OpenTelemetry metrics integration for Soklet, implemented via MetricsCollector.

This Soklet add-on library provides OpenTelemetryMetricsCollector, a production-oriented implementation of Soklet's MetricsCollector interface.

It records HTTP + SSE lifecycle telemetry into OpenTelemetry Meter instruments (counters, up-down counters, and histograms), so your existing OTel pipeline/exporter stack can collect and ship metrics.

Its only dependency other than Soklet is opentelemetry-java (the Java implementation of the OpenTelemetry API).

Like Soklet, Java 17+ is required.

<dependency>
  <groupId>com.soklet</groupId>
  <artifactId>soklet-otel</artifactId>
  <version>1.1.0</version>
</dependency>

Create a collector and wire it into SokletConfig:

import com.soklet.SokletConfig;
import com.soklet.Server;
import com.soklet.otel.OpenTelemetryMetricsCollector;
import io.opentelemetry.api.OpenTelemetry;

// Acquire an OpenTelemetry instance from wherever you'd like...
OpenTelemetry openTelemetry = myOpenTelemetry();

// ...and use it to drive Soklet's OpenTelemetryMetricsCollector.
SokletConfig config = SokletConfig.withServer(
  Server.fromPort(8080)
).metricsCollector(
  OpenTelemetryMetricsCollector.withOpenTelemetry(openTelemetry)
    // Optional: SOKLET for fully-custom soklet.* HTTP metric names
    // .metricNamingStrategy(OpenTelemetryMetricsCollector.MetricNamingStrategy.SOKLET)
    .instrumentationName("com.mycompany.myapp.soklet")
    .instrumentationVersion("1.0.0")
    .build()
).build();

Related API references:

• OpenTelemetryMetricsCollector
• OpenTelemetryMetricsCollector.MetricNamingStrategy
• OpenTelemetry
• Meter
• SokletConfig
• Server
• MetricsCollector

If you already have a Meter, wire directly:

OpenTelemetryMetricsCollector collector = 
  OpenTelemetryMetricsCollector.withMeter(myMeter).build();

HTTP metrics (default strategy: SEMCONV):

• http.server.active_requests
• http.server.request.duration
• http.server.request.body.size
• http.server.response.body.size

Soklet-specific metrics (all strategies):

• soklet.server.connections.accepted
• soklet.server.connections.rejected
• soklet.server.requests.accepted
• soklet.server.requests.rejected
• soklet.server.request.read.failures
• soklet.server.response.write.duration
• soklet.server.response.write.failures
• soklet.sse.connections.active
• soklet.sse.connections.established
• soklet.sse.connections.handshake.failures
• soklet.sse.connections.terminated
• soklet.sse.connection.duration
• soklet.sse.events.written
• soklet.sse.events.write.failures
• soklet.sse.events.write.duration
• soklet.sse.events.delivery.lag
• soklet.sse.events.payload.size
• soklet.sse.events.queue.depth
• soklet.sse.events.dropped
• soklet.sse.comments.written
• soklet.sse.comments.write.failures
• soklet.sse.comments.write.duration
• soklet.sse.comments.delivery.lag
• soklet.sse.comments.payload.size
• soklet.sse.comments.queue.depth
• soklet.sse.comments.dropped
• soklet.sse.broadcast.attempted
• soklet.sse.broadcast.enqueued
• soklet.sse.broadcast.dropped

Common attributes:

• soklet.server.type (standard_http, server_sent_event)
• soklet.failure.reason
• error.type
• http.request.method
• url.scheme
• http.route
• http.response.status_code
• soklet.sse.termination.reason
• soklet.sse.drop.reason
• soklet.sse.comment.type
• soklet.sse.broadcast.payload.type

• http.route uses Soklet route declarations when available (for example /widgets/{id}).
• With SEMCONV, unmatched requests omit http.route (per OTel guidance).
• With SOKLET, unmatched requests are grouped under _unmatched.
• Request paths, remote addresses, and raw query values are intentionally not emitted as attributes by default.

• The collector is thread-safe and designed for callback hot paths (no I/O or blocking operations in callback methods).
• MetricNamingStrategy.SEMCONV is the default for HTTP metric names.
• snapshot() / snapshotText() from MetricsCollector are not implemented here; use your OpenTelemetry backend/exporter to query metrics.

For Soklet documentation and lifecycle semantics, see https://www.soklet.com.