feat: add option to disable prepared statements for PostgreSQL (#9710)

plugins/inputs/postgresql/README.md

@@ -62,6 +62,39 @@ host=localhost user=pgotest dbname=app_production sslmode=require sslkey=/etc/te
 
 ```toml
 [[inputs.postgresql]]
-  address = "postgres://telegraf@localhost/someDB"
-  ignored_databases = ["template0", "template1"]
+  ## specify address via a url matching:
+  ##   postgres://[pqgotest[:password]]@localhost[/dbname]?sslmode=[disable|verify-ca|verify-full]
+  ## or a simple string:
+  ##   host=localhost user=pqgotest password=... sslmode=... dbname=app_production
+  ##
+  ## All connection parameters are optional.
+  ##
+  ## Without the dbname parameter, the driver will default to a database
+  ## with the same name as the user. This dbname is just for instantiating a
+  ## connection with the server and doesn't restrict the databases we are trying
+  ## to grab metrics for.
+  ##
+  address = "host=localhost user=postgres sslmode=disable"
+  ## A custom name for the database that will be used as the "server" tag in the
+  ## measurement output. If not specified, a default one generated from
+  ## the connection address is used.
+  # outputaddress = "db01"
+
+  ## connection configuration.
+  ## maxlifetime - specify the maximum lifetime of a connection.
+  ## default is forever (0s)
+  # max_lifetime = "0s"
+
+  ## A  list of databases to explicitly ignore.  If not specified, metrics for all
+  ## databases are gathered.  Do NOT use with the 'databases' option.
+  # ignored_databases = ["postgres", "template0", "template1"]
+
+  ## A list of databases to pull metrics about. If not specified, metrics for all
+  ## databases are gathered.  Do NOT use with the 'ignored_databases' option.
+  # databases = ["app_production", "testing"]
+
+  ## Whether to use prepared statements when connecting to the database.
+  ## This should be set to false when connecting through a PgBouncer instance
+  ## with pool_mode set to transaction.
+  prepared_statements = true
 ```

plugins/inputs/postgresql/postgresql.go

@@ -15,8 +15,9 @@ import (
 
 type Postgresql struct {
 	Service
-	Databases        []string
-	IgnoredDatabases []string
+	Databases          []string `toml:"databases"`
+	IgnoredDatabases   []string `toml:"ignored_databases"`
+	PreparedStatements bool     `toml:"prepared_statements"`
 }
 
 var ignoredColumns = map[string]bool{"stats_reset": true}
@@ -53,6 +54,11 @@ var sampleConfig = `
   ## A list of databases to pull metrics about. If not specified, metrics for all
   ## databases are gathered.  Do NOT use with the 'ignored_databases' option.
   # databases = ["app_production", "testing"]
+
+  ## Whether to use prepared statements when connecting to the database.
+  ## This should be set to false when connecting through a PgBouncer instance
+  ## with pool_mode set to transaction.
+  # prepared_statements = true
 `
 
 func (p *Postgresql) SampleConfig() string {
@@ -67,6 +73,11 @@ func (p *Postgresql) IgnoredColumns() map[string]bool {
 	return ignoredColumns
 }
 
+func (p *Postgresql) Init() error {
+	p.Service.IsPgBouncer = !p.PreparedStatements
+	return nil
+}
+
 func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 	var (
 		err     error
@@ -198,8 +209,8 @@ func init() {
 				MaxIdle:     1,
 				MaxOpen:     1,
 				MaxLifetime: config.Duration(0),
-				IsPgBouncer: false,
 			},
+			PreparedStatements: true,
 		}
 	})
 }

plugins/inputs/postgresql/service.go

@@ -94,7 +94,7 @@ type Service struct {
 	MaxOpen       int
 	MaxLifetime   config.Duration
 	DB            *sql.DB
-	IsPgBouncer   bool
+	IsPgBouncer   bool `toml:"-"`
 }
 
 var socketRegexp = regexp.MustCompile(`/\.s\.PGSQL\.\d+$`)

plugins/inputs/postgresql_extensible/README.md

@@ -28,7 +28,12 @@ The example below has two queries are specified, with the following parameters:
   # A list of databases to pull metrics about. If not specified, metrics for all
   # databases are gathered.
   # databases = ["app_production", "testing"]
-  #
+
+  ## Whether to use prepared statements when connecting to the database.
+  ## This should be set to false when connecting through a PgBouncer instance
+  ## with pool_mode set to transaction.
+  prepared_statements = true
+
   # Define the toml config where the sql queries are stored
   # New queries can be added, if the withdbname is set to true and there is no
   # databases defined in the 'databases field', the sql query is ended by a 'is

plugins/inputs/postgresql_extensible/postgresql_extensible.go

@@ -18,11 +18,12 @@ import (
 
 type Postgresql struct {
 	postgresql.Service
-	Databases      []string
-	AdditionalTags []string
-	Timestamp      string
-	Query          query
-	Debug          bool
+	Databases          []string
+	AdditionalTags     []string
+	Timestamp          string
+	Query              query
+	Debug              bool
+	PreparedStatements bool `toml:"prepared_statements"`
 
 	Log telegraf.Logger
 }
@@ -59,6 +60,11 @@ var sampleConfig = `
   ## default is forever (0s)
   max_lifetime = "0s"
 
+  ## Whether to use prepared statements when connecting to the database.
+  ## This should be set to false when connecting through a PgBouncer instance
+  ## with pool_mode set to transaction.
+  # prepared_statements = true
+
   ## A list of databases to pull metrics about. If not specified, metrics for all
   ## databases are gathered.
   ## databases = ["app_production", "testing"]
@@ -125,6 +131,7 @@ func (p *Postgresql) Init() error {
 			}
 		}
 	}
+	p.Service.IsPgBouncer = !p.PreparedStatements
 	return nil
 }
 
@@ -348,6 +355,7 @@ func init() {
 				MaxLifetime: config.Duration(0),
 				IsPgBouncer: false,
 			},
+			PreparedStatements: true,
 		}
 	})
 }