TelemetryClient keeps handles open

When running some code in a test using the TelemetryClient, Jest detects open handles.

Here’s a basic replication which causes the issue.

describe('telemetry', () => {
  // Requires the APPINSIGHTS_INSTRUMENTATIONKEY environment variable to be set
  test('replicate', async () => {
    const telemetryClient = new TelemetryClient()

    telemetryClient.trackMetric({ name: 'some_metric', value: 2 })

    // Wait for all logs to flush
    await new Promise((resolve) => {
      telemetryClient.flush({ callback: resolve })
    })
  })
})

If run using the --detectOpenHandles flag, the following error will be thrown.

Jest has detected the following 3 open handles potentially keeping Jest from exiting:

●  TCPWRAP

      42 |   // Requires the APPINSIGHTS_INSTRUMENTATIONKEY environment variable to be set
      43 |   test('replicate', async () => {
    > 44 |     const telemetryClient = new TelemetryClient()
         |                             ^
      45 |
      46 |     telemetryClient.trackMetric({ name: 'some_metric', value: 2 })
      47 |

      at Function.Object.<anonymous>.Util.makeRequest (../../node_modules/applicationinsights/Library/Util.ts:371:25)
      at Function.Object.<anonymous>.AzureVirtualMachine.getAzureComputeMetadata (../../node_modules/applicationinsights/Library/AzureVirtualMachine.ts:34:26)
      at ../../node_modules/applicationinsights/AutoCollection/Statsbeat.ts:332:44
      at Statsbeat.Object.<anonymous>.Statsbeat._getResourceProvider (../../node_modules/applicationinsights/AutoCollection/Statsbeat.ts:313:16)
      at Statsbeat.<anonymous> (../../node_modules/applicationinsights/AutoCollection/Statsbeat.ts:183:24)
      at step (../../node_modules/applicationinsights/out/AutoCollection/Statsbeat.js:33:23)
      at Object.next (../../node_modules/applicationinsights/out/AutoCollection/Statsbeat.js:14:53)
      at ../../node_modules/applicationinsights/out/AutoCollection/Statsbeat.js:8:71
      at Object.<anonymous>.__awaiter (../../node_modules/applicationinsights/out/AutoCollection/Statsbeat.js:4:12)
      at Statsbeat.Object.<anonymous>.Statsbeat.trackLongIntervalStatsbeats (../../node_modules/applicationinsights/out/AutoCollection/Statsbeat.js:190:16)
      at Statsbeat.Object.<anonymous>.Statsbeat.enable (../../node_modules/applicationinsights/AutoCollection/Statsbeat.ts:75:22)
      at NodeClient.TelemetryClient (../../node_modules/applicationinsights/Library/TelemetryClient.ts:50:29)
      at new NodeClient (../../node_modules/applicationinsights/out/Library/NodeClient.js:28:42)
      at Object.<anonymous> (tests/logging.test.ts:44:29)


  ●  TLSWRAP

      42 |   // Requires the APPINSIGHTS_INSTRUMENTATIONKEY environment variable to be set
      43 |   test('replicate', async () => {
    > 44 |     const telemetryClient = new TelemetryClient()
         |                             ^
      45 |
      46 |     telemetryClient.trackMetric({ name: 'some_metric', value: 2 })
      47 |

      at Function.Object.<anonymous>.CorrelationIdManager.queryCorrelationId (../../node_modules/applicationinsights/Library/CorrelationIdManager.ts:99:9)
      at Config.set (../../node_modules/applicationinsights/Library/Config.ts:115:30)
      at new Config (../../node_modules/applicationinsights/Library/Config.ts:103:34)
      at NodeClient.TelemetryClient (../../node_modules/applicationinsights/Library/TelemetryClient.ts:43:22)
      at new NodeClient (../../node_modules/applicationinsights/out/Library/NodeClient.js:28:42)
      at Object.<anonymous> (tests/logging.test.ts:44:29)


  ●  TLSWRAP

      42 |   // Requires the APPINSIGHTS_INSTRUMENTATIONKEY environment variable to be set
      43 |   test('replicate', async () => {
    > 44 |     const telemetryClient = new TelemetryClient()
         |                             ^
      45 |
      46 |     telemetryClient.trackMetric({ name: 'some_metric', value: 2 })
      47 |

      at Function.Object.<anonymous>.CorrelationIdManager.queryCorrelationId (../../node_modules/applicationinsights/Library/CorrelationIdManager.ts:99:9)
      at Config.set (../../node_modules/applicationinsights/Library/Config.ts:115:30)
      at new Config (../../node_modules/applicationinsights/Library/Config.ts:103:34)
      at new Statsbeat (../../node_modules/applicationinsights/AutoCollection/Statsbeat.ts:55:33)
      at NodeClient.TelemetryClient (../../node_modules/applicationinsights/Library/TelemetryClient.ts:49:31)
      at new NodeClient (../../node_modules/applicationinsights/out/Library/NodeClient.js:28:42)
      at Object.<anonymous> (tests/logging.test.ts:44:29)

I assumed this had to do with the use of a https.Agent internally and tried to specify one without any keep alive, but that didn’t help.

const telemetryClient = new TelemetryClient()
telemetryClient.config.httpsAgent = new https.Agent({ keepAlive: false })

I also tried to call the dispose function from the package, but as suspected that didn’t help. I assume it’s only applicable when using the default client and appInsights.setup().

Is there any way to cleanly dispose of a TelemetryClient?

[hectorhdzg]

We could add a shutdown functionality in the TelemeryClient that actually wait for these requests, allowing you to wait for it on your tests, let me know if this will work for everyone, @alexg-axis, @jonthysell

[rcbevans]

I was able to mitigate this by wrapping appInsights initialization in an env check, and then exporting the defaultClient from the module as TelemetryClient | undefined.

Setting all the options for automatic dependency collection etc to false didn’t prevent the handle being opened.

I was hoping appInsights.dispose() would have cleaned up sufficiently.