feat: Add common expression language metric filtering (#13144)

config/config.go

@@ -1386,6 +1386,8 @@ func (c *Config) buildFilter(tbl *ast.Table) (models.Filter, error) {
 	c.getFieldStringSlice(tbl, "tagexclude", &f.TagExclude)
 	c.getFieldStringSlice(tbl, "taginclude", &f.TagInclude)
 
+	c.getFieldString(tbl, "metricpass", &f.MetricPass)
+
 	if c.hasErrs() {
 		return f, c.firstErr()
 	}
@@ -1536,7 +1538,7 @@ func (c *Config) missingTomlField(_ reflect.Type, key string) error {
 		"grace",
 		"interval",
 		"lvm", // What is this used for?
-		"metric_batch_size", "metric_buffer_limit",
+		"metric_batch_size", "metric_buffer_limit", "metricpass",
 		"name_override", "name_prefix", "name_suffix", "namedrop", "namepass",
 		"order",
 		"pass", "period", "precision",

config/config_test.go

@@ -21,6 +21,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/metric"
 	"github.com/influxdata/telegraf/models"
 	"github.com/influxdata/telegraf/persister"
 	"github.com/influxdata/telegraf/plugins/common/tls"
@@ -32,6 +33,7 @@ import (
 	"github.com/influxdata/telegraf/plugins/processors"
 	"github.com/influxdata/telegraf/plugins/serializers"
 	_ "github.com/influxdata/telegraf/plugins/serializers/all" // Blank import to have all serializers for testing
+	"github.com/influxdata/telegraf/testutil"
 )
 
 func TestReadBinaryFile(t *testing.T) {
@@ -514,6 +516,66 @@ func TestConfig_URLLikeFileName(t *testing.T) {
 	}
 }
 
+func TestConfig_Filtering(t *testing.T) {
+	c := NewConfig()
+	require.NoError(t, c.LoadAll("./testdata/filter_metricpass.toml"))
+	require.Len(t, c.Processors, 1)
+
+	in := []telegraf.Metric{
+		metric.New(
+			"machine",
+			map[string]string{"state": "on"},
+			map[string]interface{}{"value": 42.0},
+			time.Date(2023, time.April, 23, 01, 15, 30, 0, time.UTC),
+		),
+		metric.New(
+			"machine",
+			map[string]string{"state": "off"},
+			map[string]interface{}{"value": 23.0},
+			time.Date(2023, time.April, 23, 23, 59, 01, 0, time.UTC),
+		),
+		metric.New(
+			"temperature",
+			map[string]string{},
+			map[string]interface{}{"value": 23.5},
+			time.Date(2023, time.April, 24, 02, 15, 30, 0, time.UTC),
+		),
+	}
+	expected := []telegraf.Metric{
+		metric.New(
+			"machine",
+			map[string]string{
+				"state":     "on",
+				"processed": "yes",
+			},
+			map[string]interface{}{"value": 42.0},
+			time.Date(2023, time.April, 23, 01, 15, 30, 0, time.UTC),
+		),
+		metric.New(
+			"machine",
+			map[string]string{"state": "off"},
+			map[string]interface{}{"value": 23.0},
+			time.Date(2023, time.April, 23, 23, 59, 01, 0, time.UTC),
+		),
+		metric.New(
+			"temperature",
+			map[string]string{
+				"processed": "yes",
+			},
+			map[string]interface{}{"value": 23.5},
+			time.Date(2023, time.April, 24, 02, 15, 30, 0, time.UTC),
+		),
+	}
+
+	plugin := c.Processors[0]
+	var acc testutil.Accumulator
+	for _, m := range in {
+		require.NoError(t, plugin.Add(m, &acc))
+	}
+	actual := acc.GetTelegrafMetrics()
+	testutil.RequireMetricsEqual(t, expected, actual, testutil.SortMetrics())
+}
+
 func TestConfig_SerializerInterfaceNewFormat(t *testing.T) {
 	formats := []string{
 		"carbon2",
@@ -1434,11 +1496,13 @@ func (m *MockupProcessorPlugin) Stop() {
 func (m *MockupProcessorPlugin) SampleConfig() string {
 	return "Mockup test processor plugin with parser"
 }
-func (m *MockupProcessorPlugin) Apply(_ ...telegraf.Metric) []telegraf.Metric {
+func (m *MockupProcessorPlugin) Apply(in ...telegraf.Metric) []telegraf.Metric {
-	return nil
+	out := make([]telegraf.Metric, 0, len(in))
-}
+	for _, m := range in {
-func (m *MockupProcessorPlugin) Add(_ telegraf.Metric, _ telegraf.Accumulator) error {
+		m.AddTag("processed", "yes")
-	return nil
+		out = append(out, m)
+	}
+	return out
 }
 func (m *MockupProcessorPlugin) GetState() interface{} {
 	return m.state

config/testdata/filter_metricpass.toml

@@ -0,0 +1,2 @@
+[[processors.processor]]
+  metricpass = '("state" in tags and tags.state == "on") or time > timestamp("2023-04-24T00:00:00Z")'

docs/CONFIGURATION.md

@@ -595,11 +595,11 @@ excluded from a Processor or Aggregator plugin, it is skips the plugin and is
 sent onwards to the next stage of processing.
 
 - **namepass**:
-An array of [glob pattern][] strings.  Only metrics whose measurement name matches
+An array of [glob pattern][] strings. Only metrics whose measurement name
-a pattern in this list are emitted.
+matches a pattern in this list are emitted.
 
 - **namedrop**:
-The inverse of `namepass`.  If a match is found the metric is discarded. This
+The inverse of `namepass`. If a match is found the metric is discarded. This
 is tested on metrics after they have passed the `namepass` test.
 
 - **tagpass**:
@@ -620,6 +620,25 @@ is tested on metrics after they have passed the `tagpass` test.
 > tables. This limitation does not apply when using the inline table
 > syntax (`{...}`).
 
+- **metricpass**:
+A ["Common Expression Language"][CEL] (CEL) expression with boolean result where
+`true` will allow the metric to pass, otherwise the metric is discarded. This
+filter expression is more general compared to e.g. `namepass` and also allows
+for time-based filtering. An introduction to the CEL language can be found
+[here][CEL intro]. Further details, such as available functions and expressions,
+are provided in the [language definition][CEL lang] as well as in the
+[extension documentation][CEL ext].
+
+> NOTE: As CEL is an _interpreted_ languguage, this type of filtering is much
+> slower compared to `namepass`/`namedrop` and friends. So consider to use the
+> more restricted filter options where possible in case of high-throughput
+> scenarios.
+
+[CEL]:https://github.com/google/cel-go/tree/master
+[CEL intro]: https://codelabs.developers.google.com/codelabs/cel-go
+[CEL lang]: https://github.com/google/cel-spec/blob/master/doc/langdef.md
+[CEL ext]: https://github.com/google/cel-go/tree/master/ext#readme
+
 ### Modifiers
 
 Modifier filters remove tags and fields from a metric.  If all fields are

docs/LICENSE_OF_DEPENDENCIES.md

@@ -40,6 +40,7 @@ following works:
 - github.com/antchfx/jsonquery [MIT License](https://github.com/antchfx/jsonquery/blob/master/LICENSE)
 - github.com/antchfx/xmlquery [MIT License](https://github.com/antchfx/xmlquery/blob/master/LICENSE)
 - github.com/antchfx/xpath [MIT License](https://github.com/antchfx/xpath/blob/master/LICENSE)
+- github.com/antlr/antlr4/runtime/Go/antlr [BSD 3-Clause "New" or "Revised" License](https://github.com/antlr/antlr4/blob/master/LICENSE.txt)
 - github.com/apache/arrow/go/arrow [Apache License 2.0](https://github.com/apache/arrow/blob/master/LICENSE.txt)
 - github.com/apache/iotdb-client-go [Apache License 2.0](https://github.com/apache/iotdb-client-go/blob/main/LICENSE)
 - github.com/apache/thrift [Apache License 2.0](https://github.com/apache/thrift/blob/master/LICENSE)
@@ -141,6 +142,7 @@ following works:
 - github.com/golang/groupcache [Apache License 2.0](https://github.com/golang/groupcache/blob/master/LICENSE)
 - github.com/golang/protobuf [BSD 3-Clause "New" or "Revised" License](https://github.com/golang/protobuf/blob/master/LICENSE)
 - github.com/golang/snappy [BSD 3-Clause "New" or "Revised" License](https://github.com/golang/snappy/blob/master/LICENSE)
+- github.com/google/cel-go [Apache License 2.0](https://github.com/google/cel-go/blob/master/LICENSE)
 - github.com/google/flatbuffers [Apache License 2.0](https://github.com/google/flatbuffers/blob/master/LICENSE)
 - github.com/google/gnostic [Apache License 2.0](https://github.com/google/gnostic/blob/master/LICENSE)
 - github.com/google/gnxi [Apache License 2.0](https://github.com/google/gnxi/blob/master/LICENSE)
@@ -298,6 +300,7 @@ following works:
 - github.com/sleepinggenius2/gosmi [MIT License](https://github.com/sleepinggenius2/gosmi/blob/master/LICENSE)
 - github.com/snowflakedb/gosnowflake [Apache License 2.0](https://github.com/snowflakedb/gosnowflake/blob/master/LICENSE)
 - github.com/spf13/pflag [BSD 3-Clause "New" or "Revised" License](https://github.com/spf13/pflag/blob/master/LICENSE)
+- github.com/stoewer/go-strcase [MIT License](https://github.com/stoewer/go-strcase/blob/master/LICENSE)
 - github.com/stretchr/objx [MIT License](https://github.com/stretchr/objx/blob/master/LICENSE)
 - github.com/stretchr/testify [MIT License](https://github.com/stretchr/testify/blob/master/LICENSE)
 - github.com/testcontainers/testcontainers-go [MIT License](https://github.com/testcontainers/testcontainers-go/blob/main/LICENSE)

go.mod

@@ -200,6 +200,12 @@ require (
 	modernc.org/sqlite v1.21.0
 )
 
+require (
+	github.com/antlr/antlr4/runtime/Go/antlr/v4 v4.0.0-20230305170008-8188dc5388df // indirect
+	github.com/google/cel-go v0.14.1-0.20230424164844-d39523c445fc
+	github.com/stoewer/go-strcase v1.2.0 // indirect
+)
+
 require (
 	cloud.google.com/go v0.107.0 // indirect
 	cloud.google.com/go/compute v1.15.1 // indirect

go.sum

@@ -261,6 +261,8 @@ github.com/antchfx/xpath v1.2.4 h1:dW1HB/JxKvGtJ9WyVGJ0sIoEcqftV3SqIstujI+B9XY=
 github.com/antchfx/xpath v1.2.4/go.mod h1:i54GszH55fYfBmoZXapTHN8T8tkcHfRgLyVwwqzXNcs=
 github.com/antihax/optional v0.0.0-20180407024304-ca021399b1a6/go.mod h1:V8iCPQYkqmusNa815XgQio277wI47sdRh1dUOLdyC6Q=
 github.com/antihax/optional v1.0.0/go.mod h1:uupD/76wgC+ih3iEmQUL+0Ugr19nfwCT1kdvxnR2qWY=
+github.com/antlr/antlr4/runtime/Go/antlr/v4 v4.0.0-20230305170008-8188dc5388df h1:7RFfzj4SSt6nnvCPbCqijJi1nWCd+TqAT3bYCStRC18=
+github.com/antlr/antlr4/runtime/Go/antlr/v4 v4.0.0-20230305170008-8188dc5388df/go.mod h1:pSwJ0fSY5KhvocuWSx4fz3BA8OrA1bQn+K1Eli3BRwM=
 github.com/antonmedv/expr v1.9.0/go.mod h1:5qsM3oLGDND7sDmQGDXHkYfkjYMUX14qsgqmHhwGEk8=
 github.com/apache/arrow/go/arrow v0.0.0-20191024131854-af6fa24be0db/go.mod h1:VTxUBvSJ3s3eHAg65PNgrsn5BtqCRPdmyXh6rAfdxN0=
 github.com/apache/arrow/go/arrow v0.0.0-20211112161151-bc219186db40 h1:q4dksr6ICHXqG5hm0ZW5IHyeEJXoIJSOZeBLmWPNeIQ=
@@ -1012,6 +1014,8 @@ github.com/google/addlicense v0.0.0-20200906110928-a0294312aa76/go.mod h1:EMjYTR
 github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/btree v1.0.0/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/btree v1.0.1 h1:gK4Kx5IaGY9CD5sPJ36FHiBJ6ZXl0kilRiiCj+jdYp4=
+github.com/google/cel-go v0.14.1-0.20230424164844-d39523c445fc h1:jd+stC3Fqf9kaqgCLOdm4Da/AN3txPTlmLB6tStXAcU=
+github.com/google/cel-go v0.14.1-0.20230424164844-d39523c445fc/go.mod h1:YzWEoI07MC/a/wj9in8GeVatqfypkldgBlwXh9bCwqY=
 github.com/google/flatbuffers v1.11.0/go.mod h1:1AeVuKshWv4vARoZatz6mlQ0JxURH0Kv5+zNeJKJCa8=
 github.com/google/flatbuffers v1.12.1/go.mod h1:1AeVuKshWv4vARoZatz6mlQ0JxURH0Kv5+zNeJKJCa8=
 github.com/google/flatbuffers v2.0.0+incompatible h1:dicJ2oXwypfwUGnB2/TYWYEKiuk9eYQlQO/AnOHl5mI=
@@ -2146,6 +2150,7 @@ github.com/spf13/viper v1.7.1/go.mod h1:8WkrPz2fc9jxqZNCJI/76HCieCp4Q8HaLFoCha5q
 github.com/spf13/viper v1.11.0/go.mod h1:djo0X/bA5+tYVoCn+C7cAYJGcVn/qYLFTG8gdUsX7Zk=
 github.com/spf13/viper v1.12.0/go.mod h1:b6COn30jlNxbm/V2IqWiNWkJ+vZNiMNksliPCiuKtSI=
 github.com/ssgreg/nlreturn/v2 v2.1.0/go.mod h1:E/iiPB78hV7Szg2YfRgyIrk1AD6JVMTRkkxBiELzh2I=
+github.com/stoewer/go-strcase v1.2.0 h1:Z2iHWqGXH00XYgqDmNgQbIBxf3wrNq0F3feEy0ainaU=
 github.com/stoewer/go-strcase v1.2.0/go.mod h1:IBiWB2sKIp3wVVQ3Y035++gc+knqhUQag1KpM8ahLw8=
 github.com/streadway/amqp v0.0.0-20190404075320-75d898a42a94/go.mod h1:AZpEONHx3DKn8O/DFsRAY58/XVQiIPMTMB1SddzLXVw=
 github.com/streadway/amqp v0.0.0-20190827072141-edfb9018d271/go.mod h1:AZpEONHx3DKn8O/DFsRAY58/XVQiIPMTMB1SddzLXVw=

models/filter.go

@@ -1,7 +1,16 @@
 package models
 
 import (
+	"errors"
 	"fmt"
+	"regexp"
+	"time"
+
+	"github.com/google/cel-go/cel"
+	"github.com/google/cel-go/checker/decls"
+	"github.com/google/cel-go/common/types"
+	"github.com/google/cel-go/common/types/ref"
+	"github.com/google/cel-go/ext"
 
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/filter"
@@ -43,81 +52,111 @@ type Filter struct {
 	TagInclude       []string
 	tagIncludeFilter filter.Filter
 
+	// New metric-filtering interface
+	MetricPass   string
+	metricFilter cel.Program
+
+	selectActive bool
+	modifyActive bool
+
 	isActive bool
 }
 
 // Compile all Filter lists into filter.Filter objects.
 func (f *Filter) Compile() error {
-	if len(f.NameDrop) == 0 &&
+	f.selectActive = len(f.NamePass) > 0 || len(f.NameDrop) > 0
-		len(f.NamePass) == 0 &&
+	f.selectActive = f.selectActive || len(f.TagPassFilters) > 0 || len(f.TagDropFilters) > 0
-		len(f.FieldDrop) == 0 &&
+	f.selectActive = f.selectActive || f.MetricPass != ""
-		len(f.FieldPass) == 0 &&
+
-		len(f.TagInclude) == 0 &&
+	f.modifyActive = len(f.FieldPass) > 0 || len(f.FieldDrop) > 0
-		len(f.TagExclude) == 0 &&
+	f.modifyActive = f.modifyActive || len(f.TagInclude) > 0 || len(f.TagExclude) > 0
-		len(f.TagPassFilters) == 0 &&
+
-		len(f.TagDropFilters) == 0 {
+	f.isActive = f.selectActive || f.modifyActive
+
+	if !f.isActive {
 		return nil
 	}
 
-	f.isActive = true
+	if f.selectActive {
-	var err error
+		var err error
-	f.nameDropFilter, err = filter.Compile(f.NameDrop)
+		f.nameDropFilter, err = filter.Compile(f.NameDrop)
-	if err != nil {
+		if err != nil {
-		return fmt.Errorf("error compiling 'namedrop', %w", err)
+			return fmt.Errorf("error compiling 'namedrop', %w", err)
-	}
+		}
-	f.namePassFilter, err = filter.Compile(f.NamePass)
+		f.namePassFilter, err = filter.Compile(f.NamePass)
-	if err != nil {
+		if err != nil {
-		return fmt.Errorf("error compiling 'namepass', %w", err)
+			return fmt.Errorf("error compiling 'namepass', %w", err)
-	}
+		}
 
-	f.fieldDropFilter, err = filter.Compile(f.FieldDrop)
+		for i := range f.TagPassFilters {
-	if err != nil {
+			if err := f.TagPassFilters[i].Compile(); err != nil {
-		return fmt.Errorf("error compiling 'fielddrop', %w", err)
+				return fmt.Errorf("error compiling 'tagpass', %w", err)
-	}
+			}
-	f.fieldPassFilter, err = filter.Compile(f.FieldPass)
+		}
-	if err != nil {
+		for i := range f.TagDropFilters {
-		return fmt.Errorf("error compiling 'fieldpass', %w", err)
+			if err := f.TagDropFilters[i].Compile(); err != nil {
-	}
+				return fmt.Errorf("error compiling 'tagdrop', %w", err)
-
+			}
-	f.tagExcludeFilter, err = filter.Compile(f.TagExclude)
-	if err != nil {
-		return fmt.Errorf("error compiling 'tagexclude', %w", err)
-	}
-	f.tagIncludeFilter, err = filter.Compile(f.TagInclude)
-	if err != nil {
-		return fmt.Errorf("error compiling 'taginclude', %w", err)
-	}
-
-	for i := 0; i < len(f.TagDropFilters); i++ {
-		if err := f.TagDropFilters[i].Compile(); err != nil {
-			return fmt.Errorf("error compiling 'tagdrop', %w", err)
 		}
 	}
 
-	for i := 0; i < len(f.TagPassFilters); i++ {
+	if f.modifyActive {
-		if err := f.TagPassFilters[i].Compile(); err != nil {
+		var err error
-			return fmt.Errorf("error compiling 'tagpass', %w", err)
+		f.fieldDropFilter, err = filter.Compile(f.FieldDrop)
+		if err != nil {
+			return fmt.Errorf("error compiling 'fielddrop', %w", err)
+		}
+		f.fieldPassFilter, err = filter.Compile(f.FieldPass)
+		if err != nil {
+			return fmt.Errorf("error compiling 'fieldpass', %w", err)
+		}
+
+		f.tagExcludeFilter, err = filter.Compile(f.TagExclude)
+		if err != nil {
+			return fmt.Errorf("error compiling 'tagexclude', %w", err)
+		}
+		f.tagIncludeFilter, err = filter.Compile(f.TagInclude)
+		if err != nil {
+			return fmt.Errorf("error compiling 'taginclude', %w", err)
 		}
 	}
-	return nil
+
+	return f.compileMetricFilter()
 }
 
 // Select returns true if the metric matches according to the
-// namepass/namedrop and tagpass/tagdrop filters.  The metric is not modified.
+// namepass/namedrop, tagpass/tagdrop and metric filters.
-func (f *Filter) Select(metric telegraf.Metric) bool {
+// The metric is not modified.
-	if !f.isActive {
+func (f *Filter) Select(metric telegraf.Metric) (bool, error) {
-		return true
+	if !f.selectActive {
+		return true, nil
 	}
 
 	if !f.shouldNamePass(metric.Name()) {
-		return false
+		return false, nil
 	}
 
 	if !f.shouldTagsPass(metric.TagList()) {
-		return false
+		return false, nil
 	}
 
-	return true
+	if f.metricFilter != nil {
+		result, _, err := f.metricFilter.Eval(map[string]interface{}{
+			"name":   metric.Name(),
+			"tags":   metric.Tags(),
+			"fields": metric.Fields(),
+			"time":   metric.Time(),
+		})
+		if err != nil {
+			return true, err
+		}
+		if r, ok := result.Value().(bool); ok {
+			return r, nil
+		}
+		return true, fmt.Errorf("invalid result type %T", result.Value())
+	}
+
+	return true, nil
 }
 
 // Modify removes any tags and fields from the metric according to the
@@ -210,6 +249,63 @@ func (f *Filter) filterTags(metric telegraf.Metric) {
 	}
 }
 
+// Compile the metric filter
+func (f *Filter) compileMetricFilter() error {
+	// Reset internal state
+	f.metricFilter = nil
+
+	// Initialize the expression
+	expression := f.MetricPass
+
+	// Replace python-like logic-operators
+	expression = regexp.MustCompile(`\bnot\b`).ReplaceAllString(expression, "!")
+	expression = regexp.MustCompile(`\band\b`).ReplaceAllString(expression, "&&")
+	expression = regexp.MustCompile(`\bor\b`).ReplaceAllString(expression, "||")
+
+	// Check if we need to call into CEL at all and quit early
+	if expression == "" {
+		return nil
+	}
+
+	// Declare the computation environment for the filter including custom functions
+	env, err := cel.NewEnv(
+		cel.Declarations(
+			decls.NewVar("name", decls.String),
+			decls.NewVar("tags", decls.NewMapType(decls.String, decls.String)),
+			decls.NewVar("fields", decls.NewMapType(decls.String, decls.Dyn)),
+			decls.NewVar("time", decls.Timestamp),
+		),
+		cel.Function(
+			"now",
+			cel.Overload("now", nil, cel.TimestampType),
+			cel.SingletonFunctionBinding(func(_ ...ref.Val) ref.Val { return types.Timestamp{Time: time.Now()} }),
+		),
+		ext.Encoders(),
+		ext.Math(),
+		ext.Strings(),
+	)
+	if err != nil {
+		return fmt.Errorf("creating environment failed: %w", err)
+	}
+
+	// Compile the program
+	ast, issues := env.Compile(expression)
+	if issues.Err() != nil {
+		return issues.Err()
+	}
+	// Check if we got a boolean expression needed for filtering
+	if ast.OutputType() != cel.BoolType {
+		return errors.New("expression needs to return a boolean")
+	}
+
+	// Get the final program
+	options := cel.EvalOptions(
+		cel.OptOptimize,
+	)
+	f.metricFilter, err = env.Program(ast, options)
+	return err
+}
+
 func ShouldPassFilters(include filter.Filter, exclude filter.Filter, key string) bool {
 	if include != nil && exclude != nil {
 		return include.Match(key) && !exclude.Match(key)

models/filter_test.go

@@ -20,7 +20,9 @@ func TestFilter_ApplyEmpty(t *testing.T) {
 		map[string]string{},
 		map[string]interface{}{"value": int64(1)},
 		time.Now())
-	require.True(t, f.Select(m))
+	selected, err := f.Select(m)
+	require.NoError(t, err)
+	require.True(t, selected)
 }
 
 func TestFilter_ApplyTagsDontPass(t *testing.T) {
@@ -41,7 +43,9 @@ func TestFilter_ApplyTagsDontPass(t *testing.T) {
 		map[string]string{"cpu": "cpu-total"},
 		map[string]interface{}{"value": int64(1)},
 		time.Now())
-	require.False(t, f.Select(m))
+	selected, err := f.Select(m)
+	require.NoError(t, err)
+	require.False(t, selected)
 }
 
 func TestFilter_ApplyDeleteFields(t *testing.T) {
@@ -59,7 +63,9 @@ func TestFilter_ApplyDeleteFields(t *testing.T) {
 			"value2": int64(2),
 		},
 		time.Now())
-	require.True(t, f.Select(m))
+	selected, err := f.Select(m)
+	require.NoError(t, err)
+	require.True(t, selected)
 	f.Modify(m)
 	require.Equal(t, map[string]interface{}{"value2": int64(2)}, m.Fields())
 }
@@ -79,7 +85,9 @@ func TestFilter_ApplyDeleteAllFields(t *testing.T) {
 			"value2": int64(2),
 		},
 		time.Now())
-	require.True(t, f.Select(m))
+	selected, err := f.Select(m)
+	require.NoError(t, err)
+	require.True(t, selected)
 	f.Modify(m)
 	require.Len(t, m.FieldList(), 0)
 }
@@ -465,7 +473,6 @@ func TestFilter_FilterTagsPassAndDrop(t *testing.T) {
 		TagDropFilters: filterDrop,
 		TagPassFilters: filterPass,
 	}
-
 	require.NoError(t, f.Compile())
 
 	for i, tag := range inputData {
@@ -473,6 +480,118 @@ func TestFilter_FilterTagsPassAndDrop(t *testing.T) {
 	}
 }
 
+func TestFilter_MetricPass(t *testing.T) {
+	m := testutil.MustMetric("cpu",
+		map[string]string{
+			"host":   "Hugin",
+			"source": "myserver@mycompany.com",
+			"status": "ok",
+		},
+		map[string]interface{}{
+			"value":  15.0,
+			"id":     "24cxnwr3480k",
+			"on":     true,
+			"count":  18,
+			"errors": 29,
+			"total":  129,
+		},
+		time.Date(2023, time.April, 24, 23, 30, 15, 42, time.UTC),
+	)
+
+	var tests = []struct {
+		name       string
+		expression string
+		expected   bool
+	}{
+		{
+			name:     "empty",
+			expected: true,
+		},
+		{
+			name:       "exact name match (pass)",
+			expression: `name == "cpu"`,
+			expected:   true,
+		},
+		{
+			name:       "exact name match (fail)",
+			expression: `name == "test"`,
+			expected:   false,
+		},
+		{
+			name:       "case-insensitive tag match",
+			expression: `tags.host.lowerAscii() == "hugin"`,
+			expected:   true,
+		},
+		{
+			name:       "regexp tag match",
+			expression: `tags.source.matches("^[0-9a-zA-z-_]+@mycompany.com$")`,
+			expected:   true,
+		},
+		{
+			name:       "match field value",
+			expression: `fields.count > 10`,
+			expected:   true,
+		},
+		{
+			name:       "match timestamp year",
+			expression: `time.getFullYear() == 2023`,
+			expected:   true,
+		},
+		{
+			name:       "now",
+			expression: `now() > time`,
+			expected:   true,
+		},
+		{
+			name:       "arithmetics",
+			expression: `fields.count + fields.errors < fields.total`,
+			expected:   true,
+		},
+		{
+			name:       "arithmetics",
+			expression: `fields.count + fields.errors < fields.total`,
+			expected:   true,
+		},
+		{
+			name:       "logical expression",
+			expression: `(name.startsWith("t") || fields.on) && "id" in fields && fields.id.contains("nwr")`,
+			expected:   true,
+		},
+		{
+			name:       "python-style logical expression",
+			expression: `(name.startsWith("t") or fields.on) and "id" in fields and fields.id.contains("nwr")`,
+			expected:   true,
+		},
+		{
+			name:       "time arithmetics",
+			expression: `time >= timestamp("2023-04-25T00:00:00Z") - duration("24h")`,
+			expected:   true,
+		},
+		{
+			name:       "complex field filtering",
+			expression: `fields.exists(f, type(fields[f]) in [int, uint, double] and fields[f] > 20.0)`,
+			expected:   true,
+		},
+		{
+			name:       "complex field filtering (exactly one)",
+			expression: `fields.exists_one(f, type(fields[f]) in [int, uint, double] and fields[f] > 20.0)`,
+			expected:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f := Filter{
+				MetricPass: tt.expression,
+			}
+			require.NoError(t, f.Compile())
+			selected, err := f.Select(m)
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, selected)
+		})
+	}
+}
+
 func BenchmarkFilter(b *testing.B) {
 	tests := []struct {
 		name   string
@@ -503,13 +622,68 @@ func BenchmarkFilter(b *testing.B) {
 				time.Unix(0, 0),
 			),
 		},
+		{
+			name: "metric filter exact name",
+			filter: Filter{
+				MetricPass: `name == "cpu"`,
+			},
+			metric: testutil.MustMetric("cpu",
+				map[string]string{},
+				map[string]interface{}{
+					"value": 42,
+				},
+				time.Unix(0, 0),
+			),
+		},
+		{
+			name: "metric filter regexp",
+			filter: Filter{
+				MetricPass: `name.matches("^c[a-z]*$")`,
+			},
+			metric: testutil.MustMetric("cpu",
+				map[string]string{},
+				map[string]interface{}{
+					"value": 42,
+				},
+				time.Unix(0, 0),
+			),
+		},
+		{
+			name: "metric filter time",
+			filter: Filter{
+				MetricPass: `time >= timestamp("2023-04-25T00:00:00Z") - duration("24h")`,
+			},
+			metric: testutil.MustMetric("cpu",
+				map[string]string{},
+				map[string]interface{}{
+					"value": 42,
+				},
+				time.Unix(0, 0),
+			),
+		},
+		{
+			name: "metric filter complex",
+			filter: Filter{
+				MetricPass: `"source" in tags` +
+					` and fields.exists(f, type(fields[f]) in [int, uint, double] and fields[f] > 20.0)` +
+					` and time >= timestamp("2023-04-25T00:00:00Z") - duration("24h")`,
+			},
+			metric: testutil.MustMetric("cpu",
+				map[string]string{},
+				map[string]interface{}{
+					"value": 42,
+				},
+				time.Unix(0, 0),
+			),
+		},
 	}
 
 	for _, tt := range tests {
 		b.Run(tt.name, func(b *testing.B) {
 			require.NoError(b, tt.filter.Compile())
 			for n := 0; n < b.N; n++ {
-				tt.filter.Select(tt.metric)
+				_, err := tt.filter.Select(tt.metric)
+				require.NoError(b, err)
 			}
 		})
 	}

models/running_aggregator.go

@@ -133,7 +133,10 @@ func (r *RunningAggregator) MakeMetric(telegrafMetric telegraf.Metric) telegraf.
 // Add a metric to the aggregator and return true if the original metric
 // should be dropped.
 func (r *RunningAggregator) Add(m telegraf.Metric) bool {
-	if ok := r.Config.Filter.Select(m); !ok {
+	ok, err := r.Config.Filter.Select(m)
+	if err != nil {
+		r.log.Errorf("filtering failed: %v", err)
+	} else if !ok {
 		return false
 	}
 

models/running_input.go

@@ -97,7 +97,10 @@ func (r *RunningInput) ID() string {
 }
 
 func (r *RunningInput) MakeMetric(metric telegraf.Metric) telegraf.Metric {
-	if ok := r.Config.Filter.Select(metric); !ok {
+	ok, err := r.Config.Filter.Select(metric)
+	if err != nil {
+		r.log.Errorf("filtering failed: %v", err)
+	} else if !ok {
 		r.metricFiltered(metric)
 		return nil
 	}

models/running_output.go

@@ -139,7 +139,10 @@ func (r *RunningOutput) ID() string {
 // AddMetric adds a metric to the output.
 // Takes ownership of metric
 func (r *RunningOutput) AddMetric(metric telegraf.Metric) {
-	if ok := r.Config.Filter.Select(metric); !ok {
+	ok, err := r.Config.Filter.Select(metric)
+	if err != nil {
+		r.log.Errorf("filtering failed: %v", err)
+	} else if !ok {
 		r.metricFiltered(metric)
 		return
 	}

models/running_processor.go

@@ -87,7 +87,10 @@ func (rp *RunningProcessor) Start(acc telegraf.Accumulator) error {
 }
 
 func (rp *RunningProcessor) Add(m telegraf.Metric, acc telegraf.Accumulator) error {
-	if ok := rp.Config.Filter.Select(m); !ok {
+	ok, err := rp.Config.Filter.Select(m)
+	if err != nil {
+		rp.log.Errorf("filtering failed: %v", err)
+	} else if !ok {
 		// pass downstream
 		acc.AddMetric(m)
 		return nil