fix: reliability and 429 backoff (#9)

cmd/octopus_exporter/client.go

@@ -6,11 +6,17 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"net/http"
 	"strconv"
+	"strings"
+	"time"
 )
 
-var octopusGraphQL = "https://api.octopus.energy/v1/graphql/"
+var (
+	octopusGraphQL = "https://api.octopus.energy/v1/graphql/"
+	httpClient     = &http.Client{Timeout: 15 * time.Second}
+)
 
 type gqlRequest struct {
 	OperationName string         `json:"operationName,omitempty"`
@@ -39,25 +45,62 @@ func (f *jsonFloat) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
+// executeWithRetry executes an HTTP request, retrying on 429 with exponential
+// backoff (honouring Retry-After when present). Returns the raw response body.
+func executeWithRetry(makeReq func() (*http.Request, error)) ([]byte, error) {
+	const maxRetries = 5
+	backoff := 30 * time.Second
+	for attempt := 0; attempt <= maxRetries; attempt++ {
+		req, err := makeReq()
+		if err != nil {
+			return nil, err
+		}
+		resp, err := httpClient.Do(req)
+		if err != nil {
+			return nil, err
+		}
+		if resp.StatusCode == http.StatusTooManyRequests {
+			resp.Body.Close()
+			if attempt == maxRetries {
+				return nil, errors.New("rate limited: max retries exceeded")
+			}
+			wait := backoff
+			if ra := resp.Header.Get("Retry-After"); ra != "" {
+				if secs, err := strconv.Atoi(ra); err == nil {
+					wait = time.Duration(secs) * time.Second
+				}
+			}
+			log.Printf("rate limited; retrying in %v (attempt %d/%d)", wait, attempt+1, maxRetries)
+			time.Sleep(wait)
+			backoff *= 2
+			continue
+		}
+		raw, err := io.ReadAll(resp.Body)
+		resp.Body.Close()
+		if err != nil {
+			return nil, err
+		}
+		return raw, nil
+	}
+	return nil, errors.New("rate limited: max retries exceeded")
+}
+
 func doGraphQL(req gqlRequest, authToken string) (map[string]any, error) {
 	body, err := json.Marshal(req)
 	if err != nil {
 		return nil, err
 	}
-	httpReq, err := http.NewRequest(http.MethodPost, octopusGraphQL, bytes.NewReader(body))
-	if err != nil {
-		return nil, err
-	}
-	httpReq.Header.Set("Content-Type", "application/json")
-	if authToken != "" {
-		httpReq.Header.Set("Authorization", "JWT "+authToken)
-	}
-	resp, err := http.DefaultClient.Do(httpReq)
-	if err != nil {
-		return nil, err
-	}
-	defer resp.Body.Close()
-	raw, err := io.ReadAll(resp.Body)
+	raw, err := executeWithRetry(func() (*http.Request, error) {
+		httpReq, err := http.NewRequest(http.MethodPost, octopusGraphQL, bytes.NewReader(body))
+		if err != nil {
+			return nil, err
+		}
+		httpReq.Header.Set("Content-Type", "application/json")
+		if authToken != "" {
+			httpReq.Header.Set("Authorization", "JWT "+authToken)
+		}
+		return httpReq, nil
+	})
 	if err != nil {
 		return nil, err
 	}
@@ -67,7 +110,11 @@ func doGraphQL(req gqlRequest, authToken string) (map[string]any, error) {
 	}
 	if errs, ok := result["errors"].([]any); ok && len(errs) > 0 {
 		if e, ok := errs[0].(map[string]any); ok {
-			return nil, fmt.Errorf("GraphQL error: %s", e["message"])
+			msg, _ := e["message"].(string)
+			if strings.Contains(msg, "JWT") && strings.Contains(msg, "expired") {
+				return nil, errTokenExpired
+			}
+			return nil, fmt.Errorf("GraphQL error: %s", msg)
 		}
 		return nil, errors.New("GraphQL error")
 	}

cmd/octopus_exporter/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"log"
 	"net/http"
 	"os"
@@ -43,7 +44,13 @@ func main() {
 		log.Fatalf("failed to get initial token: %v", err)
 	}
 
-	elecMeter, err := resolveMeter(token, electricity)
+	log.Println("discovering meters from account...")
+	candidates, err := getMeters(token)
+	if err != nil {
+		log.Fatalf("failed to discover meters: %v", err)
+	}
+
+	elecMeter, err := resolveMeter(candidates, electricity)
 	if err != nil {
 		log.Fatalf("failed to resolve electricity meter: %v", err)
 	}
@@ -51,7 +58,7 @@ func main() {
 		log.Fatal("no electricity smart meter found on account")
 	}
 
-	gasMeter, err := resolveMeter(token, gas)
+	gasMeter, err := resolveMeter(candidates, gas)
 	if err != nil {
 		log.Fatalf("failed to resolve gas meter: %v", err)
 	}
@@ -111,18 +118,28 @@ func main() {
 		}
 	}()
 
+	tryRefresh := func(err error) {
+		if !errors.Is(err, errTokenExpired) {
+			return
+		}
+		t, e := getKrakenToken(apiKey)
+		if e != nil {
+			log.Printf("token refresh failed: %v", e)
+			return
+		}
+		token = t
+	}
+
 	for {
 		// Electricity telemetry (live demand)
 		if elecMeter.deviceID != "" {
 			reading, err := getLiveConsumption(token, elecMeter.deviceID)
 			if err != nil {
 				log.Printf("electricity telemetry error: %v", err)
-				if token, err = getKrakenToken(apiKey); err != nil {
-					log.Printf("token refresh failed: %v", err)
-				}
+				tryRefresh(err)
 			} else {
 				elecDemand.Set(float64(reading.Demand))
-				if t, err := time.Parse("2006-01-02T15:04:05+00:00", reading.ReadAt); err == nil {
+				if t, err := time.Parse(time.RFC3339, reading.ReadAt); err == nil {
 					elecLastRead.Set(float64(t.Unix()))
 				}
 			}
@@ -133,9 +150,10 @@ func main() {
 			reading, err := getLiveConsumption(token, gasMeter.deviceID)
 			if err != nil {
 				log.Printf("gas telemetry error: %v", err)
+				tryRefresh(err)
 			} else {
 				gasDemand.Set(float64(reading.Demand))
-				if t, err := time.Parse("2006-01-02T15:04:05+00:00", reading.ReadAt); err == nil {
+				if t, err := time.Parse(time.RFC3339, reading.ReadAt); err == nil {
 					gasLastRead.Set(float64(t.Unix()))
 				}
 			}
@@ -167,6 +185,7 @@ func main() {
 		rates, err := getRates(token)
 		if err != nil {
 			log.Printf("rates error: %v", err)
+			tryRefresh(err)
 		} else {
 			unitRate := rates.ElectricityUnitRate
 			if rates.ElectricityIsAgile && rates.ElectricityProductCode != "" && rates.ElectricityTariffCode != "" {
@@ -190,6 +209,7 @@ func main() {
 		balance, err := getAccountBalance(token)
 		if err != nil {
 			log.Printf("account balance error: %v", err)
+			tryRefresh(err)
 		} else {
 			accountBalance.Set(balance)
 		}

cmd/octopus_exporter/meters.go

@@ -57,7 +57,10 @@ func getMeters(token string) ([]meterCandidate, error) {
 	for _, a := range accounts {
 		props, _ := a.(map[string]any)["properties"].([]any)
 		for _, p := range props {
-			pm := p.(map[string]any)
+			pm, ok := p.(map[string]any)
+			if !ok {
+				continue
+			}
 
 			for _, mp := range toSlice(pm["electricityMeterPoints"]) {
 				mpan, _ := mp.(map[string]any)["mpan"].(string)
@@ -99,7 +102,7 @@ func getMeters(token string) ([]meterCandidate, error) {
 
 // resolveMeter finds the meter matching the env var filters for the given kind.
 // Returns (nil, nil) if no meter of that kind exists on the account.
-func resolveMeter(token string, kind meterKind) (*resolvedMeter, error) {
+func resolveMeter(candidates []meterCandidate, kind meterKind) (*resolvedMeter, error) {
 	var wantDeviceID, wantID, wantSerial string
 	switch kind {
 	case electricity:
@@ -112,12 +115,6 @@ func resolveMeter(token string, kind meterKind) (*resolvedMeter, error) {
 		wantSerial = os.Getenv("OCTOPUS_GAS_SERIAL")
 	}
 
-	log.Printf("discovering %s meters from account...", kind)
-	candidates, err := getMeters(token)
-	if err != nil {
-		return nil, err
-	}
-
 	for _, c := range candidates {
 		if c.kind != kind {
 			continue

cmd/octopus_exporter/rates.go

@@ -65,7 +65,11 @@ func getRates(token string) (*tariffRates, error) {
 
 // activeAgreementTariff returns the tariff map for the agreement with validTo == null.
 func activeAgreementTariff(meterPoint any) map[string]any {
-	for _, ag := range toSlice(meterPoint.(map[string]any)["agreements"]) {
+	mp, ok := meterPoint.(map[string]any)
+	if !ok {
+		return nil
+	}
+	for _, ag := range toSlice(mp["agreements"]) {
 		agm := ag.(map[string]any)
 		if agm["validTo"] == nil {
 			tariff, _ := agm["tariff"].(map[string]any)

cmd/octopus_exporter/rest.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"encoding/json"
-	"io"
 	"net/http"
 	"net/url"
 )
@@ -14,17 +13,14 @@ func doREST(path string, params url.Values) (map[string]any, error) {
 	if len(params) > 0 {
 		u += "?" + params.Encode()
 	}
-	req, err := http.NewRequest(http.MethodGet, u, nil)
-	if err != nil {
-		return nil, err
-	}
-	req.SetBasicAuth(apiKey, "")
-	resp, err := http.DefaultClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer resp.Body.Close()
-	raw, err := io.ReadAll(resp.Body)
+	raw, err := executeWithRetry(func() (*http.Request, error) {
+		req, err := http.NewRequest(http.MethodGet, u, nil)
+		if err != nil {
+			return nil, err
+		}
+		req.SetBasicAuth(apiKey, "")
+		return req, nil
+	})
 	if err != nil {
 		return nil, err
 	}

cmd/octopus_exporter/telemetry.go

@@ -18,9 +18,6 @@ func getLiveConsumption(token, deviceID string) (*telemetryReading, error) {
 		Query:         "query getSmartMeterTelemetry($meterDeviceId: String!, $start: DateTime, $end: DateTime, $grouping: TelemetryGrouping) {\n  smartMeterTelemetry(deviceId: $meterDeviceId, start: $start, end: $end, grouping: $grouping) {\n    readAt\n    consumption\n    demand\n    __typename\n  }\n}\n",
 	}, token)
 	if err != nil {
-		if err.Error() == "GraphQL error: Signature of the JWT has expired." {
-			return nil, errTokenExpired
-		}
 		return nil, err
 	}