How export Custom Counters + NodeSDK

[priscofarina]

Hi guys,
I am looking for some examples but I did not get how to make the export of a single counter plus the ones already available through the auto-instrumentations-node :

/**
 * Autoinstrument node.js express app and export to prometheus
 */
const api = require('@opentelemetry/api');
const opentelemetry = require('@opentelemetry/sdk-node');
const { PrometheusExporter } = require('@opentelemetry/exporter-prometheus');
const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node');
const { MeterProvider }  = require('@opentelemetry/sdk-metrics');
const options = {port: 3001, startServer: true};
const prometheusExporter = new PrometheusExporter(options);

const meter = new MeterProvider({
  exporter: prometheusExporter,
  interval: 1000,
}).getMeter('Custom Metrics');

// Now, start recording data
const counter = meter.createCounter('mymetric', {
  description: 'Example of a counter'
});
counter.add(10);

const sdk = new opentelemetry.NodeSDK({
  // Optional - If omitted, the metrics SDK will not be initialized
  metricReader: prometheusExporter,

  // Optional - you can use the metapackage or load each instrumentation individually
  instrumentations: [getNodeAutoInstrumentations()],

  // See the Configuration section below for additional  configuration options
});

sdk.start().then(() => {
  // Resources have been detected and SDK is started
  console.log('>>>> OpenTelemetry SDK started');
});

process.on("SIGTERM", () => {
  sdk
    .shutdown()
    .then(
      () => console.log('>>>> SDK shut down successfully'),
      (err) => console.log('>>>> Error shutting down SDK', err)
    )
    .finally(() => process.exit(0));
});

Could you help me to get how to add my simple counter to the others:

From /metrics I see others but I am not able to see the single one.
If I follow this example:
https://www.npmjs.com/package/@opentelemetry/exporter-prometheus

I got that Error: MetricReader can not be bound to a MeterProvider again

# HELP target_info Target metadata
# TYPE target_info gauge
target_info{process_pid="49643",process_executable_name="node",process_command="/Users/priscofarina/open-telemetry/mock-server.js",process_command_line="/Users/priscofarina/.nvm/versions/node/v16.13.2/bin/node /Users/priscofarina/open-telemetry/mock-server.js",process_runtime_version="16.13.2",process_runtime_name="nodejs",process_runtime_description="Node.js"} 1
# HELP http_server_duration measures the duration of the inbound HTTP requests
# UNIT http_server_duration ms
# TYPE http_server_duration histogram
http_server_duration_count{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464"} 39 1673464020516
http_server_duration_sum{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464"} 64 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="0"} 0 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="5"} 38 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="10"} 38 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="25"} 39 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="50"} 39 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="75"} 39 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="100"} 39 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="250"} 39 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="500"} 39 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="1000"} 39 1673464020516
http_server_duration_bucket{http_scheme="http",http_method="GET",net_host_name="localhost",http_flavor="1.1",http_status_code="200",net_host_port="9464",le="+Inf"} 39 1673464020516
# HELP http_client_duration measures the duration of the outbound HTTP requests
# UNIT http_client_duration ms
# TYPE http_client_duration histogram
http_client_duration_count{http_method="POST",net_peer_name="localhost"} 1 1673464020516
http_client_duration_sum{http_method="POST",net_peer_name="localhost"} 7 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="0"} 0 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="5"} 0 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="10"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="25"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="50"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="75"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="100"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="250"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="500"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="1000"} 1 1673464020516
http_client_duration_bucket{http_method="POST",net_peer_name="localhost",le="+Inf"} 1 1673464020516

Thank you for your help

[priscofarina]

my mistake, those need to be defined once the sdk is started :-)