feat(config): Add env and file support for database max connections

CHANGELOG.md

@@ -6,6 +6,9 @@ Canonical reference for changes, improvements, and bugfixes for Boundary.
 
 ### New and Improved
 
+* config: The `max_open_connections` field for the database field in controllers now supports being set
+  from environment variables or a file on disk
+  ([PR](https://github.com/hashicorp/boundary/pull/1776))
 * config: The `execution_dir` field for plugins now supports being set from environment variables
   or a file on disk.([PR](https://github.com/hashicorp/boundary/pull/1772))
 * config: Add support for reading worker controllers off of environment

internal/cmd/config/config.go

@@ -10,6 +10,7 @@ import (
 	"io"
 	"io/ioutil"
 	"reflect"
+	"strconv"
 	"strings"
 	"time"
 
@@ -198,9 +199,10 @@ func initNameIfEmpty(name *string) error {
 }
 
 type Database struct {
-	Url                string `hcl:"url"`
-	MigrationUrl       string `hcl:"migration_url"`
-	MaxOpenConnections int    `hcl:"max_open_connections"`
+	Url                   string      `hcl:"url"`
+	MigrationUrl          string      `hcl:"migration_url"`
+	MaxOpenConnections    int         `hcl:"-"`
+	MaxOpenConnectionsRaw interface{} `hcl:"max_open_connections"`
 }
 
 type Plugins struct {
@@ -338,6 +340,27 @@ func Parse(d string) (*Config, error) {
 			}
 			result.Controller.AuthTokenTimeToStaleDuration = t
 		}
+
+		if result.Controller.Database != nil {
+			if result.Controller.Database.MaxOpenConnectionsRaw != nil {
+				switch t := result.Controller.Database.MaxOpenConnectionsRaw.(type) {
+				case string:
+					maxOpenConnectionsString, err := parseutil.ParsePath(t)
+					if err != nil {
+						return nil, fmt.Errorf("Error parsing database max open connections: %w", err)
+					}
+					result.Controller.Database.MaxOpenConnections, err = strconv.Atoi(maxOpenConnectionsString)
+					if err != nil {
+						return nil, fmt.Errorf("Database max open connections value is not an int: %w", err)
+					}
+				case int:
+					result.Controller.Database.MaxOpenConnections = t
+				default:
+					return nil, fmt.Errorf("Database max open connections: unsupported type %q",
+						reflect.TypeOf(t).String())
+				}
+			}
+		}
 	}
 
 	// Parse worker tags

internal/cmd/config/config_test.go

@@ -1052,3 +1052,96 @@ func TestPluginExecutionDir(t *testing.T) {
 		})
 	}
 }
+
+func TestDatabaseMaxConnections(t *testing.T) {
+	tests := []struct {
+		name                  string
+		in                    string
+		envMaxOpenConnections string
+		expMaxOpenConnections int
+		expErr                bool
+		expErrStr             string
+	}{
+		{
+			name: "Valid integer value",
+			in: `
+			controller {
+				name = "example-controller"
+				database {
+					max_open_connections = 5
+			  	}
+			}`,
+			expMaxOpenConnections: 5,
+			expErr:                false,
+		},
+		{
+			name: "Invalid value string",
+			in: `
+			controller {
+				name = "example-controller"
+				database {
+					max_open_connections = "string bad"
+				}
+			}`,
+			expErr: true,
+			expErrStr: "Database max open connections value is not an int: " +
+				"strconv.Atoi: parsing \"string bad\": invalid syntax",
+		},
+		{
+			name: "Invalid value type",
+			in: `
+			controller {
+				name = "example-controller"
+				database {
+					max_open_connections = false
+				}
+			}`,
+			expErr:    true,
+			expErrStr: "Database max open connections: unsupported type \"bool\"",
+		},
+		{
+			name: "Valid env var",
+			in: `
+			controller {
+				name = "example-controller"
+				database {
+					max_open_connections = "env://ENV_MAX_CONN"
+			  	}
+			}`,
+			expMaxOpenConnections: 8,
+			envMaxOpenConnections: "8",
+			expErr:                false,
+		},
+		{
+			name: "Invalid env var",
+			in: `
+			controller {
+				name = "example-controller"
+				database {
+					max_open_connections = "env://ENV_MAX_CONN"
+			  	}
+			}`,
+			envMaxOpenConnections: "bogus value",
+			expErr:                true,
+			expErrStr: "Database max open connections value is not an int: " +
+				"strconv.Atoi: parsing \"bogus value\": invalid syntax",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Setenv("ENV_MAX_CONN", tt.envMaxOpenConnections)
+			c, err := Parse(tt.in)
+			if tt.expErr {
+				require.EqualError(t, err, tt.expErrStr)
+				require.Nil(t, c)
+				return
+			}
+
+			require.NoError(t, err)
+			require.NotNil(t, c)
+			require.NotNil(t, c.Controller)
+			require.NotNil(t, c.Controller.Database)
+			require.Equal(t, tt.expMaxOpenConnections, c.Controller.Database.MaxOpenConnections)
+		})
+	}
+}

website/content/docs/configuration/controller.mdx

@@ -41,7 +41,9 @@ description will be read.
     connections that can be opened by the controller.
     The minimum number of connections required is 5.
     Setting this value to 0 will allow the controller to open as many
-    connections as needed.
+    connections as needed. This value can be a string representing the max number of connections, can refer to a file
+    on disk (file://) from which the number of connections will be read; or an env var (env://) from which the
+    number of connections will be read.
 
   Either URL can refer to a file on disk (file://) from which a URL will be read; an env
   var (env://) from which the URL will be read; or a direct database URL (postgres://).