feat: Add prometheus gauge for total rfqm trade capacity (0xProject#755)

src/services/rfqm_service.ts

@@ -671,12 +671,19 @@ export class RfqmService {
     public async runHealthCheckAsync(): Promise<HealthCheckResult> {
         const heartbeats = await this._dbUtils.findRfqmWorkerHeartbeatsAsync();
         const registryBalance = await this._blockchainUtils.getAccountBalanceAsync(this._registryAddress);
+        let gasPrice: BigNumber | undefined;
+        try {
+            gasPrice = await this._protocolFeeUtils.getGasPriceEstimationOrThrowAsync();
+        } catch (error) {
+            logger.warn({ error }, 'Failed to get gas price for health check');
+        }
         return computeHealthCheckAsync(
             RFQM_MAINTENANCE_MODE,
             registryBalance,
             RFQM_MAKER_ASSET_OFFERINGS,
             this._sqsProducer,
             heartbeats,
+            gasPrice,
         );
     }
 

src/utils/rfqm_health_check.ts

@@ -1,9 +1,9 @@
 import { RfqMakerAssetOfferings } from '@0x/asset-swapper';
 import { BigNumber } from '@0x/utils';
-import { Counter } from 'prom-client';
+import { Counter, Gauge } from 'prom-client';
 import { Producer } from 'sqs-producer';
 
-import { ETH_DECIMALS } from '../constants';
+import { ETH_DECIMALS, RFQM_TX_GAS_ESTIMATE } from '../constants';
 import { RfqmWorkerHeartbeatEntity } from '../entities';
 
 const SQS_QUEUE_SIZE_DEGRADED_THRESHOLD = 10; // More messages sitting in queue than this will cause a DEGRADED issue
@@ -26,6 +26,11 @@ const RFQM_HEALTH_CHECK_ISSUE_COUNTER = new Counter({
     help: 'RFQM health system has detected a problem with the system',
 });
 
+const RFQM_TOTAL_SYSTEM_TRADE_CAPACITY_GAUGE = new Gauge({
+    name: 'rfqm_total_system_trade_capacity',
+    help: 'Total amount of ETH in the worker pool divided by the current expected gas of a trade',
+});
+
 export enum HealthCheckStatus {
     Operational = 'operational',
     Maintenance = 'maintenance',
@@ -81,6 +86,7 @@ export async function computeHealthCheckAsync(
     offerings: RfqMakerAssetOfferings,
     producer: Producer,
     heartbeats: RfqmWorkerHeartbeatEntity[],
+    gasPrice?: BigNumber,
 ): Promise<HealthCheckResult> {
     const pairs = transformPairs(offerings);
 
@@ -97,6 +103,14 @@ export async function computeHealthCheckAsync(
         RFQM_HEALTH_CHECK_ISSUE_COUNTER.labels(issue.status, issue.label).inc(),
     );
 
+    if (gasPrice) {
+        // Note that this gauge is an estimation of the total number of trades, since two workers could have
+        // 50% of the amount for one trade and the gauge would show 1 but the actual capacity would be 0.
+        const totalWorkerBalance = heartbeats.reduce((total, { balance }) => total.plus(balance), new BigNumber(0));
+        const totalSystemTradeCapacity = totalWorkerBalance.div(gasPrice.times(RFQM_TX_GAS_ESTIMATE));
+        RFQM_TOTAL_SYSTEM_TRADE_CAPACITY_GAUGE.set(totalSystemTradeCapacity.toNumber());
+    }
+
     return {
         status: getWorstStatus([httpStatus, workersStatus]),
         pairs,

test/services/rfqm_service_test.ts

@@ -1290,7 +1290,10 @@ describe('RfqmService', () => {
 
     describe('runHealthCheckAsync', () => {
         it('returns active pairs', async () => {
-            const service = buildRfqmServiceForUnitTest();
+            const dbUtilsMock = mock(RfqmDbUtils);
+            when(dbUtilsMock.findRfqmWorkerHeartbeatsAsync()).thenResolve([]);
+            const service = buildRfqmServiceForUnitTest({ dbUtils: instance(dbUtilsMock) });
+
             const result = await service.runHealthCheckAsync();
 
             expect(result.pairs).to.have.key(