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Tomcat OpenTelemetry Instrumentation

This document contains instructions on how to set up OpenTelemetry instrumentation in your Tomcat applications. OpenTelemetry, also known as OTel for short, is an open source observability framework that can help you generate and collect telemetry data - traces, metrics, and logs from your Tomcat application.

OpenTelemetry Java is the language-specific implementation of OpenTelemetry in Java that can be used to instrument Tomcat applications.

Once the telemetry data is collected, you can configure an exporter to send the data to SigNoz.

There are three major steps to using OpenTelemetry:

  • Instrumenting your Tomcat application with OpenTelemetry
  • Configuring exporter to send data to SigNoz
  • Validating that configuration to ensure that data is being sent as expected.
OpenTelemetry helps to generate and collect telemetry data from your application which is then sent to an observability backend like SigNoz
OpenTelemetry helps generate and collect telemetry data from Tomcat applications which can then be sent to SigNoz for storage, visualization, and analysis.

There are two types of application instrumentation:

  • Auto Instrumentation
    A completely automatic and out of box experience, with minimal code changes. For your Tomcat application, we recommend getting started with auto instrumentation.

  • Manual Instrumentation
    It involves writing instrumentation using OpenTelemetry SDK and API manually. You would need to get a handle to an instance of the OpenTelemetry interface, acquire a tracer, and create spans manually.

Let’s understand how to download, install, and run OpenTelemetry in a Tomcat application.

Requirements​

Java 8 or higher

Send Traces to SigNoz Cloud​

OpenTelemetry provides a handy Java JAR agent that can be attached to any Java 8+ application and dynamically injects bytecode to capture telemetry from a number of popular libraries and frameworks.

Based on your application environment, you can choose the setup below to send traces to SigNoz Cloud.

From VMs, there are two ways to send data to SigNoz Cloud.

Send traces directly to SigNoz Cloud​

OpenTelemetry Java agent can send traces directly to SigNoz Cloud.

Step 1. Download otel java binary agent

wget https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/latest/download/opentelemetry-javaagent.jar

Step 2. Enable the instrumentation agent and run your application

If you run your .war package by putting in webapps folder, just add setenv.sh in your Tomcat bin folder.

This should set these environment variables and start sending telemetry data to SigNoz Cloud.

export CATALINA_OPTS="$CATALINA_OPTS -javaagent:/path/to/opentelemetry-javaagent.jar"
export OTEL_EXPORTER_OTLP_HEADERS="signoz-access-token=SIGNOZ_INGESTION_KEY"
export OTEL_EXPORTER_OTLP_ENDPOINT=https://ingest.{region}.signoz.cloud:443
export OTEL_RESOURCE_ATTRIBUTES=service.name=<app_name>
  • <app_name> is the name for your application
  • SIGNOZ_INGESTION_KEY is the API token provided by SigNoz. You can find your ingestion key from SigNoz cloud account details sent on your email.

Depending on the choice of your region for SigNoz cloud, the ingest endpoint will vary according to this table.

RegionEndpoint
USingest.us.signoz.cloud:443
INingest.in.signoz.cloud:443
EUingest.eu.signoz.cloud:443

In case you encounter an issue where all applications do not get listed in the services section then please refer to the troubleshooting section.

Send traces via OTel Collector binary​

OTel Collector binary helps to collect logs, hostmetrics, resource and infra attributes. It is recommended to install Otel Collector binary to collect and send traces to SigNoz cloud. You can correlate signals and have rich contextual data through this way.

You can find instructions to install OTel Collector binary here in your VM. Once you are done setting up your OTel Collector binary, you can follow the below steps for instrumenting your Java application.

Step 1. Download OTel java binary agent

wget https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/latest/download/opentelemetry-javaagent.jar

Step 2. Enable the instrumentation agent and run your application

If you run your .war package by putting in webapps folder, just add setenv.sh in your Tomcat bin folder.

This should set these environment variables and start sending telemetry data to SigNoz Cloud.

export CATALINA_OPTS="$CATALINA_OPTS -javaagent:/path/to/opentelemetry-javaagent.jar"
  • path/to - Update it to the path of your downloaded Java JAR agent.

In case you encounter an issue where all applications do not get listed in the services section then please refer to the troubleshooting section.

Send Traces to Self-Hosted SigNoz​

You can use OpenTelemetry Java to send your traces directly to SigNoz. OpenTelemetry provides a handy Java JAR agent that can be attached to any Java 8+ application and dynamically injects bytecode to capture telemetry from a number of popular libraries and frameworks.

Steps to auto-instrument Tomcat applications for traces​

OpenTelemetry Java auto-instrumentation supports collecting telemetry data from a huge number of libraries and frameworks. You can check out the full list here.

  1. Download the latest OpenTelemetry Java JAR agent
    Download the latest Java JAR agent. You can also use the terminal to get the file using the following command:

     wget https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/latest/download/opentelemetry-javaagent.jar

  1. Enable the instrumentation agent and run your application
    If you run your .war package by putting in webapps folder, just add setenv.sh in your Tomcat bin folder.

    This should set these environment variables and start sending telemetry data to SigNoz backend specified in the IP

    export CATALINA_OPTS="$CATALINA_OPTS -javaagent:/path/to/opentelemetry-javaagent.jar"
    export OTEL_EXPORTER_OTLP_ENDPOINT=http://<IP of SigNoz Backend>:4317
    export OTEL_RESOURCE_ATTRIBUTES=service.name=<app_name>

    where app_name is the name you want to set for your application and IP of SigNoz Backend is the IP where SigNoz backend is accessible.

With the above environment variables, we are configuring the exporter to send data to SigNoz backend. By default, OpenTelemetry Java agent uses OTLP exporter configured to send data.

Two things to note about the environment variables:

OTEL_EXPORTER_OTLP_ENDPOINT - This is the endpoint of the machine where SigNoz is installed.

path/to - Update it to the path of your downloaded Java JAR agent.

If you have installed SigNoz on a machine with IP http://40.76.59.122 and your Java JAR agent is saved at /Users/john/Downloads/, then the final command looks like:

export CATALINA_OPTS="$CATALINA_OPTS -javaagent:/Users/john/Downloads/opentelemetry-javaagent.jar"
export OTEL_EXPORTER_OTLP_ENDPOINT=http://40.76.59.122:4317
export OTEL_RESOURCE_ATTRIBUTES=service.name=Tomcat-SigNoz

Here’s a handy grid to figure out which address to use to send data to SigNoz.

note

💡 Remember to allow incoming requests to port 4317 of the machine where SigNoz backend is hosted.

Here's a video on how to instrument Tomcat applications with SigNoz and a blog with step by step instructions.

 

YouTube's thumbnail image for the video.

 

In case you encounter an issue where all applications do not get listed in the services section then please refer to the troubleshooting section.

Validating instrumentation by checking for traces​

With your application running, you can verify that you’ve instrumented your application with OpenTelemetry correctly by confirming that tracing data is being reported to SigNoz.

To do this, you need to ensure that your application generates some data. Applications will not produce traces unless they are being interacted with, and OpenTelemetry will often buffer data before sending. So you need to interact with your application and wait for some time to see your tracing data in SigNoz.

Validate your traces in SigNoz:

  1. Trigger an action in your app that generates a web request. Hit the endpoint a number of times to generate some data. Then, wait for some time.
  2. In SigNoz, open the Services tab. Hit the Refresh button on the top right corner, and your application should appear in the list of Applications.
  3. Go to the Traces tab, and apply relevant filters to see your application’s traces.

You might see other dummy applications if you’re using SigNoz for the first time. You can remove it by following the docs here.

Java Application in the list of services being monitored in SigNoz
Java Application in the list of services being monitored in SigNoz

Configuring the agent​

The agent is highly configurable. You can check out all the configuration options available here.

Disabled instrumentations​

Some instrumentations can produce too many spans and make traces very noisy. For this reason, the following instrumentations are disabled by default:

  • jdbc-datasource which creates spans whenever the java.sql.DataSource#getConnection method is called.
  • dropwizard-metrics, which might create very low-quality metrics data because of the lack of label/attribute support in the Dropwizard metrics API.

To enable them, add the otel.instrumentation.<name>.enabled system property: -Dotel.instrumentation.jdbc-datasource.enabled=true

Manual Instrumentation​

For manual instrumentation of Java application, refer to the docs here.

Troubleshooting your installation​

If spans are not being reported to SigNoz, try running in debug mode by setting OTEL_LOG_LEVEL=debug:

The debug log level will print out the configuration information. It will also emit every span to the console, which should look something like:


Span {
  attributes: {},
  links: [],
  events: [],
  status: { code: 0 },
  endTime: [ 1597810686, 885498645 ],
  _ended: true,
  _duration: [ 0, 43333 ],
  name: 'bar',
  spanContext: {
    traceId: 'eca3cc297720bd705e734f4941bca45a',
    spanId: '891016e5f8c134ad',
    traceFlags: 1,
    traceState: undefined
  },
  parentSpanId: 'cff3a2c6bfd4bbef',
  kind: 0,
  startTime: [ 1597810686, 885455312 ],
  resource: Resource { labels: [Object] },
  instrumentationLibrary: { name: 'example', version: '*' },
  _logger: ConsoleLogger {
    debug: [Function],
    info: [Function],
    warn: [Function],
    error: [Function]
  },
  _traceParams: {
    numberOfAttributesPerSpan: 32,
    numberOfLinksPerSpan: 32,
    numberOfEventsPerSpan: 128
  },
  _spanProcessor: MultiSpanProcessor { _spanProcessors: [Array] }
},

 

Sample Java Application​

Frequently Asked Questions​

  1. How to find what to use in IP of SigNoz if I have installed SigNoz in Kubernetes cluster?

    Based on where you have installed your application and where you have installed SigNoz, you need to find the right value for this. Please use this grid to find the value you should use for IP of SigNoz

  2. I am sending data from my application to SigNoz, but I don't see any events or graphs in the SigNoz dashboard. What should I do?

    This could be because of one of the following reasons:

    1. Your application is generating telemetry data, but not able to connect with SigNoz installation

      Please use this troubleshooting guide to find if your application is able to access SigNoz installation and send data to it.

    2. Your application is not actually generating telemetry data

      Please check if the application is generating telemetry data first. You can use Console Exporter to just print your telemetry data in console first. Join our Slack Community if you need help on how to export your telemetry data in console

    3. Your SigNoz installation is not running or behind a firewall

      Please double check if the pods in SigNoz installation are running fine. docker ps or kubectl get pods -n platform are your friends for this.