Add storage.Warnings to client

Signed-off-by: Thomas Jackson <jacksontj.89@gmail.com>

Fixes #560

api/client.go

@@ -25,6 +25,42 @@ import (
 	"time"
 )
 
+func NewErrorAPI(err error, warnings []string) Error {
+	if err == nil && warnings == nil {
+		return nil
+	}
+	return &ErrorAPI{err, warnings}
+}
+
+type ErrorAPI struct {
+	err      error
+	warnings []string
+}
+
+func (w *ErrorAPI) Err() error {
+	return w.err
+}
+
+func (w *ErrorAPI) Error() string {
+	if w.err != nil {
+		return w.err.Error()
+	}
+	return "Warnings: " + strings.Join(w.warnings, " , ")
+}
+
+func (w *ErrorAPI) Warnings() []string {
+	return w.warnings
+}
+
+// Error encapsulates an error + warning
+type Error interface {
+	error
+	// Err returns the underlying error.
+	Err() error
+	// Warnings returns a list of warnings.
+	Warnings() []string
+}
+
 // DefaultRoundTripper is used if no RoundTripper is set in Config.
 var DefaultRoundTripper http.RoundTripper = &http.Transport{
 	Proxy: http.ProxyFromEnvironment,
@@ -55,14 +91,14 @@ func (cfg *Config) roundTripper() http.RoundTripper {
 // Client is the interface for an API client.
 type Client interface {
 	URL(ep string, args map[string]string) *url.URL
-	Do(context.Context, *http.Request) (*http.Response, []byte, error)
+	Do(context.Context, *http.Request) (*http.Response, []byte, Error)
 }
 
 // DoGetFallback will attempt to do the request as-is, and on a 405 it will fallback to a GET request.
-func DoGetFallback(c Client, ctx context.Context, u *url.URL, args url.Values) (*http.Response, []byte, error) {
+func DoGetFallback(c Client, ctx context.Context, u *url.URL, args url.Values) (*http.Response, []byte, Error) {
 	req, err := http.NewRequest(http.MethodPost, u.String(), strings.NewReader(args.Encode()))
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, NewErrorAPI(err, nil)
 	}
 	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 
@@ -71,11 +107,14 @@ func DoGetFallback(c Client, ctx context.Context, u *url.URL, args url.Values) (
 		u.RawQuery = args.Encode()
 		req, err = http.NewRequest(http.MethodGet, u.String(), nil)
 		if err != nil {
-			return nil, nil, err
+			return nil, nil, NewErrorAPI(err, nil)
 		}
 
 	} else {
-		return resp, body, err
+		if err != nil {
+			return resp, body, NewErrorAPI(err, nil)
+		}
+		return resp, body, nil
 	}
 	return c.Do(ctx, req)
 }
@@ -115,7 +154,7 @@ func (c *httpClient) URL(ep string, args map[string]string) *url.URL {
 	return &u
 }
 
-func (c *httpClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
+func (c *httpClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, Error) {
 	if ctx != nil {
 		req = req.WithContext(ctx)
 	}
@@ -127,7 +166,7 @@ func (c *httpClient) Do(ctx context.Context, req *http.Request) (*http.Response,
 	}()
 
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, NewErrorAPI(err, nil)
 	}
 
 	var body []byte
@@ -147,5 +186,5 @@ func (c *httpClient) Do(ctx context.Context, req *http.Request) (*http.Response,
 	case <-done:
 	}
 
-	return resp, body, err
+	return resp, body, NewErrorAPI(err, nil)
 }

api/prometheus/v1/api.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"net/http"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/prometheus/client_golang/api"
@@ -95,13 +96,26 @@ const (
 
 // Error is an error returned by the API.
 type Error struct {
-	Type   ErrorType
+	Type     ErrorType
-	Msg    string
+	Msg      string
-	Detail string
+	Detail   string
+	warnings []string
 }
 
 func (e *Error) Error() string {
-	return fmt.Sprintf("%s: %s", e.Type, e.Msg)
+	if e.Type != "" || e.Msg != "" {
+		return fmt.Sprintf("%s: %s", e.Type, e.Msg)
+	}
+
+	return "Warnings: " + strings.Join(e.warnings, " , ")
+}
+
+func (w *Error) Err() error {
+	return w
+}
+
+func (w *Error) Warnings() []string {
+	return w.warnings
 }
 
 // Range represents a sliced time range.
@@ -115,32 +129,32 @@ type Range struct {
 // API provides bindings for Prometheus's v1 API.
 type API interface {
 	// Alerts returns a list of all active alerts.
-	Alerts(ctx context.Context) (AlertsResult, error)
+	Alerts(ctx context.Context) (AlertsResult, api.Error)
 	// AlertManagers returns an overview of the current state of the Prometheus alert manager discovery.
-	AlertManagers(ctx context.Context) (AlertManagersResult, error)
+	AlertManagers(ctx context.Context) (AlertManagersResult, api.Error)
 	// CleanTombstones removes the deleted data from disk and cleans up the existing tombstones.
-	CleanTombstones(ctx context.Context) error
+	CleanTombstones(ctx context.Context) api.Error
 	// Config returns the current Prometheus configuration.
-	Config(ctx context.Context) (ConfigResult, error)
+	Config(ctx context.Context) (ConfigResult, api.Error)
 	// DeleteSeries deletes data for a selection of series in a time range.
-	DeleteSeries(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) error
+	DeleteSeries(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) api.Error
 	// Flags returns the flag values that Prometheus was launched with.
-	Flags(ctx context.Context) (FlagsResult, error)
+	Flags(ctx context.Context) (FlagsResult, api.Error)
 	// LabelValues performs a query for the values of the given label.
-	LabelValues(ctx context.Context, label string) (model.LabelValues, error)
+	LabelValues(ctx context.Context, label string) (model.LabelValues, api.Error)
 	// Query performs a query for the given time.
-	Query(ctx context.Context, query string, ts time.Time) (model.Value, error)
+	Query(ctx context.Context, query string, ts time.Time) (model.Value, api.Error)
 	// QueryRange performs a query for the given range.
-	QueryRange(ctx context.Context, query string, r Range) (model.Value, error)
+	QueryRange(ctx context.Context, query string, r Range) (model.Value, api.Error)
 	// Series finds series by label matchers.
-	Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, error)
+	Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, api.Error)
 	// Snapshot creates a snapshot of all current data into snapshots/<datetime>-<rand>
 	// under the TSDB's data directory and returns the directory as response.
-	Snapshot(ctx context.Context, skipHead bool) (SnapshotResult, error)
+	Snapshot(ctx context.Context, skipHead bool) (SnapshotResult, api.Error)
 	// Rules returns a list of alerting and recording rules that are currently loaded.
-	Rules(ctx context.Context) (RulesResult, error)
+	Rules(ctx context.Context) (RulesResult, api.Error)
 	// Targets returns an overview of the current state of the Prometheus target discovery.
-	Targets(ctx context.Context) (TargetsResult, error)
+	Targets(ctx context.Context) (TargetsResult, api.Error)
 }
 
 // AlertsResult contains the result from querying the alerts endpoint.
@@ -408,73 +422,73 @@ type httpAPI struct {
 	client api.Client
 }
 
-func (h *httpAPI) Alerts(ctx context.Context) (AlertsResult, error) {
+func (h *httpAPI) Alerts(ctx context.Context) (AlertsResult, api.Error) {
 	u := h.client.URL(epAlerts, nil)
 
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return AlertsResult{}, err
+		return AlertsResult{}, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return AlertsResult{}, err
+		return AlertsResult{}, apiErr
 	}
 
 	var res AlertsResult
 	err = json.Unmarshal(body, &res)
-	return res, err
+	return res, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) AlertManagers(ctx context.Context) (AlertManagersResult, error) {
+func (h *httpAPI) AlertManagers(ctx context.Context) (AlertManagersResult, api.Error) {
 	u := h.client.URL(epAlertManagers, nil)
 
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return AlertManagersResult{}, err
+		return AlertManagersResult{}, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return AlertManagersResult{}, err
+		return AlertManagersResult{}, apiErr
 	}
 
 	var res AlertManagersResult
 	err = json.Unmarshal(body, &res)
-	return res, err
+	return res, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) CleanTombstones(ctx context.Context) error {
+func (h *httpAPI) CleanTombstones(ctx context.Context) api.Error {
 	u := h.client.URL(epCleanTombstones, nil)
 
 	req, err := http.NewRequest(http.MethodPost, u.String(), nil)
 	if err != nil {
-		return err
+		return api.NewErrorAPI(err, nil)
 	}
 
-	_, _, err = h.client.Do(ctx, req)
+	_, _, apiErr := h.client.Do(ctx, req)
-	return err
+	return apiErr
 }
 
-func (h *httpAPI) Config(ctx context.Context) (ConfigResult, error) {
+func (h *httpAPI) Config(ctx context.Context) (ConfigResult, api.Error) {
 	u := h.client.URL(epConfig, nil)
 
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return ConfigResult{}, err
+		return ConfigResult{}, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return ConfigResult{}, err
+		return ConfigResult{}, apiErr
 	}
 
 	var res ConfigResult
 	err = json.Unmarshal(body, &res)
-	return res, err
+	return res, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) DeleteSeries(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) error {
+func (h *httpAPI) DeleteSeries(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) api.Error {
 	u := h.client.URL(epDeleteSeries, nil)
 	q := u.Query()
 
@@ -489,47 +503,47 @@ func (h *httpAPI) DeleteSeries(ctx context.Context, matches []string, startTime
 
 	req, err := http.NewRequest(http.MethodPost, u.String(), nil)
 	if err != nil {
-		return err
+		return api.NewErrorAPI(err, nil)
 	}
 
-	_, _, err = h.client.Do(ctx, req)
+	_, _, apiErr := h.client.Do(ctx, req)
-	return err
+	return apiErr
 }
 
-func (h *httpAPI) Flags(ctx context.Context) (FlagsResult, error) {
+func (h *httpAPI) Flags(ctx context.Context) (FlagsResult, api.Error) {
 	u := h.client.URL(epFlags, nil)
 
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return FlagsResult{}, err
+		return FlagsResult{}, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return FlagsResult{}, err
+		return FlagsResult{}, apiErr
 	}
 
 	var res FlagsResult
 	err = json.Unmarshal(body, &res)
-	return res, err
+	return res, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) LabelValues(ctx context.Context, label string) (model.LabelValues, error) {
+func (h *httpAPI) LabelValues(ctx context.Context, label string) (model.LabelValues, api.Error) {
 	u := h.client.URL(epLabelValues, map[string]string{"name": label})
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return nil, err
+		return nil, api.NewErrorAPI(err, nil)
 	}
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return nil, err
+		return nil, apiErr
 	}
 	var labelValues model.LabelValues
 	err = json.Unmarshal(body, &labelValues)
-	return labelValues, err
+	return labelValues, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) Query(ctx context.Context, query string, ts time.Time) (model.Value, error) {
+func (h *httpAPI) Query(ctx context.Context, query string, ts time.Time) (model.Value, api.Error) {
 	u := h.client.URL(epQuery, nil)
 	q := u.Query()
 
@@ -538,18 +552,16 @@ func (h *httpAPI) Query(ctx context.Context, query string, ts time.Time) (model.
 		q.Set("time", ts.Format(time.RFC3339Nano))
 	}
 
-	_, body, err := api.DoGetFallback(h.client, ctx, u, q)
+	_, body, apiErr := api.DoGetFallback(h.client, ctx, u, q)
-	if err != nil {
+	if apiErr != nil {
-		return nil, err
+		return nil, apiErr
 	}
 
 	var qres queryResult
-	err = json.Unmarshal(body, &qres)
+	return model.Value(qres.v), api.NewErrorAPI(json.Unmarshal(body, &qres), nil)
-
-	return model.Value(qres.v), err
 }
 
-func (h *httpAPI) QueryRange(ctx context.Context, query string, r Range) (model.Value, error) {
+func (h *httpAPI) QueryRange(ctx context.Context, query string, r Range) (model.Value, api.Error) {
 	u := h.client.URL(epQueryRange, nil)
 	q := u.Query()
 
@@ -564,18 +576,17 @@ func (h *httpAPI) QueryRange(ctx context.Context, query string, r Range) (model.
 	q.Set("end", end)
 	q.Set("step", step)
 
-	_, body, err := api.DoGetFallback(h.client, ctx, u, q)
+	_, body, apiErr := api.DoGetFallback(h.client, ctx, u, q)
-	if err != nil {
+	if apiErr != nil {
-		return nil, err
+		return nil, apiErr
 	}
 
 	var qres queryResult
-	err = json.Unmarshal(body, &qres)
 
-	return model.Value(qres.v), err
+	return model.Value(qres.v), api.NewErrorAPI(json.Unmarshal(body, &qres), nil)
 }
 
-func (h *httpAPI) Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, error) {
+func (h *httpAPI) Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, api.Error) {
 	u := h.client.URL(epSeries, nil)
 	q := u.Query()
 
@@ -590,20 +601,20 @@ func (h *httpAPI) Series(ctx context.Context, matches []string, startTime time.T
 
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return nil, err
+		return nil, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return nil, err
+		return nil, apiErr
 	}
 
 	var mset []model.LabelSet
 	err = json.Unmarshal(body, &mset)
-	return mset, err
+	return mset, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) Snapshot(ctx context.Context, skipHead bool) (SnapshotResult, error) {
+func (h *httpAPI) Snapshot(ctx context.Context, skipHead bool) (SnapshotResult, api.Error) {
 	u := h.client.URL(epSnapshot, nil)
 	q := u.Query()
 
@@ -613,53 +624,53 @@ func (h *httpAPI) Snapshot(ctx context.Context, skipHead bool) (SnapshotResult,
 
 	req, err := http.NewRequest(http.MethodPost, u.String(), nil)
 	if err != nil {
-		return SnapshotResult{}, err
+		return SnapshotResult{}, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return SnapshotResult{}, err
+		return SnapshotResult{}, apiErr
 	}
 
 	var res SnapshotResult
 	err = json.Unmarshal(body, &res)
-	return res, err
+	return res, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) Rules(ctx context.Context) (RulesResult, error) {
+func (h *httpAPI) Rules(ctx context.Context) (RulesResult, api.Error) {
 	u := h.client.URL(epRules, nil)
 
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return RulesResult{}, err
+		return RulesResult{}, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return RulesResult{}, err
+		return RulesResult{}, apiErr
 	}
 
 	var res RulesResult
 	err = json.Unmarshal(body, &res)
-	return res, err
+	return res, api.NewErrorAPI(err, nil)
 }
 
-func (h *httpAPI) Targets(ctx context.Context) (TargetsResult, error) {
+func (h *httpAPI) Targets(ctx context.Context) (TargetsResult, api.Error) {
 	u := h.client.URL(epTargets, nil)
 
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
-		return TargetsResult{}, err
+		return TargetsResult{}, api.NewErrorAPI(err, nil)
 	}
 
-	_, body, err := h.client.Do(ctx, req)
+	_, body, apiErr := h.client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return TargetsResult{}, err
+		return TargetsResult{}, apiErr
 	}
 
 	var res TargetsResult
 	err = json.Unmarshal(body, &res)
-	return res, err
+	return res, api.NewErrorAPI(err, nil)
 }
 
 // apiClient wraps a regular client and processes successful API responses.
@@ -673,6 +684,7 @@ type apiResponse struct {
 	Data      json.RawMessage `json:"data"`
 	ErrorType ErrorType       `json:"errorType"`
 	Error     string          `json:"error"`
+	Warnings  []string        `json:"warnings,omitempty"`
 }
 
 func apiError(code int) bool {
@@ -690,14 +702,16 @@ func errorTypeAndMsgFor(resp *http.Response) (ErrorType, string) {
 	return ErrBadResponse, fmt.Sprintf("bad response code %d", resp.StatusCode)
 }
 
-func (c apiClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
+func (c apiClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, api.Error) {
-	resp, body, err := c.Client.Do(ctx, req)
+	resp, body, apiErr := c.Client.Do(ctx, req)
-	if err != nil {
+	if apiErr != nil {
-		return resp, body, err
+		return resp, body, apiErr
 	}
 
 	code := resp.StatusCode
 
+	var err api.Error
+
 	if code/100 != 2 && !apiError(code) {
 		errorType, errorMsg := errorTypeAndMsgFor(resp)
 		return resp, body, &Error{
@@ -710,27 +724,30 @@ func (c apiClient) Do(ctx context.Context, req *http.Request) (*http.Response, [
 	var result apiResponse
 
 	if http.StatusNoContent != code {
-		if err = json.Unmarshal(body, &result); err != nil {
+		if jsonErr := json.Unmarshal(body, &result); jsonErr != nil {
 			return resp, body, &Error{
 				Type: ErrBadResponse,
-				Msg:  err.Error(),
+				Msg:  jsonErr.Error(),
 			}
 		}
 	}
 
 	if apiError(code) != (result.Status == "error") {
 		err = &Error{
-			Type: ErrBadResponse,
+			Type:     ErrBadResponse,
-			Msg:  "inconsistent body for response code",
+			Msg:      "inconsistent body for response code",
+			warnings: result.Warnings,
 		}
 	}
 
 	if apiError(code) && result.Status == "error" {
 		err = &Error{
-			Type: result.ErrorType,
+			Type:     result.ErrorType,
-			Msg:  result.Error,
+			Msg:      result.Error,
+			warnings: result.Warnings,
 		}
 	}
 
 	return resp, []byte(result.Data), err
+
 }

api/prometheus/v1/api_test.go

@@ -25,11 +25,14 @@ import (
 	"testing"
 	"time"
 
+	"github.com/prometheus/client_golang/api"
 	"github.com/prometheus/common/model"
+	"github.com/prometheus/tsdb/testutil"
 )
 
 type apiTest struct {
-	do           func() (interface{}, error)
+	do           func() (interface{}, api.Error)
+	inWarnings   []string
 	inErr        error
 	inStatusCode int
 	inRes        interface{}
@@ -58,7 +61,7 @@ func (c *apiTestClient) URL(ep string, args map[string]string) *url.URL {
 	return u
 }
 
-func (c *apiTestClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
+func (c *apiTestClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, api.Error) {
 
 	test := c.curTest
 
@@ -83,7 +86,7 @@ func (c *apiTestClient) Do(ctx context.Context, req *http.Request) (*http.Respon
 		resp.StatusCode = http.StatusOK
 	}
 
-	return resp, b, test.inErr
+	return resp, b, api.NewErrorAPI(test.inErr, test.inWarnings)
 }
 
 func TestAPIs(t *testing.T) {
@@ -96,74 +99,74 @@ func TestAPIs(t *testing.T) {
 		client: client,
 	}
 
-	doAlertManagers := func() func() (interface{}, error) {
+	doAlertManagers := func() func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.AlertManagers(context.Background())
 		}
 	}
 
-	doCleanTombstones := func() func() (interface{}, error) {
+	doCleanTombstones := func() func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return nil, promAPI.CleanTombstones(context.Background())
 		}
 	}
 
-	doConfig := func() func() (interface{}, error) {
+	doConfig := func() func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.Config(context.Background())
 		}
 	}
 
-	doDeleteSeries := func(matcher string, startTime time.Time, endTime time.Time) func() (interface{}, error) {
+	doDeleteSeries := func(matcher string, startTime time.Time, endTime time.Time) func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return nil, promAPI.DeleteSeries(context.Background(), []string{matcher}, startTime, endTime)
 		}
 	}
 
-	doFlags := func() func() (interface{}, error) {
+	doFlags := func() func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.Flags(context.Background())
 		}
 	}
 
-	doLabelValues := func(label string) func() (interface{}, error) {
+	doLabelValues := func(label string) func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.LabelValues(context.Background(), label)
 		}
 	}
 
-	doQuery := func(q string, ts time.Time) func() (interface{}, error) {
+	doQuery := func(q string, ts time.Time) func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.Query(context.Background(), q, ts)
 		}
 	}
 
-	doQueryRange := func(q string, rng Range) func() (interface{}, error) {
+	doQueryRange := func(q string, rng Range) func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.QueryRange(context.Background(), q, rng)
 		}
 	}
 
-	doSeries := func(matcher string, startTime time.Time, endTime time.Time) func() (interface{}, error) {
+	doSeries := func(matcher string, startTime time.Time, endTime time.Time) func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.Series(context.Background(), []string{matcher}, startTime, endTime)
 		}
 	}
 
-	doSnapshot := func(skipHead bool) func() (interface{}, error) {
+	doSnapshot := func(skipHead bool) func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.Snapshot(context.Background(), skipHead)
 		}
 	}
 
-	doRules := func() func() (interface{}, error) {
+	doRules := func() func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.Rules(context.Background())
 		}
 	}
 
-	doTargets := func() func() (interface{}, error) {
+	doTargets := func() func() (interface{}, api.Error) {
-		return func() (interface{}, error) {
+		return func() (interface{}, api.Error) {
 			return promAPI.Targets(context.Background())
 		}
 	}
@@ -693,7 +696,7 @@ func (c *testClient) URL(ep string, args map[string]string) *url.URL {
 	return nil
 }
 
-func (c *testClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
+func (c *testClient) Do(ctx context.Context, req *http.Request) (*http.Response, []byte, api.Error) {
 	if ctx == nil {
 		c.Fatalf("context was not passed down")
 	}
@@ -829,6 +832,21 @@ func TestAPIClientDo(t *testing.T) {
 				Msg:  "inconsistent body for response code",
 			},
 		},
+		{
+			code: http.StatusOK,
+			response: &apiResponse{
+				Status:    "error",
+				Data:      json.RawMessage(`"test"`),
+				ErrorType: ErrTimeout,
+				Error:     "timed out",
+				Warnings:  []string{"a"},
+			},
+			expectedErr: &Error{
+				Type:     ErrBadResponse,
+				Msg:      "inconsistent body for response code",
+				warnings: []string{"a"},
+			},
+		},
 	}
 
 	tc := &testClient{
@@ -846,28 +864,20 @@ func TestAPIClientDo(t *testing.T) {
 			_, body, err := client.Do(context.Background(), tc.req)
 
 			if test.expectedErr != nil {
-				if err == nil {
+				testutil.NotOk(t, err)
-					t.Fatalf("expected error %q but got none", test.expectedErr)
+				testutil.Equals(t, test.expectedErr.Error(), err.Error())
-				}
+
-				if test.expectedErr.Error() != err.Error() {
-					t.Errorf("unexpected error: want %q, got %q", test.expectedErr, err)
-				}
 				if test.expectedErr.Detail != "" {
 					apiErr := err.(*Error)
-					if apiErr.Detail != test.expectedErr.Detail {
+					testutil.Equals(t, apiErr.Detail, test.expectedErr.Detail)
-						t.Errorf("unexpected error details: want %q, got %q", test.expectedErr.Detail, apiErr.Detail)
-					}
 				}
+
+				testutil.Equals(t, test.expectedErr.Warnings(), err.Warnings())
 				return
 			}
-			if err != nil {
+			testutil.Ok(t, err)
-				t.Fatalf("unexpeceted error %s", err)
-			}
 
-			want, got := test.expectedBody, string(body)
+			testutil.Equals(t, test.expectedBody, string(body))
-			if want != got {
-				t.Errorf("unexpected body: want %q, got %q", want, got)
-			}
 		})
 
 	}

go.sum

@@ -1,3 +1,4 @@
+github.com/OneOfOne/xxhash v1.2.2 h1:KMrpdQIwFcEqXDklaen+P1axHaj9BSKzvpUUfnHldSE=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
@@ -5,7 +6,9 @@ github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973 h1:xJ4a3vCFaGF/jqvzLM
 github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
 github.com/beorn7/perks v1.0.0 h1:HWo1m869IqiPhD389kmkxeTalrjNbbJTC8LXupb+sl0=
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
+github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
 github.com/go-kit/kit v0.8.0 h1:Wz+5lgoB0kkuqLEc6NVmwRknTKP6dTGbSqvhZtBI/j0=
@@ -28,6 +31,7 @@ github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
 github.com/oklog/ulid v1.3.1/go.mod h1:CirwcVhetQ6Lv90oh/F+FBtV6XMibvdAFo93nm5qn4U=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
 github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910 h1:idejC8f05m9MGOsuEi1ATq9shN03HrxNkD/luQvxCv8=
@@ -43,8 +47,10 @@ github.com/prometheus/procfs v0.0.0-20190412120340-e22ddced7142/go.mod h1:TjEm7z
 github.com/prometheus/tsdb v0.7.1 h1:YZcsG11NqnK4czYLrWd9mpEuAJIHVQLwdrleYfszMAA=
 github.com/prometheus/tsdb v0.7.1/go.mod h1:qhTCs0VvXwvX/y3TZrWD7rabWM+ijKTux40TwIPHuXU=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72 h1:qLC7fQah7D6K1B0ujays3HV9gkFtllcxhzImRR7ArPQ=
 github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/net v0.0.0-20181114220301-adae6a3d119a/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=