client: check for zero fiat rates and response status code

This increases the request interval for fiat rates to 12min due to a
possibility of hitting source's request limits. This can be considered a
temporary solution since we need to adjust this interval for every added
asset.

This also checks the HTTP response status code instead of assuming
the response is the expected payload.

client/core/core.go

@@ -8031,7 +8031,7 @@ func (c *Core) fiatConversions() map[uint32]float64 {
 		var sources int
 		for _, source := range c.fiatRateSources {
 			rateInfo := source.assetRate(assetID)
-			if rateInfo != nil && time.Since(rateInfo.lastUpdate) < fiatRateDataExpiry {
+			if rateInfo != nil && time.Since(rateInfo.lastUpdate) < fiatRateDataExpiry && rateInfo.rate > 0 {
 				sources++
 				rateSum += rateInfo.rate
 			}

client/core/exchangeratefetcher.go

@@ -20,7 +20,7 @@ const (
 	// DefaultFiatCurrency is the currency for displaying assets fiat value.
 	DefaultFiatCurrency = "USD"
 	// fiatRateRequestInterval is the amount of time between calls to the exchange API.
-	fiatRateRequestInterval = 5 * time.Minute
+	fiatRateRequestInterval = 8 * time.Minute
 	// fiatRateDataExpiry : Any data older than fiatRateDataExpiry will be discarded.
 	fiatRateDataExpiry = 60 * time.Minute
 
@@ -96,6 +96,9 @@ func (source *commonRateSource) refreshRates(ctx context.Context, logger dex.Log
 	source.mtx.Lock()
 	defer source.mtx.Unlock()
 	for assetID, fiatRate := range fiatRates {
+		if fiatRate <= 0 {
+			continue
+		}
 		source.fiatRates[assetID] = &fiatRateInfo{
 			rate:       fiatRate,
 			lastUpdate: now,
@@ -148,6 +151,11 @@ func fetchCoinpaprikaRates(ctx context.Context, log dex.Logger, assets map[uint3
 		}
 		defer resp.Body.Close()
 
+		if resp.StatusCode != http.StatusOK {
+			log.Errorf("unexpected response, got status code %d", resp.StatusCode)
+			continue
+		}
+
 		// Read the raw bytes and close the response.
 		reader := io.LimitReader(resp.Body, 1<<20)
 		err = json.NewDecoder(reader).Decode(res)
@@ -191,6 +199,10 @@ func fetchDcrdataRates(ctx context.Context, log dex.Logger, assets map[uint32]*S
 	}
 	defer resp.Body.Close()
 
+	if resp.StatusCode != http.StatusOK {
+		log.Errorf("unexpected response, got status code %d", resp.StatusCode)
+		return nil
+	}
 	// Read the raw bytes and close the response.
 	reader := io.LimitReader(resp.Body, 1<<20)
 	err = json.NewDecoder(reader).Decode(res)
@@ -244,6 +256,11 @@ func fetchMessariRates(ctx context.Context, log dex.Logger, assets map[uint32]*S
 		}
 		defer resp.Body.Close()
 
+		if resp.StatusCode != http.StatusOK {
+			log.Errorf("unexpected response, got status code %d", resp.StatusCode)
+			continue
+		}
+
 		// Read the raw bytes and close the response.
 		reader := io.LimitReader(resp.Body, 1<<20)
 		err = json.NewDecoder(reader).Decode(res)