feat: allow use of mamba solver in place of conda's default solver

This can be enabled through the use of the BP_CONDA_SOLVER environment variable.
The use of the mamba solver offers a welcome speedup for the resolution of
conda environments.

Author: sgaist

build.go

@@ -1,13 +1,15 @@
 package miniconda
 
 import (
+	"os"
 	"path/filepath"
 	"time"
 
 	"github.com/paketo-buildpacks/packit/v2"
 	"github.com/paketo-buildpacks/packit/v2/cargo"
 	"github.com/paketo-buildpacks/packit/v2/chronos"
 	"github.com/paketo-buildpacks/packit/v2/draft"
+	"github.com/paketo-buildpacks/packit/v2/pexec"
 	"github.com/paketo-buildpacks/packit/v2/postal"
 	"github.com/paketo-buildpacks/packit/v2/sbom"
 	"github.com/paketo-buildpacks/packit/v2/scribe"
@@ -34,6 +36,14 @@ type SBOMGenerator interface {
 	GenerateFromDependency(dependency postal.Dependency, dir string) (sbom.SBOM, error)
 }
 
+func GetEnvOrDefault(key, defaultValue string) string {
+	value, exists := os.LookupEnv(key)
+	if !exists {
+		return defaultValue
+	}
+	return value
+}
+
 // Build will return a packit.BuildFunc that will be invoked during the build
 // phase of the buildpack lifecycle.
 //
@@ -137,6 +147,39 @@ func Build(
 		logger.Action("Completed in %s", duration.Round(time.Millisecond))
 		logger.Break()
 
+		solver := GetEnvOrDefault("BP_CONDA_SOLVER", "conda")
+
+		if solver == "mamba" {
+			logger.Subprocess("Installing mamba solver")
+
+			conda := pexec.NewExecutable(condaLayer.Path + "/bin/conda")
+			duration, err = clock.Measure(func() error {
+				return conda.Execute(pexec.Execution{
+					Args: []string{"install", "-n", "base", "conda-libmamba-solver", "-y"},
+				})
+			})
+			if err != nil {
+				return packit.BuildResult{}, err
+			}
+
+			logger.Action("Solver completed in %s", duration.Round(time.Millisecond))
+			logger.Break()
+
+			logger.Subprocess("Configuring mamba solver")
+			duration, err = clock.Measure(func() error {
+				return conda.Execute(pexec.Execution{
+					Args: []string{"config", "--set", "solver", "libmamba"},
+				})
+			})
+			if err != nil {
+				return packit.BuildResult{}, err
+			}
+
+			logger.Action("Configuration completed in %s", duration.Round(time.Millisecond))
+			logger.Break()
+
+		}
+
 		condaLayer.Metadata = map[string]interface{}{
 			DepKey: dependencyChecksum,
 		}

integration/logging_test.go

@@ -72,5 +72,35 @@ func testLogging(t *testing.T, context spec.G, it spec.S) {
 				MatchRegexp(`      Completed in ([0-9]*(\.[0-9]*)?[a-z]+)+`),
 			))
 		})
+
+		it("logs helpful information to the user with mamba installation", func() {
+			var (
+				logs fmt.Stringer
+				err  error
+			)
+
+			image, logs, err = pack.WithNoColor().Build.
+				WithEnv(map[string]string{"BP_CONDA_SOLVER": "mamba"}).
+				WithPullPolicy("never").
+				WithBuildpacks(
+					settings.Buildpacks.Miniconda.Online,
+					settings.Buildpacks.BuildPlan.Online,
+				).
+				Execute(name, source)
+			Expect(err).ToNot(HaveOccurred(), logs.String)
+
+			Expect(logs).To(ContainLines(
+				MatchRegexp(fmt.Sprintf(`%s \d+\.\d+\.\d+`, settings.Buildpack.Name)),
+				"  Executing build process",
+				MatchRegexp(`    Installing Miniconda \d+\.\d+\.\d+`),
+				MatchRegexp(`      Completed in ([0-9]*(\.[0-9]*)?[a-z]+)+`),
+				"",
+				"    Installing mamba solver",
+				MatchRegexp(`      Solver completed in ([0-9]*(\.[0-9]*)?[a-z]+)+`),
+				"",
+				"    Configuring mamba solver",
+				MatchRegexp(`      Configuration completed in ([0-9]*(\.[0-9]*)?[a-z]+)+`),
+			))
+		})
 	})
 }