Profiler Auto instrumentation

The agent can automatically instrument .NET Framework, .NET Core, and .NET applications using the .NET CLR Profiling APIs. The Profiling APIs provide a way to instrument an application or dependency code without code changes.

This approach works with the following

* Due to binding issues introduced by Microsoft, we recommend at least .NET Framework 4.7.2 for best compatibility.

** Minimum GLIBC version 2.14.

It instruments the following assemblies:

The general steps in configuring profiler auto instrumentation are as follows; See Instrumenting containers and services for configuration for common deployment environments.

Ensure you start your application in a context where the set environment variables are visible.

With this setup, the .NET runtime loads Elastic’s CLR profiler into the .NET process, which loads and instantiates the APM agent early in application startup. The profiler monitors methods of interest and injects code to instrument their execution.

Using global environment variables causes profiler auto instrumentation to be loaded for any .NET process started on the host. Often, the environment variables should be set only for specific services or containers. The following sections demonstrate how to configure common containers and services.

A build image containing the files for profiler auto instrumentation can be used as part of a multi-stage build

ARG AGENT_VERSION=<VERSION> 

FROM alpine:latest AS build
ARG AGENT_VERSION
WORKDIR /source

# install unzip
RUN apk update && apk add zip curl

# pull down the zip file based on ${AGENT_VERSION} ARG and unzip
RUN curl -L -o elastic_apm_profiler_${AGENT_VERSION}.zip https://github.com/elastic/apm-agent-dotnet/releases/download/v${AGENT_VERSION}/elastic_apm_profiler_${AGENT_VERSION}.zip && \
    unzip elastic_apm_profiler_${AGENT_VERSION}.zip -d /elastic_apm_profiler_${AGENT_VERSION}

The files can then be copied into a subsequent stage

COPY --from=build /elastic_apm_profiler_${AGENT_VERSION} /elastic_apm_profiler

Environment variables can be added to a Dockerfile to configure profiler auto instrumentation

ENV CORECLR_ENABLE_PROFILING=1
ENV CORECLR_PROFILER={FA65FE15-F085-4681-9B20-95E04F6C03CC}
ENV CORECLR_PROFILER_PATH=/elastic_apm_profiler/libelastic_apm_profiler.so
ENV ELASTIC_APM_PROFILER_HOME=/elastic_apm_profiler
ENV ELASTIC_APM_PROFILER_INTEGRATIONS=/elastic_apm_profiler/integrations.yml

ENTRYPOINT ["dotnet", "your-application.dll"]

Environment variables can be added to specific Windows services by adding an entry to the Windows registry. Using PowerShell

.NET Framework service.

$environment = [string[]]@(
  "COR_ENABLE_PROFILING=1",
  "COR_PROFILER={FA65FE15-F085-4681-9B20-95E04F6C03CC}",
  "COR_PROFILER_PATH=<unzipped directory>\elastic_apm_profiler.dll",
  "ELASTIC_APM_PROFILER_HOME=<unzipped directory>",
  "ELASTIC_APM_PROFILER_INTEGRATIONS=<unzipped directory>\integrations.yml"
  "ELASTIC_APM_SERVER_URL=<apm server url>"
  "ELASTIC_APM_SECRET_TOKEN=<secret token>")

Set-ItemProperty HKLM:SYSTEM\CurrentControlSet\Services\<service-name> -Name Environment -Value $environment

.NET Core service.

$environment = [string[]]@(
  "CORECLR_ENABLE_PROFILING=1",
  "CORECLR_PROFILER={FA65FE15-F085-4681-9B20-95E04F6C03CC}",
  "CORECLR_PROFILER_PATH=<unzipped directory>\elastic_apm_profiler.dll", 
  "ELASTIC_APM_PROFILER_HOME=<unzipped directory>",
  "ELASTIC_APM_PROFILER_INTEGRATIONS=<unzipped directory>\integrations.yml"
  "ELASTIC_APM_SERVER_URL=<apm server url>" 
  "ELASTIC_APM_SECRET_TOKEN=<secret token>") 

Set-ItemProperty HKLM:SYSTEM\CurrentControlSet\Services\<service-name> -Name Environment -Value $environment 

The service must then be restarted for the change to take effect. With PowerShell

Restart-Service <service-name>

For IIS versions before IIS 10, it is not possible to set environment variables scoped to a specific application pool, so environment variables need to set globally.

For IIS 10 onwards, environment variables can be set for an application pool using AppCmd.exe. With PowerShell

.NET Framework.

$appcmd = "$($env:systemroot)\system32\inetsrv\AppCmd.exe"
$appPool = "<application-pool>" 
$profilerHomeDir = "<unzipped directory>" 
$environment = @{
  COR_ENABLE_PROFILING = "1"
  COR_PROFILER = "{FA65FE15-F085-4681-9B20-95E04F6C03CC}"
  COR_PROFILER_PATH = "$profilerHomeDir\elastic_apm_profiler.dll"
  ELASTIC_APM_PROFILER_HOME = "$profilerHomeDir"
  ELASTIC_APM_PROFILER_INTEGRATIONS = "$profilerHomeDir\integrations.yml"
  COMPlus_LoaderOptimization = "1" 
  ELASTIC_APM_SERVER_URL = "<apm server url>" 
  ELASTIC_APM_SECRET_TOKEN = "<secret token>" 
}

$environment.Keys | ForEach-Object {
  & $appcmd set config -section:system.applicationHost/applicationPools /+"[name='$appPool'].environmentVariables.[name='$_',value='$($environment[$_])']"
}

.NET Core.

$appcmd = "$($env:systemroot)\system32\inetsrv\AppCmd.exe"
$appPool = "<application-pool>" 
$profilerHomeDir = "<unzipped directory>" 
$environment = @{
  CORECLR_ENABLE_PROFILING = "1"
  CORECLR_PROFILER = "{FA65FE15-F085-4681-9B20-95E04F6C03CC}"
  CORECLR_PROFILER_PATH = "$profilerHomeDir\elastic_apm_profiler.dll"
  ELASTIC_APM_PROFILER_HOME = "$profilerHomeDir"
  ELASTIC_APM_PROFILER_INTEGRATIONS = "$profilerHomeDir\integrations.yml"
  ELASTIC_APM_SERVER_URL = "<apm server url>" 
  ELASTIC_APM_SECRET_TOKEN = "<secret token>" 
}

$environment.Keys | ForEach-Object {
  & $appcmd set config -section:system.applicationHost/applicationPools /+"[name='$appPool'].environmentVariables.[name='$_',value='$($environment[$_])']"
}

Once environment variables have been set, stop and start IIS so that applications hosted in IIS will see the new environment variables.

net stop /y was
net start w3svc

Environment variables can be added to specific services run with systemd by creating an environment.env file containing the following

CORECLR_ENABLE_PROFILING=1
CORECLR_PROFILER={FA65FE15-F085-4681-9B20-95E04F6C03CC}
CORECLR_PROFILER_PATH=/<unzipped directory>/libelastic_apm_profiler.so 
ELASTIC_APM_PROFILER_HOME=/<unzipped directory>
ELASTIC_APM_PROFILER_INTEGRATIONS=/<unzipped directory>/integrations.yml
ELASTIC_APM_SERVER_URL=<apm server url> 
ELASTIC_APM_SECRET_TOKEN=<secret token> 

Then adding an EnvironmentFile entry to the service’s configuration file that references the path to the environment.env file

[Service]
EnvironmentFile=/path/to/environment.env
ExecStart=<command> 

After adding the EnvironmentFile entry, restart the service.

systemctl reload-or-restart <service>

The profiler auto instrumentation has its own set of environment variables to manage the instrumentation. These are used in addition to agent configuration through environment variables.

The following processes are *always* excluded from profiling by default.

The following service names are *always* excluded from profiling by default.

The default value is warn. More verbose log levels like trace and debug can affect the runtime performance of profiler auto instrumentation, so are recommended only for diagnostics purposes.

This takes precedence over the now deprecated ELASTIC_APM_PROFILER_LOG

If the default directory cannot be written to for some reason, the profiler will try to write log files to a logs directory in the home directory specified by ELASTIC_APM_PROFILER_HOME environment variable.

This takes precedence over the now deprecated ELASTIC_APM_PROFILER_LOG_DIR

The default value is file, which logs to the directory specified by ELASTIC_APM_PROFILER_LOG_DIR environment variable.

This takes precedence over the now deprecated ELASTIC_APM_PROFILER_LOG_TARGETS