Glossary

A

Autostart

A boolean flag in startup.yml that controls whether a generator instance starts automatically when the Eventum application launches. Instances with autostart: false are registered but remain inactive until started manually through the REST API or Studio.

B

Backpressure

A flow-control mechanism that prevents memory overflow when one pipeline stage is slower than the one feeding it. If the event queue is full, event production pauses. If the timestamp queue is full, input generation pauses. Queue depths are controlled by queue.max_timestamp_batches and queue.max_event_batches.

Batch

A group of events processed together as a unit. Batching amortizes per-event overhead and is controlled by two parameters: batch.size (maximum events per batch) and batch.delay (maximum seconds before flushing a partial batch). See eventum.yml — Generation.

C

Chain

A picking mode that cycles through templates in a fixed, user-defined sequence. Unlike spin (which uses the natural order), chain lets you specify an explicit order with optional repeats.

Chance

A picking mode that selects a template using weighted probabilities. Each template has a chance value (0.0–1.0); the chances across all templates must sum to 1.0.

Cryptfile

An AES-encrypted file that stores secrets, managed by the keyrings.cryptfile library. Protected by a keyring password provided at runtime. See Secrets.

E

Event plugin

The second stage of the generator pipeline. Receives timestamps from input plugins and produces event strings. See event plugins for available types.

Eventum Studio

The built-in web interface shipped with Eventum. Provides a visual dashboard, generator management, plugin editors, event debugger, and administration tools — all accessible from a browser. See Eventum Studio.

eventum.yml

The main application configuration file. Defines server settings (host, port, SSL, authentication), generation defaults (timezone, batching, concurrency), logging, and file paths. See eventum.yml reference.

F

Fan-out

The delivery model used by output plugins. Every event produced by the event plugin is sent to all configured output plugins. There is no routing or filtering — each output receives a copy of every event.

Finite State Machine (FSM)

A picking mode for stateful event sequences. Each template is a state with defined transitions. Transitions can be unconditional or conditional (evaluated at runtime using Jinja2 expressions). Useful for modeling workflows like user sessions.

Formatter

A transformation layer on output plugins that reshapes event strings before delivery. See Formatters for available formats.

G

Generator

The core execution unit in Eventum. A generator is a self-contained pipeline that produces events through three stages: input (when), event (what), and output (where). Each generator runs independently with its own configuration, state, and metrics. See Generator concepts.

generator.yml

The configuration file for a single generator. Defines the input plugin(s), event plugin, and output plugin(s) that form the generator pipeline. Located inside a generator directory. See generator.yml reference.

Globals

A state scope shared across all generators in the application. Accessible as globals in templates. Thread-safe — reads and writes are synchronized. Useful for cross-generator coordination. See Producing events — State.

H

Hot reload

Reloading configuration without stopping the application. Triggered by sending SIGHUP to the Eventum process or clicking Restart in Studio. All generators stop, configuration is re-read, and generators restart with updated settings.

I

Input plugin

The first stage of the generator pipeline. Produces timestamps that define when events should be generated. See input plugins for available types.

Instance

A running (or finished) copy of a generator. Each instance has a unique ID, its own metrics, logs, and lifecycle. Multiple instances can use the same generator project with different parameters. Managed through the Instances page in Studio or the REST API.

K

Keep order

A generation flag (keep_order: true) that serializes output writes to maintain strict chronological order. When disabled (default), output plugins write concurrently for higher throughput.

Keyring

The encrypted credential store used by Eventum. Secrets are added with eventum-keyring set and referenced in configs via ${secrets.name} tokens. See Secrets.

L

Live mode

The default operating mode (live_mode: true). Timestamps are released at their real wall-clock times — the generator waits until each scheduled moment arrives before emitting the event. Contrast with sample mode.

Locals

A state scope private to a single template. Each template has its own locals dictionary, invisible to other templates. Useful for per-template counters and accumulators. See Producing events — State.

M

Merging

The process of combining timestamps from multiple input plugins in a single generator. Timestamps are interleaved in chronological order so the event plugin receives a single unified stream. See Scheduling — Merging.

Module

A context variable available in templates that acts as a gateway to Python packages. Provides access to Faker (module.faker), Mimesis (module.mimesis), the built-in rand helper (module.rand), and any installed Python package (module.json, module.math, etc.).

Multiplier

A component in time-patterns scheduling that sets the baseline number of events per period. Combined with a randomizer to add variance. See Scheduling — Multiplier.

O

Oscillator

A component in time-patterns scheduling that divides time into repeating periods (e.g., every hour, every day). Defined by a start time, end time, period length, and period unit. See Scheduling — Oscillator.

Output plugin

The third stage of the generator pipeline. Receives formatted events and writes them to a destination. See output plugins for available types.

P

Parameters

Runtime values injected into configuration files through ${params.name} tokens. Defined in startup.yml per-generator or passed via the --params CLI flag. See Parameters.

Picking mode

A strategy that determines which template(s) render on each event timestamp. See Producing events — Picking modes for available modes.

Pipeline

The three-stage data flow inside a generator: Input (timestamps) → Event (strings) → Output (delivery). Each stage is handled by one or more plugins. See Generator — The three-stage pipeline.

Plugin

A swappable, self-contained component that handles one stage of the generator pipeline. Plugins are identified by type (input, event, output) and name (e.g., cron, template, clickhouse). See Plugins concepts.

Project

In Studio, a project corresponds to a generator directory on disk — a generator.yml file and its supporting resources (templates, scripts, samples). The Projects page provides visual editors for each project.

Q

Queue

An internal buffer between pipeline stages. Two queues exist per generator: a timestamp queue (input → event) and an event queue (event → output). Queue sizes control backpressure.

R

Rand

A lightweight built-in helper available in templates as module.rand. Provides random choices, weighted selection, numbers (integer, float, gaussian), and string generation (hex, digits, letters). See Producing events — rand.

Randomizer

A component in time-patterns scheduling that adds natural variance to the baseline event count set by the multiplier. Controlled by a deviation parameter. See Scheduling — Randomizer.

Replay plugin

An event plugin that reads events from existing log or data files instead of generating new ones. Optionally replaces embedded timestamps with current values using regex patterns.

REST API

HTTP endpoints for programmatic control of Eventum — managing generators, querying metrics, reading logs, and modifying configuration. Enabled via api_enabled: true in eventum.yml. See API reference.

S

Sample mode

An operating mode (live_mode: false) where all timestamps are released as fast as possible, ignoring the wall clock. Used for quickly generating large datasets, benchmarking, or backfilling. Contrast with live mode.

Samples

External datasets loaded into template context from CSV, JSON, or inline item lists. Defined in generator.yml and accessed in templates via the samples variable. See Template plugin — Samples.

Script plugin

An event plugin that executes a Python function to produce events. The function receives the timestamp, tags, and parameters, and returns one or more event strings. Used when Jinja2 templates cannot express the required logic.

Secrets

Encrypted credentials stored in the keyring and referenced in configs via ${secrets.name} tokens. Managed with the eventum-keyring CLI or the Secrets page in Studio. See Secrets.

Shared

A state scope visible to all templates within the same generator. Accessible as shared in templates. Useful for cross-template coordination like maintaining a shared counter or session pool. See Producing events — State.

Skip past

A boolean flag (skip_past) that controls whether timestamps in the past are discarded when a generator starts. When true (default), only future timestamps are emitted. When false, past timestamps are released immediately as a burst.

Spin

A picking mode that cycles through templates in round-robin order — template 1, template 2, ..., template N, template 1, and so on.

Spreader

A component in time-patterns scheduling that distributes events within each period using a probability distribution (uniform, triangular, beta). Controls the intra-period traffic shape. See Scheduling — Spreader.

startup.yml

The configuration file that lists which generators to run, with per-generator overrides for mode, parameters, and generation settings. See startup.yml reference.

T

Tags

Arbitrary string labels attached by input plugins to timestamps. Tags are propagated through the pipeline and available in templates via the tags variable. Useful for varying event content based on the scheduling source.

Template plugin

The primary event plugin that renders Jinja2 templates with access to data-generation libraries, parameters, samples, and persistent state. Supports multiple templates with configurable picking modes.

Timestamp

A timezone-aware datetime value produced by an input plugin. Represents the scheduled moment for an event. Passed to the event plugin as the timestamp context variable.

V

Variable substitution

A pre-processing step that replaces ${params.name} and ${secrets.name} tokens in YAML configuration files before parsing. Uses Jinja2 syntax internally. See Parameters and Secrets.

VersatileDatetime

A flexible datetime format accepted by input plugins. Supports ISO 8601 (2025-01-01T00:00:00Z), human-readable strings (January 1, 2025), keywords (now, never), and relative expressions (+1h, -30m). See generator.yml — VersatileDatetime.