Add /config handler which exposes the current YAML config of cortex. (#2165)

* Add /config handler which exposes the current YAML config of cortex.

Signed-off-by: Tom Wilkie <tom@grafana.com>
Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

* Add changelog and line to docs.

Signed-off-by: Tom Wilkie <tom@grafana.com>
Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

* Fix lint.

(Also regen docs)

Signed-off-by: Tom Wilkie <tom@grafana.com>
Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

* Fix marshalling / unmarshalling of flagext values and add test.

Signed-off-by: Tom Wilkie <tom@grafana.com>
Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

* Add PR number to changelog.

Signed-off-by: Tom Wilkie <tom@grafana.com>
Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

* Fixed linter

Signed-off-by: Marco Pracucci <marco@pracucci.com>

* Fixed URLValue zero value marshalling

Signed-off-by: Marco Pracucci <marco@pracucci.com>

* Removed omitempty from LifecyclerConfig

Signed-off-by: Marco Pracucci <marco@pracucci.com>

* Added integration test on GET /config endpoint

Signed-off-by: Marco Pracucci <marco@pracucci.com>

Co-authored-by: Marco Pracucci <marco@pracucci.com>

Author: tomwilkie

CHANGELOG.md

@@ -30,6 +30,7 @@
 * [FEATURE] Added sharding support to compactor when using the experimental TSDB blocks storage. #2113
 * [FEATURE] Add ability to override YAML config file settings using environment variables. #2147
   * `-config.expand-env`
+* [FEATURE] Add /config HTTP endpoint which exposes the current Cortex configuration as YAML. #2165
 * [ENHANCEMENT] Add `status` label to `cortex_alertmanager_configs` metric to gauge the number of valid and invalid configs. #2125
 * [ENHANCEMENT] Cassandra Authentication: added the `custom_authenticators` config option that allows users to authenticate with cassandra clusters using password authenticators that are not approved by default in [gocql](https://github.com/gocql/gocql/blob/81b8263d9fe526782a588ef94d3fa5c6148e5d67/conn.go#L27) #2093
 * [ENHANCEMENT] Experimental TSDB: Export TSDB Syncer metrics from Compactor component, they are prefixed with `cortex_compactor_`. #2023

docs/configuration/config-file-reference.md

@@ -7,6 +7,8 @@ slug: configuration-file
 
 Cortex can be configured using a YAML file - specified using the `-config.file` flag - or CLI flags. In case you combine both, CLI flags take precedence over the YAML config file.
 
+The current configuration of any Cortex component can be seen by visiting the `/config` HTTP path.
+
 ## Reference
 
 To specify which configuration file to load, pass the `-config.file` flag at the command line. The file is written in [YAML format](https://en.wikipedia.org/wiki/YAML), defined by the scheme below. Brackets indicate that a parameter is optional.

docs/configuration/config-file-reference.template

@@ -7,6 +7,8 @@ slug: configuration-file
 
 Cortex can be configured using a YAML file - specified using the `-config.file` flag - or CLI flags. In case you combine both, CLI flags take precedence over the YAML config file.
 
+The current configuration of any Cortex component can be seen by visiting the `/config` HTTP path.
+
 ## Reference
 
 To specify which configuration file to load, pass the `-config.file` flag at the command line. The file is written in [YAML format](https://en.wikipedia.org/wiki/YAML), defined by the scheme below. Brackets indicate that a parameter is optional.

integration/api_config_test.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"github.com/thanos-io/thanos/pkg/runutil"
+
+	"github.com/cortexproject/cortex/integration/e2e"
+	"github.com/cortexproject/cortex/integration/e2ecortex"
+)
+
+func TestConfigAPIEndpoint(t *testing.T) {
+	s, err := e2e.NewScenario(networkName)
+	require.NoError(t, err)
+	defer s.Close()
+
+	// Start Cortex in single binary mode, reading the config from file.
+	require.NoError(t, copyFileToSharedDir(s, "docs/configuration/single-process-config.yaml", cortexConfigFile))
+	flags := map[string]string{
+		"-config.file": filepath.Join(e2e.ContainerSharedDir, cortexConfigFile),
+	}
+
+	cortex1 := e2ecortex.NewSingleBinary("cortex-1", flags, "", 9009)
+	require.NoError(t, s.StartAndWaitReady(cortex1))
+
+	// Get config from /config API endpoint.
+	res, err := e2e.GetRequest(fmt.Sprintf("http://%s/config", cortex1.Endpoint(9009)))
+	require.NoError(t, err)
+	
+	defer runutil.ExhaustCloseWithErrCapture(&err, res.Body, "config API response")
+	body, err := ioutil.ReadAll(res.Body)
+	require.NoError(t, err)
+	require.Equal(t, http.StatusOK, res.StatusCode)
+
+	// Start again Cortex in single binary with the exported config
+	// and ensure it starts (pass the readiness probe).
+	require.NoError(t, writeFileToSharedDir(s, cortexConfigFile, body))
+	cortex2 := e2ecortex.NewSingleBinary("cortex-2", flags, "", 9009)
+	require.NoError(t, s.StartAndWaitReady(cortex2))
+}

pkg/cortex/modules.go

@@ -18,6 +18,7 @@ import (
 	"github.com/weaveworks/common/middleware"
 	"github.com/weaveworks/common/server"
 	"google.golang.org/grpc/health/grpc_health_v1"
+	"gopkg.in/yaml.v2"
 
 	"github.com/cortexproject/cortex/pkg/alertmanager"
 	"github.com/cortexproject/cortex/pkg/chunk"
@@ -167,9 +168,28 @@ func (m *moduleName) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	return m.Set(s)
 }
 
-func (t *Cortex) initServer(cfg *Config) (err error) {
+func (t *Cortex) initServer(cfg *Config) error {
+	var err error
 	t.server, err = server.New(cfg.Server)
-	return
+	if err != nil {
+		return err
+	}
+
+	t.server.HTTP.HandleFunc("/config", func(w http.ResponseWriter, _ *http.Request) {
+		out, err := yaml.Marshal(cfg)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		w.Header().Set("Content-Type", "text/yaml")
+		w.WriteHeader(http.StatusOK)
+		if _, err := w.Write(out); err != nil {
+			level.Error(util.Logger).Log("msg", "error writing response", "err", err)
+		}
+	})
+
+	return nil
 }
 
 func (t *Cortex) stopServer() (err error) {

pkg/ring/lifecycler.go

@@ -44,14 +44,14 @@ type LifecyclerConfig struct {
 
 	// Config for the ingester lifecycle control
 	ListenPort       *int          `yaml:"-"`
-	NumTokens        int           `yaml:"num_tokens,omitempty"`
-	HeartbeatPeriod  time.Duration `yaml:"heartbeat_period,omitempty"`
-	ObservePeriod    time.Duration `yaml:"observe_period,omitempty"`
-	JoinAfter        time.Duration `yaml:"join_after,omitempty"`
-	MinReadyDuration time.Duration `yaml:"min_ready_duration,omitempty"`
+	NumTokens        int           `yaml:"num_tokens"`
+	HeartbeatPeriod  time.Duration `yaml:"heartbeat_period"`
+	ObservePeriod    time.Duration `yaml:"observe_period"`
+	JoinAfter        time.Duration `yaml:"join_after"`
+	MinReadyDuration time.Duration `yaml:"min_ready_duration"`
 	InfNames         []string      `yaml:"interface_names"`
 	FinalSleep       time.Duration `yaml:"final_sleep"`
-	TokensFilePath   string        `yaml:"tokens_file_path,omitempty"`
+	TokensFilePath   string        `yaml:"tokens_file_path"`
 
 	// For testing, you can override the address and ID of this ingester
 	Addr           string `yaml:"address" doc:"hidden"`

pkg/util/flagext/day.go

@@ -43,3 +43,17 @@ func (v *DayValue) Set(s string) error {
 func (v *DayValue) IsSet() bool {
 	return v.set
 }
+
+// UnmarshalYAML implements yaml.Unmarshaler.
+func (v *DayValue) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var s string
+	if err := unmarshal(&s); err != nil {
+		return err
+	}
+	return v.Set(s)
+}
+
+// MarshalYAML implements yaml.Marshaler.
+func (v DayValue) MarshalYAML() (interface{}, error) {
+	return v.Time.Time().Format("2006-01-02"), nil
+}

pkg/util/flagext/day_test.go

@@ -0,0 +1,54 @@
+package flagext
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v2"
+)
+
+func TestDayValueYAML(t *testing.T) {
+	// Test embedding of DayValue.
+	{
+		type TestStruct struct {
+			Day DayValue `yaml:"day"`
+		}
+
+		var testStruct TestStruct
+		require.NoError(t, testStruct.Day.Set("1985-06-02"))
+		expected := []byte(`day: "1985-06-02"
+`)
+
+		actual, err := yaml.Marshal(testStruct)
+		require.NoError(t, err)
+		assert.Equal(t, expected, actual)
+
+		var actualStruct TestStruct
+		err = yaml.Unmarshal(expected, &actualStruct)
+		require.NoError(t, err)
+		assert.Equal(t, testStruct, actualStruct)
+	}
+
+	// Test pointers of DayValue.
+	{
+		type TestStruct struct {
+			Day *DayValue `yaml:"day"`
+		}
+
+		var testStruct TestStruct
+		testStruct.Day = &DayValue{}
+		require.NoError(t, testStruct.Day.Set("1985-06-02"))
+		expected := []byte(`day: "1985-06-02"
+`)
+
+		actual, err := yaml.Marshal(testStruct)
+		require.NoError(t, err)
+		assert.Equal(t, expected, actual)
+
+		var actualStruct TestStruct
+		err = yaml.Unmarshal(expected, &actualStruct)
+		require.NoError(t, err)
+		assert.Equal(t, testStruct, actualStruct)
+	}
+}

pkg/util/flagext/url.go

@@ -31,5 +31,21 @@ func (v *URLValue) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	if err := unmarshal(&s); err != nil {
 		return err
 	}
+
+	// An empty string means no URL has been configured.
+	if s == "" {
+		v.URL = nil
+		return nil
+	}
+
 	return v.Set(s)
 }
+
+// MarshalYAML implements yaml.Marshaler.
+func (v URLValue) MarshalYAML() (interface{}, error) {
+	if v.URL == nil {
+		return "", nil
+	}
+
+	return v.URL.String(), nil
+}

pkg/util/flagext/url_test.go

@@ -0,0 +1,74 @@
+package flagext
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v2"
+)
+
+func TestURLValueYAML(t *testing.T) {
+	// Test embedding of URLValue.
+	{
+		type TestStruct struct {
+			URL URLValue `yaml:"url"`
+		}
+
+		var testStruct TestStruct
+		require.NoError(t, testStruct.URL.Set("http://google.com"))
+		expected := []byte(`url: http://google.com
+`)
+
+		actual, err := yaml.Marshal(testStruct)
+		require.NoError(t, err)
+		assert.Equal(t, expected, actual)
+
+		var actualStruct TestStruct
+		err = yaml.Unmarshal(expected, &actualStruct)
+		require.NoError(t, err)
+		assert.Equal(t, testStruct, actualStruct)
+	}
+
+	// Test pointers of URLValue.
+	{
+		type TestStruct struct {
+			URL *URLValue `yaml:"url"`
+		}
+
+		var testStruct TestStruct
+		testStruct.URL = &URLValue{}
+		require.NoError(t, testStruct.URL.Set("http://google.com"))
+		expected := []byte(`url: http://google.com
+`)
+
+		actual, err := yaml.Marshal(testStruct)
+		require.NoError(t, err)
+		assert.Equal(t, expected, actual)
+
+		var actualStruct TestStruct
+		err = yaml.Unmarshal(expected, &actualStruct)
+		require.NoError(t, err)
+		assert.Equal(t, testStruct, actualStruct)
+	}
+
+	// Test no url set in URLValue.
+	{
+		type TestStruct struct {
+			URL URLValue `yaml:"url"`
+		}
+
+		var testStruct TestStruct
+		expected := []byte(`url: ""
+`)
+
+		actual, err := yaml.Marshal(testStruct)
+		require.NoError(t, err)
+		assert.Equal(t, expected, actual)
+
+		var actualStruct TestStruct
+		err = yaml.Unmarshal(expected, &actualStruct)
+		require.NoError(t, err)
+		assert.Equal(t, testStruct, actualStruct)
+	}
+}