rotel 🌶️ 🍅

Node.js package for Rotel.

Description

This package provides an embedded lightweight agent that can collect OpenTelemetry data, built on Rotel. When started, it spawns a background daemon that accepts OpenTelemetry metrics, traces, and logs. Designed for minimal overhead, Rotel reduces resource consumption while simplifying telemetry collection and processing in Node.js applications—without requiring additional sidecar containers.

Telemetry Type	Support
Metrics	Alpha
Traces	Alpha
Logs	Alpha

How it works

By default, the Rotel agent listens for OpenTelemetry data over gRPC (port 4317) and HTTP (port 4318) on localhost. It efficiently batches telemetry signals and forwards them to a configurable OpenTelemetry protocol (OTLP) compatible endpoint.

In your application, you use the OpenTelemetry Javascript SDK to add instrumentation for traces, metrics, and logs. The SDK by default will communicate over ports 4317 or 4318 on localhost to the Rotel agent. You can now ship your instrumented application and efficiently export OpenTelemetry data to your vendor or observability tool of choice with a single deployment artifact.

Future updates will introduce support for filtering data, transforming telemetry, and exporting to different vendors and tools.

Getting started

Rotel configuration

Add the rotel npm package to your project's dependencies. There are two approaches to configuring rotel:

1. Typescript or Javascript
2. Environment variables

JS / TS config

In the startup section of your index.js or index.ts add the following code block. Replace the endpoint with the endpoint of your OpenTelemetry vendor and any required API KEY headers.

---

const{ Rotel,Config }=require("@streamfold/rotel");const{ Client }require("@streamfold/rotel/client");constrotel=newRotel({enabled: true,exporters: {"otlp" : Config.otlp_exporter({endpoint: "https://foo.example.com",headers: {"x-api-key": "xxxxx",},}),},exporters_traces: ["otlp"],exporters_metrics: ["otlp"],exporters_logs: ["otlp"],})rotel.start()

Environment variables

You can also configure rotel entirely with environment variables. In your application startup, insert:

const{ Rotel }=require("@streamfold/rotel");newRotel().start();

In your application deployment configuration, set the following environment variables. These match the typed configuration above:

• ROTEL_ENABLED=true
• ROTEL_EXPORTERS=otlp
• ROTEL_EXPORTER_OTLP_ENDPOINT=https://foo.example.com
• ROTEL_EXPORTER_OTLP_CUSTOM_HEADERS=x-api-key={API_KEY}
• ROTEL_EXPORTERS_TRACES=otlp
• ROTEL_EXPORTERS_METRICS=otlp
• ROTEL_EXPORTERS_LOGS=otlp

Any typed configuration options will override environment variables of the same name.

---

See the Configuration section for the full list of options.

OpenTelemetry SDK configuration

Once the Rotel agent is running, you may need to configure your application's instrumentation. If you are using the default rotel endpoints of localhost:4317 and localhost:4318, then you should not need to change anything.

To set the endpoint the OpenTelemetry SDK will use, set the following environment variable:

• OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317

Configuration

This is the full list of options and their environment variable alternatives. Any defaults left blank in the table are either False or None.

Option Name	Type	Environ	Default	Options
enabled	boolean	ROTEL_ENABLED
pid_file	string	ROTEL_PID_FILE	/tmp/rotel-agent.pid
log_file	string	ROTEL_LOG_FILE	/tmp/rotel-agent.log
log_format	string	ROTEL_LOG_FORMAT	text	json, text
debug_log	string[]	ROTEL_DEBUG_LOG		traces, metrics
otlp_grpc_endpoint	string	ROTEL_OTLP_GRPC_ENDPOINT	localhost:4317
otlp_http_endpoint	string	ROTEL_OTLP_HTTP_ENDPOINT	localhost:4318
otlp_receiver_traces_disabled	boolean	ROTEL_OTLP_RECEIVER_TRACES_DISABLED
otlp_receiver_metrics_disabled	boolean	ROTEL_OTLP_RECEIVER_METRICS_DISABLED
otlp_receiver_logs_disabled	boolean	ROTEL_OTLP_RECEIVER_LOGS_DISABLED
exporters	Map<string, Exporter>
exporters_traces	string[]	ROTEL_EXPORTERS_TRACES
exporters_metrics	string[]	ROTEL_EXPORTERS_METRICS
exporters_logs	string[]	ROTEL_EXPORTERS_LOGS

For each exporter you would like to use, see the configuration options below. Exporters should be assigned to the exporters object with a custom name.

OTLP Exporter

To construct an OTLP exporter, use the method Config.otlp_exporter() with the following options.

Option Name	Type	Default	Options
endpoint	string
protocol	string	grpc	grpc or http
headers	Map<string, string>
compression	string	gzip	gzip or none
request_timeout	string	5s
retry_initial_backoff	string	5s
retry_max_backoff	string	30s
retry_max_elapsed_time	string	300s
batch_max_size	number	8192
batch_timeout	string	200ms
tls_cert_file	string
tls_key_file	string
tls_ca_file	string
tls_skip_verify	boolean

Datadog Exporter

Rotel provides an experimental Datadog exporter that supports traces at the moment. Construct a Datadog exporter with the method Config.datadog_exporter() using the following options.

Option Name	Type	Default	Options
region	string	us1	us1, us3, us5, eu, ap1
custom_endpoint	string
api_key	string

ClickHouse Exporter

Rotel provides a ClickHouse exporter with support for metrics, logs, and traces. Construct a ClickHouse exporter with the method Config.clickhouse_exporter() using the following options.

Option Name	Type	Default	Options
endpoint	string
database	string	otel
table_prefix	string	otel
compression	string	lz4
async_insert	boolean	true
user	string
password	string
enable_json	boolean
json_underscore	boolean

Kafka Exporter

Rotel provides a Kafka exporter with support for metrics, logs, and traces. Construct a Kafka exporter with the method Config.kafka_exporter() using the following options.

Option Name	Type	Default	Options
brokers	string[]	localhost:9092
traces_topic	string	otlp_traces
logs_topic	string	otlp_logs
metrics_topic	string	otlp_metrics
format	string	protobuf	json, protobuf
compression	string	none	gzip, snappy, lz4, zstd, none
acks	string	one	all, one, none
client_id	string	rotel
max_message_bytes	number	1000000
linger_ms	number	5
retries	number	2147483647
retry_backoff_ms	number	100
retry_backoff_max_ms	number	1000
message_timeout_ms	number	300000
request_timeout_ms	number	30000
batch_size	number	1000000
partitioner	string	consistent-random	consistent, consistent-random, murmur2-random, murmur2, fnv1a, fnv1a-random
partition_metrics_by_resource_attributes	boolean
partition_logs_by_resource_attributes	boolean
custom_config	string
sasl_username	string
sasl_password	string
sasl_mechanism	string
security_protocol	string	PLAINTEXT	PLAINTEXT, SSL, SASL_PLAINTEXT, SASL_SSL

Blackhole Exporter

The Blackhole exporter is useful for testing purposes. It accepts telemetry data but does not forward it anywhere. Construct a Blackhole exporter with the method Config.blackhole_exporter(). This exporter has no configuration options.

Multiple Exporters

Rotel supports multiple exporters, allowing you to send data to different destinations per telemetry type. Just set the exporters entry to an object of exporter definitions and then configure the exporters per telemetry type. For example, this will send metrics and logs to an OTLP endpoint while sending traces to Datadog:

const{ Rotel, Config }=require("@streamfold/rotel");constrotel=newRotel({enabled: true,exporters: {"logs_and_metrics": Config.otlp_exporter({endpoint: "https://foo.example.com",headers: {"x-api-key": process.env.API_KEY,"x-data-set": "testing"}}),"tracing": Config.datadog_exporter({api_key: "1234abcd",}),},// Define exporters per telemetry typeexporters_traces: ["tracing"],exporters_metrics: ["logs_and_metrics"],exporters_logs: ["logs_and_metrics"]});rotel.start();

Endpoint overrides

When using the OTLP exporter over HTTP, the exporter will append /v1/traces, /v1/metrics, or /v1/logs to the endpoint URL for traces, metrics, and logs respectively. If the service you are exporting telemetry data to does not support these standard URL paths, you can individually override them for traces, metrics, and logs.

For example, to override the endpoint for traces and metrics you can do the following:

const{ Rotel, Config }=require("@streamfold/rotel");constrotel=newRotel({enabled: true,exporters: {"otlp": Config.otlp_exporter({headers: {"x-api-key": "xxxxx",},traces: {endpoint: "http://foo.example.com:4318/api/otlp/traces",},metrics: {endpoint: "http://foo.example.com:4318/api/otlp/metrics",}})},exporters_traces: ["otlp"],exporters_metrics: ["otlp"],exporters_logs: ["otlp"]});rotel.start();

Or, you can override the endpoints using environment variables:

• ROTEL_OTLP_EXPORTER_TRACES_ENDPOINT=http://foo.example.com:4318/api/otlp/traces
• ROTEL_OTLP_EXPORTER_METRICS_ENDPOINT=http://foo.example.com:4318/api/otlp/metrics
• ROTEL_OTLP_EXPORTER_METRICS_ENDPOINT=http://foo.example.com:4318/api/otlp/logs

All the OTLP exporter settings can be overridden per endpoint type (traces, metrics, logs). Any value that is not overridden will fall back to the top-level exporter configuration or the default.

Retries and timeouts

You can override the default request timeout of 5 seconds for the OTLP Exporter with the exporter setting:

• request_timeout: Takes a string time duration, so "250ms" for 250 milliseconds, "3s" for 3 seconds, etc.

Requests will be retried if they match retryable error codes like 429 (Too Many Requests) or timeout. You can control the behavior with the following exporter options:

• retry_initial_backoff: Initial backoff duration
• retry_max_backoff: Maximum backoff interval
• retry_max_elapsed_time: Maximum wall time a request will be retried for until it is marked as permanent failure

All options should be represented as string time durations.

Full OTEL example

To illustrate this further, here's a full example of how to use Rotel to send trace spans to Axiom from an application instrumented with OpenTelemetry.

The code sample depends on the following environment variables:

• ROTEL_ENABLED=true: Turn on or off based on the deployment environment
• AXIOM_DATASET: Name of an Axiom dataset
• AXIOM_API_TOKEN: Set to an API token that has access to the Axiom dataset

const{ Rotel, Config }=require("@streamfold/rotel");const{ NodeTracerProvider }=require('@opentelemetry/sdk-trace-node');const{ OTLPTraceExporter }=require('@opentelemetry/exporter-trace-otlp-grpc');const{ trace }=require('@opentelemetry/api');const{ SimpleSpanProcessor }=require('@opentelemetry/sdk-trace-base');const{ATTR_SERVICE_NAME}=require('@opentelemetry/semantic-conventions');const{ resourceFromAttributes }=require('@opentelemetry/resources');functioninitRotel(){constrotel=newRotel({enabled: true,exporters: {"axiom": Config.otlp_exporter({endpoint: "https://api.axiom.co",protocol: "http",headers: {"Authorization": "Bearer "+process.env.AXIOM_API_TOKEN,"X-Axiom-Dataset": process.env.AXIOM_DATASET}})},exporters_traces: ["axiom"],exporters_metrics: ["axiom"],exporters_logs: ["axiom"]})returnrotel;}functioninitOtel(){constexporter=newOTLPTraceExporter({url: 'http://127.0.0.1:4317',// points to out local Rotel });// Initialize the tracer provider constprovider=newNodeTracerProvider({resource: resourceFromAttributes({[ATTR_SERVICE_NAME]: 'rotel-nodejs-service',}),spanProcessors: [newSimpleSpanProcessor(exporter)],});// Register the provider as the global tracer providerprovider.register();returnprovider;}asyncfunctionsleep(ms){returnnewPromise(resolve=>setTimeout(resolve,ms));}// Main routineasyncfunctionmain(){constrotel=initRotel();constprovider=initOtel();rotel.start();console.log("Hello from example");consttracer=trace.getTracer('rotel-node-js-hello-world');console.log("starting main span");constmainSpan=tracer.startSpan('main');// sleep for a second to simulate span start/end timeawaitsleep(1000);mainSpan.end();console.log("main span ended, flushing")awaitprovider.forceFlush();awaitprovider.shutdown();rotel.stop();console.log("goodbye")}main();

For the complete example, see the hello world application.

Debugging

If you set the option debug_log to ["traces"], or the environment variable ROTEL_DEBUG_LOG=traces, then rotel will log a summary to the log file /tmp/rotel-agent.log each time it processes trace spans. You can add also specify metrics to debug metrics and logs to debug logs.

FAQ

Do I need to call rotel.stop() when I exit?

In most deployment environments you do not need to call rotel.stop() and it is generally recommended that you don't. Calling rotel.stop() will terminate the running agent on a host, so any further export calls from OTEL instrumentation will fail. In a multiprocess environment, such as clusters of node.js processes, terminating the Rotel agent from one process will terminate it for all other processes. On ephemeral deployment platforms, it is usually fine to leave the agent running until the compute instance, VM/container/isolate, terminate.

Community

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Developing

See the DEVELOPING.md doc for building and development instructions.