Matrix targets

A matrix strategy lets you fork a single target into multiple different variants, based on parameters that you specify. This works in a similar way to Matrix strategies for GitHub Actions. You can use this to reduce duplication in your Bake definition.

The matrix attribute is a map of parameter names to lists of values. Bake builds each possible combination of values as a separate target.

Each generated target must have a unique name. To specify how target names should resolve, use the name attribute.

The following example resolves the app target to app-foo and app-bar. It also uses the matrix value to define the target build stage.

target "app" {   name = "app-${tgt}"   matrix = {     tgt = ["foo", "bar"]   }   target = tgt }

$ docker buildx bake --print app [+] Building 0.0s (0/0) {   "group": {     "app": {       "targets": [         "app-foo",         "app-bar"       ]     },     "default": {       "targets": [         "app"       ]     }   },   "target": {     "app-bar": {       "context": ".",       "dockerfile": "Dockerfile",       "target": "bar"     },     "app-foo": {       "context": ".",       "dockerfile": "Dockerfile",       "target": "foo"     }   } } 

Multiple axes

You can specify multiple keys in your matrix to fork a target on multiple axes. When using multiple matrix keys, Bake builds every possible variant.

The following example builds four targets:

• app-foo-1-0
• app-foo-2-0
• app-bar-1-0
• app-bar-2-0

target "app" {   name = "app-${tgt}-${replace(version, ".", "-")}"   matrix = {     tgt = ["foo", "bar"]     version = ["1.0", "2.0"]   }   target = tgt   args = {     VERSION = version   } }

Multiple values per matrix target

If you want to differentiate the matrix on more than just a single value, you can use maps as matrix values. Bake creates a target for each map, and you can access the nested values using dot notation.

The following example builds two targets:

• app-foo-1-0
• app-bar-2-0

target "app" {   name = "app-${item.tgt}-${replace(item.version, ".", "-")}"   matrix = {     item = [       {         tgt = "foo"         version = "1.0"       },       {         tgt = "bar"         version = "2.0"       }     ]   }   target = item.tgt   args = {     VERSION = item.version   } }