Custom Config Values (#117)

* Fix #94: Support custom start parameters.

Add a StartParameters config taking configuration settings.

These run-time configuration parameters override those set in the
default postgres.conf, and are passed to the postgres process via the
options flag of pg_ctl.

* Ensure we do run tests for non apple silicon.

---------

Co-authored-by: Josh Giles <jgiles@paxos.com>

README.md

@@ -87,6 +87,7 @@ RuntimePath("/tmp").
 BinaryRepositoryURL("https://repo.local/central.proxy").	
 Port(9876).
 StartTimeout(45 * time.Second).
+StartParameters(map[string]string{"max_connections": "200"}).	
 Logger(logger))
 err := postgres.Start()
 

config.go

@@ -18,6 +18,7 @@ type Config struct {
 	dataPath            string
 	binariesPath        string
 	locale              string
+	startParameters     map[string]string
 	binaryRepositoryURL string
 	startTimeout        time.Duration
 	logger              io.Writer
@@ -101,6 +102,15 @@ func (c Config) Locale(locale string) Config {
 	return c
 }
 
+// StartParameters sets run-time parameters when starting Postgres (passed to Postgres via "-c").
+//
+// These parameters can be used to override the default configuration values in postgres.conf such
+// as max_connections=100. See https://www.postgresql.org/docs/current/runtime-config.html
+func (c Config) StartParameters(parameters map[string]string) Config {
+	c.startParameters = parameters
+	return c
+}
+
 // StartTimeout sets the max timeout that will be used when starting the Postgres process and creating the initial database.
 func (c Config) StartTimeout(timeout time.Duration) Config {
 	c.startTimeout = timeout

embedded_postgres.go

@@ -193,11 +193,20 @@ func (ep *EmbeddedPostgres) Stop() error {
 	return nil
 }
 
+func encodeOptions(port uint32, parameters map[string]string) string {
+	options := []string{fmt.Sprintf("-p %d", port)}
+	for k, v := range parameters {
+		// Single-quote parameter values - they may have spaces.
+		options = append(options, fmt.Sprintf("-c %s='%s'", k, v))
+	}
+	return strings.Join(options, " ")
+}
+
 func startPostgres(ep *EmbeddedPostgres) error {
 	postgresBinary := filepath.Join(ep.config.binariesPath, "bin/pg_ctl")
 	postgresProcess := exec.Command(postgresBinary, "start", "-w",
 		"-D", ep.config.dataPath,
-		"-o", fmt.Sprintf(`"-p %d"`, ep.config.port))
+		"-o", encodeOptions(ep.config.port, ep.config.startParameters))
 	postgresProcess.Stdout = ep.syncedLogger.file
 	postgresProcess.Stderr = ep.syncedLogger.file
 

embedded_postgres_test.go

@@ -233,7 +233,7 @@ func Test_ErrorWhenCannotStartPostgresProcess(t *testing.T) {
 
 	err = database.Start()
 
-	assert.EqualError(t, err, fmt.Sprintf("could not start postgres using %s/bin/pg_ctl start -w -D %s/data -o \"-p 5432\":\nah it did not work", extractPath, extractPath))
+	assert.EqualError(t, err, fmt.Sprintf("could not start postgres using %s/bin/pg_ctl start -w -D %s/data -o -p 5432:\nah it did not work", extractPath, extractPath))
 }
 
 func Test_CustomConfig(t *testing.T) {
@@ -416,6 +416,40 @@ func Test_ConcurrentStart(t *testing.T) {
 	wg.Wait()
 }
 
+func Test_CustomStartParameters(t *testing.T) {
+	database := NewDatabase(DefaultConfig().StartParameters(map[string]string{
+		"max_connections": "101",
+		"shared_buffers":  "16 MB", // Ensure a parameter with spaces encodes correctly.
+	}))
+	if err := database.Start(); err != nil {
+		shutdownDBAndFail(t, err, database)
+	}
+
+	db, err := sql.Open("postgres", "host=localhost port=5432 user=postgres password=postgres dbname=postgres sslmode=disable")
+	if err != nil {
+		shutdownDBAndFail(t, err, database)
+	}
+
+	if err := db.Ping(); err != nil {
+		shutdownDBAndFail(t, err, database)
+	}
+
+	row := db.QueryRow("SHOW max_connections")
+	var res string
+	if err := row.Scan(&res); err != nil {
+		shutdownDBAndFail(t, err, database)
+	}
+	assert.Equal(t, "101", res)
+
+	if err := db.Close(); err != nil {
+		shutdownDBAndFail(t, err, database)
+	}
+
+	if err := database.Stop(); err != nil {
+		shutdownDBAndFail(t, err, database)
+	}
+}
+
 func Test_CanStartAndStopTwice(t *testing.T) {
 	database := NewDatabase()
 

platform-test/platform_test.go

@@ -18,7 +18,9 @@ func Test_AllMajorVersions(t *testing.T) {
 		embeddedpostgres.V14,
 	}
 
-	if runtime.GOOS != "darwin" && runtime.GOARCH == "arm64" {
+	isLikelyAppleSilicon := runtime.GOOS == "darwin" && runtime.GOARCH == "arm64"
+
+	if !isLikelyAppleSilicon {
 		allVersions = append(allVersions,
 			embeddedpostgres.V13,
 			embeddedpostgres.V12,