Here is my error log from my node js API web service on render, it first gets connected and later throws this huge log of error messages.
Jun 6 12:58:51 AM server running on port 4500
Jun 6 12:58:54 AM connected to database
Jun 6 12:59:18 AM /opt/render/project/src/node_modules/mongodb/lib/sdam/topology.js:278
Jun 6 12:59:18 AM const timeoutError = new error_1.MongoServerSelectionError(`Server selection timed out after ${serverSelectionTimeoutMS} ms`, this.description);
Jun 6 12:59:18 AM ^
Jun 6 12:59:18 AM
Jun 6 12:59:18 AM MongoServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
Jun 6 12:59:18 AM at Timeout._onTimeout (/opt/render/project/src/node_modules/mongodb/lib/sdam/topology.js:278:38)
Jun 6 12:59:18 AM at listOnTimeout (node:internal/timers:557:17)
Jun 6 12:59:18 AM at processTimers (node:internal/timers:500:7) {
Jun 6 12:59:18 AM reason: TopologyDescription {
Jun 6 12:59:18 AM type: 'Unknown',
Jun 6 12:59:18 AM servers: Map(1) {
Jun 6 12:59:18 AM 'localhost:27017' => ServerDescription {
Jun 6 12:59:18 AM address: 'localhost:27017',
Jun 6 12:59:18 AM type: 'Unknown',
Jun 6 12:59:18 AM hosts: [],
Jun 6 12:59:18 AM passives: [],
Jun 6 12:59:18 AM arbiters: [],
Jun 6 12:59:18 AM tags: {},
Jun 6 12:59:18 AM minWireVersion: 0,
Jun 6 12:59:18 AM maxWireVersion: 0,
Jun 6 12:59:18 AM roundTripTime: -1,
Jun 6 12:59:18 AM lastUpdateTime: 483067822,
Jun 6 12:59:18 AM lastWriteDate: 0,
Jun 6 12:59:18 AM error: MongoNetworkError: connect ECONNREFUSED 127.0.0.1:27017
Jun 6 12:59:18 AM at connectionFailureError (/opt/render/project/src/node_modules/mongodb/lib/cmap/connect.js:370:20)
Jun 6 12:59:18 AM at Socket.<anonymous> (/opt/render/project/src/node_modules/mongodb/lib/cmap/connect.js:293:22)
Jun 6 12:59:18 AM at Object.onceWrapper (node:events:510:26)
Jun 6 12:59:18 AM at Socket.emit (node:events:390:28)
Jun 6 12:59:18 AM at emitErrorNT (node:internal/streams/destroy:157:8)
Jun 6 12:59:18 AM at emitErrorCloseNT (node:internal/streams/destroy:122:3)
Jun 6 12:59:18 AM at processTicksAndRejections (node:internal/process/task_queues:83:21) {
Jun 6 12:59:18 AM cause: Error: connect ECONNREFUSED 127.0.0.1:27017
Jun 6 12:59:18 AM at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1161:16) {
Jun 6 12:59:18 AM errno: -111,
Jun 6 12:59:18 AM code: 'ECONNREFUSED',
Jun 6 12:59:18 AM syscall: 'connect',
Jun 6 12:59:18 AM address: '127.0.0.1',
Jun 6 12:59:18 AM port: 27017
Jun 6 12:59:18 AM },
Jun 6 12:59:18 AM [Symbol(errorLabels)]: Set(1) { 'ResetPool' }
Jun 6 12:59:18 AM },
Jun 6 12:59:18 AM topologyVersion: null,
Jun 6 12:59:18 AM setName: null,
Jun 6 12:59:18 AM setVersion: null,
Jun 6 12:59:18 AM electionId: null,
Jun 6 12:59:18 AM logicalSessionTimeoutMinutes: null,
Jun 6 12:59:18 AM primary: null,
Jun 6 12:59:18 AM me: null,
Jun 6 12:59:18 AM '$clusterTime': null
Jun 6 12:59:18 AM }
Jun 6 12:59:18 AM },
Jun 6 12:59:18 AM stale: false,
Jun 6 12:59:18 AM compatible: true,
Jun 6 12:59:18 AM heartbeatFrequencyMS: 10000,
Jun 6 12:59:18 AM localThresholdMS: 15,
Jun 6 12:59:18 AM setName: null,
Jun 6 12:59:18 AM maxElectionId: null,
Jun 6 12:59:18 AM maxSetVersion: null,
Jun 6 12:59:18 AM commonWireVersion: 0,
Jun 6 12:59:18 AM logicalSessionTimeoutMinutes: null
Jun 6 12:59:18 AM },
Jun 6 12:59:18 AM code: undefined,
Jun 6 12:59:18 AM [Symbol(errorLabels)]: Set(0) {}
Jun 6 12:59:18 AM }