CSharpEssentials.LoggerHelper.Sink.Elasticsearch 5.2.2

CSharpEssentials.LoggerHelper.Sink.Elasticsearch

Elasticsearch / OpenSearch indexing with automatic index template registration for CSharpEssentials.LoggerHelper.

Targets: net8.0 · net9.0 · net10.0 — Part of the CSharpEssentials.LoggerHelper ecosystem. Install only the sinks you need.

Install

dotnet add package CSharpEssentials.LoggerHelper
dotnet add package CSharpEssentials.LoggerHelper.Sink.Elasticsearch

Quick Setup — JSON

Add to appsettings.json:

{
 "LoggerHelper": {
 "ApplicationName": "MyApp",
 "Routes": [
 { "Sink": "Elasticsearch", "Levels": ["Information", "Warning", "Error", "Fatal"] }
 ],
 "Sinks": {
 "Elasticsearch": {
 "NodeUris": "http://localhost:9200",
 "IndexFormat": "myapp-logs-{0:yyyy.MM.dd}"
 }
 }
 }
}

// Program.cs
builder.Services.AddLoggerHelper(builder.Configuration);
var app = builder.Build();
app.UseLoggerHelper(); // ← required: activates sinks and registers middleware

Index template registration is automatic. The sink calls Elasticsearch on startup to register the index template — no manual Kibana/DevTools setup needed.

Quick Setup — Fluent API

builder.Services.AddLoggerHelper(b => b
 .WithApplicationName("MyApp")
 .AddRoute("Elasticsearch", LogEventLevel.Information, LogEventLevel.Warning, LogEventLevel.Error, LogEventLevel.Fatal)
 .ConfigureElasticsearch(e => {
 e.NodeUris = "http://localhost:9200";
 e.IndexFormat = "myapp-logs-{0:yyyy.MM.dd}";
 })
);
var app = builder.Build();
app.UseLoggerHelper(); // ← required

What You'll See

Each log event is indexed as a JSON document:

{
 "@timestamp": "2026-06-01T14:23:01.123Z",
 "level": "Information",
 "message": "Order 42 placed by usr_99",
 "messageTemplate": "Order {OrderId} placed by {UserId}",
 "fields": {
 "OrderId": 42,
 "UserId": "usr_99",
 "ApplicationName": "MyApp"
 }
}

Documents land in the index matching your IndexFormat (e.g. myapp-logs-2026年06月01日). Query them in Kibana, OpenSearch Dashboards, or with the Elasticsearch REST API.

Index Format

The IndexFormat string uses standard .NET date format tokens applied to the current UTC date:

OpenSearch Compatibility

This sink is fully compatible with OpenSearch — use the same configuration, pointing NodeUris at your OpenSearch node:

"NodeUris": "http://localhost:9200"

OpenSearch exposes the same REST API as Elasticsearch 7.x on port 9200 by default.

Configuration Options

autoRegisterTemplate is always true — the sink registers the index template automatically on startup. This is not user-configurable but can be safely repeated (idempotent).

Troubleshooting

Quick Local Setup with Docker

# Elasticsearch
docker run -d --name elasticsearch \
 -e "discovery.type=single-node" \
 -e "xpack.security.enabled=false" \
 -p 9200:9200 \
 docker.elastic.co/elasticsearch/elasticsearch:8.13.0
# Kibana (optional — for log visualization)
docker run -d --name kibana \
 --link elasticsearch:elasticsearch \
 -p 5601:5601 \
 docker.elastic.co/kibana/kibana:8.13.0

Then set NodeUris to "http://localhost:9200" and open Kibana at http://localhost:5601.

WSL users: if the connection times out, use http://127.0.0.1:9200 instead of http://localhost:9200. WSL can route localhost to an IPv6 address that Docker does not expose, causing silent failures.

Viewing Logs in Kibana — Step by Step

Once your app is running and sending logs, follow these steps to visualize them.

Step 1 — Verify the index exists

1. Open Kibana at http://localhost:5601
2. Open the left menu (☰) → Stack Management (gear icon at the bottom)
3. Under Data → click Index Management
4. Look for your index (e.g. myapp-logs-2026年07月03日) — the Docs count column must be greater than zero

If the index is missing, the sink is not writing. Check NodeUris and confirm app.UseLoggerHelper() is called.

Step 2 — Create a Data View

A Data View is how Kibana maps an index pattern to its query engine.

1. Still in Stack Management → under Kibana → click Data Views
2. Click Create data view
3. In the Index pattern field enter: myapp-logs-* (the * wildcard covers all daily indices)
4. Kibana confirms the matched indices in real time
5. In the Timestamp field dropdown select @timestamp
6. Click Save data view

Step 3 — Browse logs in Discover

1. Open the left menu (☰) → Analytics → Discover
2. Select your data view from the dropdown in the top-left (e.g. myapp-logs-*)
3. Set the time filter in the top-right to Last 15 minutes (or the period when your app ran)
4. Log events appear in the table — click any row to expand the full JSON document

Each document exposes all structured properties set via BeginScope or call-site parameters (e.g. fields.ApplicationName, fields.RenderedMessage, fields.MachineName) and is fully searchable with KQL: fields.ApplicationName : "MyApp" and level : "Error".

Links

• Documentation
• Elasticsearch
• CSharpEssentials.LoggerHelper (core)
• GitHub Repository
• MIT License