====== Runbook: Check Logs ======

<WRAP round info>
**Duration:** ~10 minutes \\
**Role:** Gateway Operator \\
**Frequency:** Daily / On issues
</WRAP>

Analysis of Gateway logs for error diagnosis and monitoring.

----

===== Workflow =====

<mermaid>
flowchart TD
    A[Open logs] --> B[Filter for ERROR]
    B --> C{Errors found?}
    C -->|Yes| D[Analyze error]
    C -->|No| E[Filter for WARN]
    D --> F[Take action]
    E --> G{Warnings?}
    G -->|Yes| H[Document]
    G -->|No| I[OK - Done]
    F --> I
    H --> I

    style I fill:#e8f5e9
    style D fill:#ffebee
    style H fill:#fff3e0
</mermaid>

----

===== 1. Log Locations =====

| Platform | Path |
|----------|------|
| Windows (Console) | Console output |
| Windows (Service) | ''%GATEWAY_ROOT%\logs\'' or Event Log |
| Linux (systemd) | ''journalctl -u data-gateway'' |
| Docker | ''docker logs gateway'' |

----

===== 2. Show Recent Logs =====

**Windows (File):**

<code powershell>
# Last 50 lines
Get-Content -Path "%GATEWAY_ROOT%\logs\gateway.log" -Tail 50

# Live tail
Get-Content -Path "%GATEWAY_ROOT%\logs\gateway.log" -Wait -Tail 10
</code>

**Linux (systemd):**

<code bash>
# Last 100 lines
journalctl -u data-gateway -n 100 --no-pager

# Live tail
journalctl -u data-gateway -f
</code>

**Docker:**

<code bash>
# Last 100 lines
docker logs --tail 100 gateway

# Live tail
docker logs -f gateway
</code>

----

===== 3. Filter for Errors =====

**Windows:**

<code powershell>
# ERROR entries
Select-String -Path "%GATEWAY_ROOT%\logs\*.log" -Pattern "ERROR|Exception"

# Today
Get-Content "%GATEWAY_ROOT%\logs\gateway.log" | Where-Object { $_ -match "ERROR" -and $_ -match (Get-Date -Format "yyyy-MM-dd") }
</code>

**Linux:**

<code bash>
# ERROR entries
journalctl -u data-gateway --since today | grep -E "ERROR|Exception"

# Or in file
grep -E "ERROR|Exception" /var/log/gateway/gateway.log
</code>

----

===== 4. Common Log Patterns =====

**Successful request:**
<code>
[INFO] GET /api/v1/dsn/demo/tables 200 45ms
</code>

**Error:**
<code>
[ERROR] GET /api/v1/dsn/invalid/tables 404 Database 'invalid' not found
[ERROR] POST /api/v1/dsn/demo/query 500 SqlException: Invalid syntax
</code>

**Warning:**
<code>
[WARN] Slow query detected: 2340ms for GET /api/v1/dsn/production/tables/BigTable
</code>

----

===== 5. Adjust Log Level =====

In ''appsettings.json'':

<code javascript>
{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "WvdS.WebAPI.Data.Gateway": "Debug"
    }
  }
}
</code>

| Level | Usage |
|-------|-------|
| ''Trace'' | Very detailed (development) |
| ''Debug'' | Debugging information |
| ''Information'' | Normal operations (default) |
| ''Warning'' | Potential problems |
| ''Error'' | Errors that were handled |
| ''Critical'' | Severe errors, crash |

----

===== 6. Checklist =====

| # | Check | Done |
|---|-------|------|
| 1 | ERROR entries reviewed | [ ] |
| 2 | WARN entries reviewed | [ ] |
| 3 | Slow queries noted | [ ] |
| 4 | Errors documented/reported | [ ] |
| 5 | Log rotation active | [ ] |

----

===== Troubleshooting =====

| Log Message | Cause | Solution |
|-------------|-------|----------|
| ''Database not found'' | DSN not configured | Check appsettings.json |
| ''Connection refused'' | DB not reachable | Check firewall/network |
| ''SqlException: Login failed'' | Wrong credentials | Check password |
| ''OutOfMemoryException'' | Query too large | Set ''$top'' limit |
| ''Timeout expired'' | DB too slow | Optimize index |

----

===== Set Up Log Rotation =====

**Serilog (appsettings.json):**

<code javascript>
{
  "Serilog": {
    "WriteTo": [
      {
        "Name": "File",
        "Args": {
          "path": "logs/gateway-.log",
          "rollingInterval": "Day",
          "retainedFileCountLimit": 30
        }
      }
    ]
  }
}
</code>

----

===== Related Runbooks =====

  * [[.:health-check|Health Check]] - Availability check
  * [[.:server-starten|Start Server]] - On crash
  * [[..:monitoring:alerting|Alerting]] - Automatic notification

----

<< [[.:health-check|<- Health Check]] | [[..:start|-> Operator Overview]] >>

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//Wolfgang van der Stille @ EMSR DATA d.o.o. - Data Gateway Professional//

{{tag>operator runbook logs troubleshooting}}