Connect to Seq

This page describes how consuming apps connect to a Seq resource that’s already modeled in your AppHost. For the AppHost API surface — adding a Seq resource, data volumes, EULA acceptance, and endpoints — see Seq hosting integration.

When you reference a Seq resource from your AppHost, Aspire injects the connection information into the consuming app as environment variables. Your app can either read those environment variables directly — the pattern works the same from any language — or, in C#, use the Aspire.Seq client integration for automatic OpenTelemetry log and trace export.

Connection properties

Aspire exposes each property as an environment variable named [RESOURCE]_[PROPERTY]. For instance, the Uri property of a resource called seq becomes SEQ_URI.

The Seq resource exposes the following connection properties:

Property Name	Description
Host	The hostname or IP address of the Seq server
Port	The port number the Seq server is listening on
Uri	The connection URI, with the format http://{Host}:{Port}

Example connection string:

Uri: http://localhost:5341

Connect from your app

Pick the language your consuming app is written in. Each example assumes your AppHost adds a Seq resource named seq and references it from the consuming app.

C#

For C# apps, the recommended approach is the Aspire.Seq client integration. It registers OpenTelemetry Protocol (OTLP) exporters through dependency injection so that logs and traces are automatically forwarded to Seq. If you’d rather read environment variables directly, see the Read environment variables section at the end of this tab.

Install the client integration

Install the 📦 Aspire.Seq NuGet package in the client-consuming project:

.NET CLI

.NET CLI — Add Aspire.Seq package

dotnet add package Aspire.Seq

Program.cs (C# file-based app)

Program.cs

#:package Aspire.Seq@*

PackageReference (*.csproj)

XML — Add Aspire.Seq package reference

<PackageReference Include="Aspire.Seq" Version="*" />

Register the Seq endpoint

In Program.cs, call AddSeqEndpoint on your IHostApplicationBuilder to register OTLP exporters that send logs and traces to Seq:

C# — Program.cs

builder.AddSeqEndpoint(connectionName: "seq");

İpucu

The connectionName must match the Seq resource name from the AppHost. For more information, see Add Seq resource.

Configuration

The Aspire.Seq client integration offers multiple ways to provide configuration.

Configuration providers. The client integration supports Microsoft.Extensions.Configuration. It loads SeqSettings from appsettings.json (or any other configuration source) by using the Aspire:Seq key:

JSON — appsettings.json

{
  "Aspire": {
    "Seq": {
      "DisableHealthChecks": false,
      "ServerUrl": "http://localhost:5341"
    }
  }
}

Named configuration. When connecting to multiple Seq instances, use named keys under Aspire:Seq:

JSON — appsettings.json

{
  "Aspire": {
    "Seq": {
      "seq1": {
        "ServerUrl": "http://seq1:5341",
        "DisableHealthChecks": true
      },
      "seq2": {
        "ServerUrl": "http://seq2:5341",
        "DisableHealthChecks": false
      }
    }
  }
}

Then register each instance by its connection name:

C# — Program.cs

builder.AddSeqEndpoint("seq1");
builder.AddSeqEndpoint("seq2");

Inline delegates. Pass an Action<SeqSettings> to configure settings inline:

C# — Program.cs

builder.AddSeqEndpoint("seq", static settings =>
{
    settings.DisableHealthChecks = true;
    settings.ServerUrl = "http://localhost:5341";
});

Client integration health checks

By default, Aspire client integrations enable health checks. The Aspire.Seq integration adds a health check that attempts to connect to the Seq server’s /health endpoint when DisableHealthChecks is false. The health check is wired into the /health HTTP endpoint, where all registered health checks must pass before the app is considered ready to accept traffic.

Observability and telemetry

Because Seq is a telemetry sink, the Aspire.Seq integration does not emit tracing activities or metrics of its own. It configures the following log category:

Logging categories:

• Seq

Read environment variables in C#

If you prefer not to use the Aspire client integration, you can read the Aspire-injected URI directly from the environment and configure the OpenTelemetry OTLP exporter manually:

C# — Program.cs

using OpenTelemetry.Logs;
using OpenTelemetry.Trace;

var seqUri = Environment.GetEnvironmentVariable("SEQ_URI");

builder.Logging.AddOpenTelemetry(logging =>
{
    logging.AddOtlpExporter(otlp => otlp.Endpoint = new Uri($"{seqUri}/ingest/otlp/v1/logs"));
});

builder.Services.AddOpenTelemetry()
    .WithTracing(tracing =>
    {
        tracing.AddOtlpExporter(otlp => otlp.Endpoint = new Uri($"{seqUri}/ingest/otlp/v1/traces"));
    });

Go

Use the OpenTelemetry Go SDK with an OTLP HTTP exporter to send logs and traces to Seq:

Terminal

go get go.opentelemetry.io/otel
go get go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp
go get go.opentelemetry.io/otel/sdk/trace

Read the injected environment variable and configure the exporter:

Go — main.go

package main

import (
    "context"
    "fmt"
    "os"

    "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
    "go.opentelemetry.io/otel/sdk/trace"
)

func main() {
    // Read the Aspire-injected Seq URI
    seqUri := os.Getenv("SEQ_URI")

    exporter, err := otlptracehttp.New(context.Background(),
        otlptracehttp.WithEndpointURL(fmt.Sprintf("%s/ingest/otlp/v1/traces", seqUri)),
        otlptracehttp.WithInsecure(),
    )
    if err != nil {
        panic(err)
    }

    tp := trace.NewTracerProvider(trace.WithBatcher(exporter))
    defer tp.Shutdown(context.Background())

    // Use tp as your global TracerProvider...
}

Not

Seq accepts OTLP over HTTP. Use the /ingest/otlp/v1/traces and /ingest/otlp/v1/logs paths on the Seq URI.

Python

Use the OpenTelemetry Python SDK with an OTLP exporter to send telemetry to Seq:

Terminal

pip install opentelemetry-sdk opentelemetry-exporter-otlp-proto-http

Read the injected environment variable and configure the exporter:

Python — app.py

import os
from opentelemetry import trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import BatchSpanProcessor
from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter

# Read the Aspire-injected Seq URI
seq_uri = os.getenv("SEQ_URI")

exporter = OTLPSpanExporter(
    endpoint=f"{seq_uri}/ingest/otlp/v1/traces",
)

provider = TracerProvider()
provider.add_span_processor(BatchSpanProcessor(exporter))
trace.set_tracer_provider(provider)

# Use trace.get_tracer(__name__) to create spans...

Alternatively, install seqlog to send structured log events directly to Seq via its native JSON ingestion endpoint:

Terminal

pip install seqlog

Python — app.py

import os
import logging
import seqlog

seq_uri = os.getenv("SEQ_URI")

seqlog.log_to_seq(
    server_url=seq_uri,
    level=logging.INFO,
    batch_size=10,
    auto_flush_timeout=2,
)

logging.info("Hello from Python via Seq!")

TypeScript

Use the OpenTelemetry JS SDK with an OTLP HTTP exporter to send telemetry to Seq:

Terminal

npm install @opentelemetry/sdk-node @opentelemetry/exporter-trace-otlp-http @opentelemetry/exporter-logs-otlp-http

Read the injected environment variable and configure the exporters:

TypeScript — tracing.ts

import { NodeSDK } from '@opentelemetry/sdk-node';
import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-http';
import { OTLPLogExporter } from '@opentelemetry/exporter-logs-otlp-http';

// Read the Aspire-injected Seq URI
const seqUri = process.env.SEQ_URI!;

const sdk = new NodeSDK({
    traceExporter: new OTLPTraceExporter({
        url: `${seqUri}/ingest/otlp/v1/traces`,
    }),
    logRecordProcessor: new (await import('@opentelemetry/sdk-logs')).BatchLogRecordProcessor(
        new OTLPLogExporter({ url: `${seqUri}/ingest/otlp/v1/logs` })
    ),
});

sdk.start();

Alternatively, use the seq-logging package to send structured log events to Seq via its native HTTP API:

Terminal

npm install seq-logging

TypeScript — index.ts

import * as seq from 'seq-logging';

// Read the Aspire-injected Seq URI
const seqUri = process.env.SEQ_URI!;

const logger = new seq.Logger({ serverUrl: seqUri });

logger.emit({
    timestamp: new Date(),
    level: 'Information',
    messageTemplate: 'Hello from {Language}!',
    properties: { Language: 'TypeScript' },
});

await logger.close();

İpucu

If your app expects specific environment variable names different from the Aspire defaults, you can pass individual connection properties from the AppHost using WithEnvironment (C#) or withEnvironment (TypeScript). See Pass custom environment variables in the hosting integration reference.