Delivery Log Storage Backends

Each backend implements IEventPublishDeliveryLog. Storage packages are distributed separately and must be installed explicitly.

Note: Only one storage backend is active — subsequent Use* calls replace the previous registration.

In-Memory Storage

Package: Hermodr.Publisher.DeliveryLog.InMemory

InMemoryEventDeliveryLogRepository holds all records in a thread-safe, volatile collection. Registered as Singleton.

Characteristics

Aspect	Description
Persistence	None — records lost on process restart
Performance	Fastest — no I/O overhead
Query capability	In-memory LINQ queries
Best for	Development, testing, local debugging

Registration

builder.Services
    .AddEventPublisher()
    .AddDeliveryLog(log => log.UseInMemory());

Querying

var log = provider.GetRequiredService<InMemoryEventDeliveryLogRepository>();
var records = log.Records.Where(r => r.Outcome == EventDeliveryOutcome.Failed);

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NDJSON Rolling Files

Package: Hermodr.Publisher.DeliveryLog.NDJson

The NDJSON implementation appends each record as a JSON line to a sequentially-named file.

Characteristics

Aspect	Description
Persistence	File-based — survives process restarts
Performance	Good — sequential writes, async I/O
Query capability	Stream-based reading, filtering on read
Best for	Production, audit scenarios, external processing

File Naming

Files are named delivery-log-{yyyyMMdd-HHmmss}.ndjson in a configurable directory:

/var/logs/delivery-logs/
  delivery-log-20260614-103012.ndjson
  delivery-log-20260614-103045.ndjson
  delivery-log-20260614-104500.ndjson

Auto-Roll Behavior

The backend auto-rolls to a new file when either:

• Current file exceeds MaxFileSizeBytes (default 10 MB)
• RollInterval has elapsed

After each write, it checks the file count and deletes the oldest files beyond MaxFileCount (default 30).

Registration

builder.Services
    .AddEventPublisher()
    .AddDeliveryLog(log => log.UseNDJson(opts =>
    {
        opts.DirectoryPath = "/var/logs/delivery-logs";
        opts.MaxFileSizeBytes = 10 * 1024 * 1024;
        opts.RollInterval = TimeSpan.FromHours(6);
        opts.MaxFileCount = 30;
    }));

Options Reference

Option	Type	Default	Description
DirectoryPath	string	%TEMP%/delivery-logs	Directory for NDJSON files
MaxFileSizeBytes	long	10 MB	Size threshold for rolling
RollInterval	TimeSpan?	null	Time threshold for rolling
MaxFileCount	int	30	Max files retained (≤0 = no cleanup)

Reading NDJSON Files

var query = new DeliveryLogStreamQuery
{
    From = DateTimeOffset.UtcNow.AddHours(-1),
    Outcome = EventDeliveryOutcome.Failed
};

await foreach (var record in reader.ReadAsync(query))
{
    Console.WriteLine($"Failed: {record.Event.Type} - {record.ErrorMessage}");
}

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Entity Framework Core

Package: Hermodr.Publisher.DeliveryLog.EntityFramework

Stores records in a relational database using Kista.EntityFramework.

Characteristics

Aspect	Description
Persistence	Database — durable, transactional
Performance	Moderate — depends on database
Query capability	Full LINQ, indexes, aggregations
Best for	Production, monitoring dashboards, reporting

Registration

builder.Services
    .AddEventPublisher()
    .AddDeliveryLog(log => log.UseEntityFramework(opts =>
        opts.UseSqlServer(connectionString)));

Database Schema

The EF Core backend creates a DeliveryLogEntries table with columns for all EventDeliveryRecord fields.

Querying

using var db = provider.GetRequiredService<DeliveryLogDbContext>();

// Count failures in last hour
var failureCount = await db.DeliveryLogEntries
    .CountAsync(e => e.Outcome == EventDeliveryOutcome.Failed 
                  && e.Timestamp > DateTimeOffset.UtcNow.AddHours(-1));

// Average latency by event type
var avgLatency = await db.DeliveryLogEntries
    .Where(e => e.EventTime > DateTimeOffset.UtcNow.AddHours(-1))
    .GroupBy(e => e.Event.Type)
    .Select(g => new 
    {
        EventType = g.Key,
        AvgLatencyMs = g.Average(e => e.ElapsedTime.TotalMilliseconds)
    })
    .ToListAsync();

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Backend Comparison

Backend	Persistence	Performance	Query Capability	Best For
In-Memory	None	Fastest	LINQ	Development/Testing
NDJSON	Files	Good	Stream-based	Production, audit
EF Core	Database	Moderate	Full LINQ	Production, reporting

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Related Pages

• Delivery Log Overview
• NDJSON Backend
• EF Core Backend