balance.go

//  Copyright 2022 Blockdaemon Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"context"
	"time"

	"github.com/gagliardetto/solana-go"
	"github.com/gagliardetto/solana-go/rpc"
	"github.com/prometheus/client_golang/prometheus"
	"go.blockdaemon.com/pyth_exporter/metrics"
	"go.uber.org/zap"
)

// balanceScraper retrieves the Pyth publisher balances on request.
type balanceScraper struct {
	*prometheus.GaugeVec

	log        *zap.Logger
	rpc        *rpc.Client
	publishers []solana.PublicKey
}

func newBalanceScraper(publishers []solana.PublicKey, rpcURL string, log *zap.Logger) *balanceScraper {
	return &balanceScraper{
		GaugeVec:   metrics.PublisherBalances,
		rpc:        rpc.New(rpcURL),
		log:        log,
		publishers: publishers,
	}
}

// Collect gets invoked by the Prometheus exporter when a new scrape is requested.
func (b *balanceScraper) Collect(metrics chan<- prometheus.Metric) {
	const collectTimeout = 5 * time.Second
	ctx, cancel := context.WithTimeout(context.Background(), collectTimeout)
	defer cancel()
	b.update(ctx)
	b.GaugeVec.Collect(metrics)
}

func (b *balanceScraper) update(ctx context.Context) {
	res, err := b.rpc.GetMultipleAccounts(ctx, b.publishers...)
	if err != nil {
		b.log.Warn("Failed to check publisher SOL balances", zap.Error(err))
		return
	}
	for i, acc := range res.Value {
		var balance float64
		if acc != nil {
			balance = float64(acc.Lamports)
		}
		b.GaugeVec.
			WithLabelValues(b.publishers[i].String()).
			Set(balance)
	}
}