custom || inputs || inputs.simple
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/inputs/simple" // register plugin
+
+```
+
+The _build-tags_ in the first line allow to selectively include/exclude your
+plugin when customizing Telegraf.
+
 ### Development
 
 - Run `make static` followed by `make plugin-[pluginName]` to spin up a docker
   dev environment using docker-compose.
-- ***[Optional]*** When developing a plugin, add a `dev` directory with a
+- __[Optional]__ When developing a plugin, add a `dev` directory with a
   `docker-compose.yml` and `telegraf.conf` as well as any other supporting
   files, where sensible.
 

docs/OUTPUTS.md

@@ -9,8 +9,10 @@ similar constructs.
 - An output must conform to the [telegraf.Output][] interface.
 - Outputs should call `outputs.Add` in their `init` function to register
   themselves.  See below for a quick example.
-- To be available within Telegraf itself, plugins must add themselves to the
-  `github.com/influxdata/telegraf/plugins/outputs/all/all.go` file.
+- To be available within Telegraf itself, plugins must register themselves
+  using a file in `github.com/influxdata/telegraf/plugins/outputs/all` named
+  according to the plugin name. Make sure your also add build-tags to
+  conditionally build the plugin.
 - Each plugin requires a file called `sample.conf` containing the sample
   configuration  for the plugin in TOML format.
   Please consult the [Sample Config][] page for the latest style guidelines.
@@ -20,6 +22,8 @@ similar constructs.
 
 ## Output Plugin Example
 
+Content of your plugin file e.g. `simpleoutput.go`
+
 ```go
 //go:generate ../../../tools/readme_config_includer/generator
 package simpleoutput
@@ -75,9 +79,22 @@ func (s *Simple) Write(metrics []telegraf.Metric) error {
 func init() {
     outputs.Add("simpleoutput", func() telegraf.Output { return &Simple{} })
 }
+```
+
+Registration of the plugin on `plugins/outputs/all/simpleoutput.go`:
+
+```go
+//go:build !custom || outputs || outputs.simpleoutput
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/outputs/simpleoutput" // register plugin
 
 ```
 
+The _build-tags_ in the first line allow to selectively include/exclude your
+plugin when customizing Telegraf.
+
 ## Data Formats
 
 Some output plugins, such as the [file][] plugin, can write in any supported

docs/PROCESSORS.md

@@ -7,8 +7,10 @@ This section is for developers who want to create a new processor plugin.
 * A processor must conform to the [telegraf.Processor][] interface.
 * Processors should call `processors.Add` in their `init` function to register
   themselves.  See below for a quick example.
-* To be available within Telegraf itself, plugins must add themselves to the
-  `github.com/influxdata/telegraf/plugins/processors/all/all.go` file.
+* To be available within Telegraf itself, plugins must register themselves
+  using a file in `github.com/influxdata/telegraf/plugins/processors/all`
+  named according to the plugin name. Make sure your also add build-tags to
+  conditionally build the plugin.
 * Each plugin requires a file called `sample.conf` containing the sample
   configuration  for the plugin in TOML format.
   Please consult the [Sample Config][] page for the latest style guidelines.
@@ -18,6 +20,8 @@ This section is for developers who want to create a new processor plugin.
 
 ## Processor Plugin Example
 
+Content of your plugin file e.g. `printer.go`
+
 ```go
 //go:generate ../../../tools/readme_config_includer/generator
 package printer
@@ -63,6 +67,19 @@ func init() {
 }
 ```
 
+Registration of the plugin on `plugins/processors/all/printer.go`:
+
+```go
+//go:build !custom || processors || processors.printer
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/processors/printer" // register plugin
+```
+
+The _build-tags_ in the first line allow to selectively include/exclude your
+plugin when customizing Telegraf.
+
 ## Streaming Processors
 
 Streaming processors are a new processor type available to you. They are

docs/README.md

@@ -11,7 +11,7 @@
   - [Windows Service][winsvc]
   - [FAQ][faq]
 - Developer Builds
-  - [Nightlies](nightlies)
+  - [Nightlies][nightlies]
 
 [conf]: /docs/CONFIGURATION.md
 [metrics]: /docs/METRICS.md

plugins/aggregators/all/all.go

@@ -1,14 +1 @@
 package all
-
-import (
-	//Blank imports for plugins to register themselves
-	_ "github.com/influxdata/telegraf/plugins/aggregators/basicstats"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/derivative"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/final"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/histogram"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/merge"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/minmax"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/quantile"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/starlark"
-	_ "github.com/influxdata/telegraf/plugins/aggregators/valuecounter"
-)

plugins/aggregators/all/basicstats.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.basicstats
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/basicstats" // register plugin

plugins/aggregators/all/derivative.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.derivative
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/derivative" // register plugin

plugins/aggregators/all/final.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.final
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/final" // register plugin

plugins/aggregators/all/histogram.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.histogram
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/histogram" // register plugin

plugins/aggregators/all/merge.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.merge
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/merge" // register plugin

plugins/aggregators/all/minmax.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.minmax
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/minmax" // register plugin

plugins/aggregators/all/quantile.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.quantile
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/quantile" // register plugin

plugins/aggregators/all/starlark.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.starlark
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/starlark" // register plugin

plugins/aggregators/all/valuecounter.go

@@ -0,0 +1,5 @@
+//go:build !custom || aggregators || aggregators.valuecounter
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/valuecounter" // register plugin

plugins/inputs/all/activemq.go

@@ -0,0 +1,5 @@
+//go:build !custom || inputs || inputs.activemq
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/inputs/activemq" // register plugin

plugins/inputs/all/aerospike.go

@@ -0,0 +1,5 @@
+//go:build !custom || inputs || inputs.aerospike
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/inputs/aerospike" // register plugin

plugins/inputs/all/aliyuncms.go

@@ -0,0 +1,5 @@
+//go:build !custom || inputs || inputs.aliyuncms
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/inputs/aliyuncms" // register plugin