# Tracer is null

**URL:** <https://discuss.elastic.co/t/tracer-is-null/362251>\
**Category:** APM\
**Tags:** dotnet\
**Created:** [June 30, 2024, 1:17pm UTC](https://discuss.elastic.co/t/tracer-is-null/362251 "2024-06-30T13:17:47Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![monty241](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/monty241/32/81681_2.png) [@monty241](https://discuss.elastic.co/u/monty241)\
**Post date:** [June 30, 2024, 1:17pm UTC](https://discuss.elastic.co/t/tracer-is-null/362251/1 "2024-06-30T13:17:47Z")

</div>

Based upon 1.27.0.0 of Elastic.Apm.NetCoreAll.

During initialization, `Tracer` is set to null on `agentComponents` after execution of own code called from Startup of website method `ConfigureServices(IServiceCollection services)`:

```auto
AgentComponents agentComponents = new AgentComponents(null, elasticApmConfig, null);

```

where `elasticApmConfig` is of a class implementing `IConfigurationReader`, with `Enabled` = true.

According to `Elastic.Apm.Agent.IsConfigured` being true, the configuration is correct.

## Reflection

The code of `AgentComponents` was checked. The constructor with 3 arguments seems to be forwarded to an internal constructor. After execution also other properties are null, such as `PayloadSender`, despite being initialized in the internal constructor as:

```auto
PayloadSender = payloadSender
				?? new PayloadSenderV2(Logger, ConfigurationStore.CurrentSnapshot, Service, system, ApmServerInfo, isEnabled: Configuration.Enabled, serverInfoCallback: ServerInfoCallback);

```

## Question

How can `Tracer` be initialized correctly?

---

<div class="post-metadata">

**Author:** ![monty241](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/monty241/32/81681_2.png) [@monty241](https://discuss.elastic.co/u/monty241)\
**Post date:** [July 1, 2024, 7:18am UTC](https://discuss.elastic.co/t/tracer-is-null/362251/2 "2024-07-01T07:18:37Z")

</div>

Problem strongly resembles [Object Reference after updating 1.8.1 -\> 1.9 (Elastic.Apm.Agent.Tracer is null) · Issue #1254 · elastic/apm-agent-dotnet · GitHub](https://github.com/elastic/apm-agent-dotnet/issues/1254).

AgentComponents has:

```auto
catch (Exception e)
{
   Logger.Error()?.LogException(e, "Failed initializing agent.");
}

```

which can be a No-Operation. The exception is for reasons described in the issue not re-raised, and with logger missing leads to an ignored exception.

In 1.9 it seems to have been `logger?.Error()?...`.

I will try to use a logger.

---

<div class="post-metadata">

**Author:** ![monty241](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/monty241/32/81681_2.png) [@monty241](https://discuss.elastic.co/u/monty241)\
**Post date:** [July 1, 2024, 8:00am UTC](https://discuss.elastic.co/t/tracer-is-null/362251/3 "2024-07-01T08:00:48Z")

</div>

With logger attached, the problem becomes clear, an unhandled NullReferenceException on constructor of PayloadSenderV2:

```auto
   at Elastic.Apm.Report.PayloadSenderV2..ctor(IApmLogger logger, IConfiguration configuration, Service service, System system, IApmServerInfo apmServerInfo, HttpMessageHandler httpMessageHandler, String dbgName, Boolean isEnabled, IEnvironmentVariables environmentVariables, Action`2 serverInfoCallback)
   at Elastic.Apm.AgentComponents..ctor(IApmLogger logger, IConfigurationReader configurationReader, IPayloadSender payloadSender, IMetricsCollector metricsCollector, ICurrentExecutionSegmentsContainer currentExecutionSegmentsContainer, ICentralConfigurationFetcher centralConfigurationFetcher, IApmServerInfo apmServerInfo, BreakdownMetricsProvider breakdownMetricsProvider)

```

The root cause is the following code:

```auto
var process = ProcessInformation.Create();
_metadata = new Metadata { Service = service, System = System, Process = process };
foreach (var globalLabelKeyValue in configuration.GlobalLabels)
	_metadata.Labels.Add(globalLabelKeyValue.Key, globalLabelKeyValue.Value);
_cachedActivationMethod = _metadata.Service?.Agent.ActivationMethod;
ResetActivationMethodIfKnownBrokenApmServer();

```

`GlobalLabels` is an undocumented entry in IConfigurationReader, and there is no clue whether it is nullable or not (the Elastic APM package does not yet use the new checks to avoid NullReferenceExceptions such as by

```xml

```

After changing the custom class implementing IConfigurationReader to use:

```auto
        [NSJ.JsonProperty("GlobalLabels")]
        [STJ.JsonPropertyName("GlobalLabels")]
        [ConfigurationKeyName("GlobalLabels")]
        public IReadOnlyDictionary<string, string> GlobalLabels { get; set; } = new Dictionary<string, string>();

```

the specific exception does not occur.

## Take aways

- Always add a logger, possibly with a crash on an error. The initialization of `AgentComponents` violates the Fail-Fast principle behind Ada.
- I was unable to find a sample implementation of IConfigurationReader and IApmLogger. Take your time to craft one nonetheless.

The maintainer might want to consider adding an `if` to the `foreach`, or using the new language features to avoid this type of error.