Anything · Lazarus or Delphi

apollo

Structured logging for Delphi — pluggable sinks, enriched context, JSON output for Seq, Loki, Datadog and more

Active · last change 5-27-2026
★ 2 on GitHub

View on GitHub

Member rating

No ratings yet.

README

Apollo

Structured logging for Delphi — fluent API, async dispatcher, pluggable sinks, OpenTelemetry.

Apollo brings structured, async logging to Delphi. Named after the god of light and truth — bringing things to light. Every project in the Olympian family emits logs through Apollo.

Quick Start

pascal

uses Apollo, Apollo.Sink.Console, Apollo.Dispatcher;

var
  LDispatcher: TApolloDispatcher;
begin
  LDispatcher := TApolloDispatcher.New;
  LDispatcher.AddSink(TApolloConsoleSink.New(llInfo));
  ApolloSetup(LDispatcher);
  LDispatcher.Start;

  ApolloInfo('server started').Field('port', 9000).Emit;
  ApolloWarn('high memory').Field('mb', 512).Emit;
  ApolloError('job failed', E).Field('job_id', '123').Emit;
end;

Fluent API

pascal

ApolloInfo('request processed')
  .Field('method', 'GET')
  .Field('path', '/users')
  .Field('status', 200)
  .Field('ms', 14)
  .TraceId('abc123')
  .SpanId('def456')
  .Emit;

Log Levels

pascal

ApolloTrace('verbose detail').Emit;
ApolloDebug('internal state').Emit;
ApolloInfo('normal event').Emit;
ApolloWarn('something unexpected').Emit;
ApolloError('something failed').Emit;
ApolloFatal('unrecoverable').Emit;

Installation

bash

git clone https://github.com/herlondf/apollo.git

Add to Delphi project search path:

pascal

apollo\src

No external dependencies — uses only System.Net.HttpClient (RTL) for HTTP sinks.

Requirements

Delphi 11 Alexandria or later
No mandatory external dependencies

Sinks

Sink	Unit	Transport
`TApolloConsoleSink`	`Apollo.Sink.Console`	Stdout with ANSI colors
`TApolloFileSink`	`Apollo.Sink.File`	NDJSON file with size rotation
`TApolloSeqSink`	`Apollo.Sink.Seq`	Seq — CLEF format over HTTP
`TApolloLokiSink`	`Apollo.Sink.Loki`	Grafana Loki push API
`TApolloElasticsearchSink`	`Apollo.Sink.Elasticsearch`	Elasticsearch Bulk API
`TApolloDatadogSink`	`Apollo.Sink.Datadog`	Datadog Logs API v2
`TApolloOTLPSink`	`Apollo.Sink.OTLP`	OpenTelemetry OTLP/HTTP `/v1/logs`

Implement IApolloSink (2 methods) to add your own.

Multiple Sinks

pascal

LDispatcher.AddSink(TApolloConsoleSink.New(llDebug));
LDispatcher.AddSink(TApolloSeqSink.New('http://seq:5341', 'my-api-key', llInfo));
LDispatcher.AddSink(TApolloLokiSink.New('http://loki:3100', llWarn));

Each sink has its own minimum level. Console shows debug; Loki only receives warnings and above.

Seq

pascal

uses Apollo.Sink.Seq;

Dispatcher.AddSink(
  TApolloSeqSink.New('http://seq:5341', 'my-api-key', llInfo)
);

Loki

pascal

uses Apollo.Sink.Loki;

LDispatcher.AddSink(
  TApolloLokiSink.New('http://loki:3100', llInfo)
    .WithLabel('app', 'my-api')
    .WithLabel('env', 'production')
);

With authentication:

pascal

LDispatcher.AddSink(
  TApolloLokiSink.New('http://loki:3100', llInfo)
    .BasicAuth('admin', 'secret')
    .WithLabel('app', 'my-api')
);

Elasticsearch

pascal

uses Apollo.Sink.Elasticsearch;

LDispatcher.AddSink(
  TApolloElasticsearchSink.New('http://es:9200', 'logs-myapp', llInfo)
    .BasicAuth('elastic', 'password')
);

Use an API key instead of user/password:

pascal

LDispatcher.AddSink(
  TApolloElasticsearchSink.New('http://es:9200', 'logs-myapp', llInfo)
    .ApiKey('my-encoded-api-key')
);

Datadog

pascal

uses Apollo.Sink.Datadog;

LDispatcher.AddSink(
  TApolloDatadogSink.New('my-dd-api-key', llInfo)
    .Service('my-api')               // optional — defaults to 'app'
    .Site('datadoghq.eu')            // optional — defaults to datadoghq.com
    .Tag('env:production,team:core') // optional — Datadog tags
);

OpenTelemetry (OTLP)

pascal

uses Apollo.Sink.OTLP;

LDispatcher.AddSink(
  TApolloOTLPSink.New('http://otel-collector:4318', llInfo)
    .ResourceAttribute('service.name', 'my-api')
    .ResourceAttribute('deployment.environment', 'production')
    .BearerToken('my-token')         // optional — most collectors require auth
);

Use a custom Authorization header when Bearer is not enough:

pascal

LDispatcher.AddSink(
  TApolloOTLPSink.New('http://otel-collector:4318', llInfo)
    .ResourceAttribute('service.name', 'my-api')
    .Authorization('Basic dXNlcjpwYXNz')
);

Context Fields

Pre-set fields that propagate to every log entry emitted by the logger:

pascal

var
  LLogger: IApolloLogger;
begin
  LLogger := TApolloLogger.New(LDispatcher)
    .WithContext('service', 'order-processor')
    .WithContext('version', 3)
    .WithContext('region', 'us-east-1');

  LLogger.Info('job started').Field('job_id', '42').Emit;
  // → message=job started  service=order-processor  version=3  region=us-east-1  job_id=42

  LLogger.Error('job failed', E).Emit;
  // → error.type + error.message + all context fields
end;

Architecture

Apollo uses a producer-consumer pattern. Application threads enqueue log entries instantly (non-blocking). A background dispatcher drains the queue in batches and fans out to sinks in parallel.

pascal

App thread ??? TThreadedQueue (capacity 10,000) ??? Background dispatcher
                                                      ???
                              TTask.Run per sink (parallel flush)
                              ConsoleSink | SeqSink | LokiSink | ...

Zero latency on the hot path — Emit is a queue push
Batch flush every 500ms or 100 entries (whichever comes first)
Stop drains remaining entries before exit

Project Structure

pascal

src/
  Apollo.pas                        Entry-point umbrella + global singleton
  Apollo.Entry.pas                  TApolloLogEntry, TApolloLogLevel
  Apollo.Sink.Interfaces.pas        IApolloSink interface
  Apollo.Dispatcher.pas             TApolloDispatcher (async queue + thread)
  Apollo.Logger.pas                 IApolloLogger, IApolloLogBuilder
  Apollo.Sink.Console.pas           Console sink (ANSI colors)
  Apollo.Sink.File.pas              File sink (NDJSON, rotation)
  Apollo.Sink.Seq.pas               Seq sink (CLEF)
  Apollo.Sink.Loki.pas              Loki sink (push API)
  Apollo.Sink.Elasticsearch.pas     Elasticsearch sink (Bulk API)
  Apollo.Sink.Datadog.pas           Datadog sink (Logs API v2)
  Apollo.Sink.OTLP.pas              OpenTelemetry OTLP sink

samples/                            Runnable examples
tests/                              DUnitX tests
docs/
  playbook/                         English guide
  playbook_pt-br/                   Guia em portugu??s

Inspiration

Apollo is inspired by Serilog (C#), Zap (Go), Winston (Node.js), and Logrus (Go). The same concepts — structured fields, async sinks, pluggable outputs — brought natively to Delphi.

The Olympian Family

Poseidon commands the seas — raw transport, the force of the waves. Triton guards his father's waters — manages what flows, holds what must not be lost. Pegasus flies through the skies — born from Medusa's blood, by the sword Hermes gave to Perseus. Hermes runs between all realms — carries messages between gods, mortals and monsters. Hefesto forges in the depths — invisible, tireless, turning raw material into finished work. Iris goes and returns — the HTTP client that calls the world. Apollo is the god of light and truth — brings everything to light.

Project	Myth	Role
Poseidon	God of the seas	Async transport layer — IOCP/epoll, raw I/O
Triton	Son of Poseidon, guardian of the depths	Generic resource pool — connections, clients, SMTP
Pegasus	Born from Poseidon's blood, ridden by heroes	HTTP framework — routing, middleware, providers
Hermes	Messenger of the gods, guide between realms	Redis client — fast key-value, pub/sub, messaging
Hefesto	Forgemaster of the gods, works unseen	Background jobs — queues, workers, retry, scheduling
Iris	Goddess of the rainbow, messenger who returns	HTTP client — fluent API, retry, pluggable transports
Apollo (this lib)	God of light and truth, brings things to light	Structured logging — async sinks, OTLP, Seq, Loki, Datadog

Contributing

See docs/CONTRIBUTING.md · docs/CONTRIBUTING_pt-br.md

License

MIT — use freely in commercial and open-source projects.

🇧🇷 Leia este documento em português: README_pt-br.md

Live chat for Free Pascal, Lazarus, Delphi and every Pascal programmer.

Aapollo

Member rating

README

Apollo

Quick Start

Fluent API

Log Levels

Installation

Requirements

Sinks

Multiple Sinks

Seq

Loki

Elasticsearch

Datadog

OpenTelemetry (OTLP)

Context Fields

Architecture

Project Structure

Inspiration

The Olympian Family

Contributing

License

apollo