kroki: A Java repository from MarcelWaldvogel

Kroki provides a unified API with support for BlockDiag (BlockDiag, SeqDiag, ActDiag, NwDiag, PacketDiag, RackDiag), BPMN, Bytefield, C4 (with PlantUML), Ditaa, Erd, Excalidraw, GraphViz, Mermaid, Nomnoml, Pikchr, PlantUML, SvgBob, UMLet, Vega, Vega-Lite and WaveDrom… and more to come!

Quickstart

This section offers a basic tutorial for evaluating Kroki. More comprehensive installation instructions are in the Kroki documentation.

Usage

Kroki uses a simple algorithm (deflate + base64) to encode your diagram in the URL:

GET /plantuml/svg/SyfFKj2rKt3CoKnELR1Io4ZDoSa70000

You can also call Kroki with POST:

POST /

{
  "diagram_source": "Bob -> Alice : hello",
  "diagram_type": "plantuml",
  "output_format": "svg"
}

In this case, you don’t need to encode your diagram.

It’s also possible to send your diagram as plain text using the Content-Type header. The output format will be specified using the Accept header and the diagram source will be sent as the request body:

POST /plantuml

Accept: image/svg+xml
Content-Type: text/plain

Bob -> Alice : hello

You can also define the output format in the URL if you don’t want to add an Accept header:

POST /plantuml/svg

Content-Type: text/plain

Bob -> Alice : hello

The same concept applies when sending the diagram as JSON:

POST /plantuml/svg

{
  "diagram_source": "Bob -> Alice : hello"
}

Project layout

Kroki has a modular architecture:

server: A Java web server (powered by Vert.x) that acts as a gateway. Kroki server is built using Maven.
umlet: A tiny Java API on top of UMlet (mini) to generate diagrams.
nomnoml: A Node.js CLI on top of the Nomnoml diagram library.
vega: A Node.js CLI on top of the vega diagram library. Also supports Vega-Lite concise grammar.
blockdiag: A companion web server written in Python (powered by Flask and Gunicorn) that provides BlockDiag, SeqDiag, ActDiag, NwDiag, PacketDiag and RackDiag diagrams libraries.
mermaid: A companion web server written in JavaScript (powered by micro) that provides Mermaid diagram library.
bpmn: A companion web server written in JavaScript (powered by micro) that provides bpmn-js diagram library.
bytefield: A Node.js CLI on top of the bytefield-svg diagram library.
wavedrom: A Node.js CLI on top of the wavedrom diagram library.
excalidraw: A companion web server written in JavaScript (powered by micro) that provides Excalidraw.

Build

Gateway Server

The first step is to install the local dependencies in your local repository using make:

$ make installLocalDependencies

Then you can build the project using Maven:

$ make buildServer

Docker Images

To build all the Docker images, use the following command:

$ sudo make buildDockerImages

Note	`sudo` might not be needed depending on your distribution and `docker` configuration.

Run

Once the Docker images are built, you can run Kroki using docker:

$ docker run -d -p 8000:8000 yuzutech/kroki

Companion Containers

If you want to use BlockDiag, ActDiag, NwDiag, SeqDiag, PacketDiag, RackDiag or Mermaid, then you will also need to start companion containers.

You can use docker-compose to run multiple containers:

docker-compose.yml

version: "3"
services:
  core:
    image: yuzutech/kroki
    environment:
      - KROKI_BLOCKDIAG_HOST=blockdiag
      - KROKI_MERMAID_HOST=mermaid
      - KROKI_BPMN_HOST=bpmn
      - KROKI_EXCALIDRAW_HOST=excalidraw
    ports:
      - "8000:8000"
  blockdiag:
    image: yuzutech/kroki-blockdiag
    ports:
      - "8001:8001"
  mermaid:
    image: yuzutech/kroki-mermaid
    ports:
      - "8002:8002"
  bpmn:
    image: yuzutech/kroki-bpmn
    ports:
      - "8003:8003"
  excalidraw:
    image: yuzutech/kroki-excalidraw
    ports:
      - "8004:8004"

$ docker-compose up -d

MarcelWaldvogel/kroki