diagrams/docs/guides/edge.md

---
id: edge
title: Edges
---

Edge is representing an edge between Nodes.

## Basic

Edge is an object representing a connection between Nodes with some additional properties.

An edge object contains three attributes: **label**, **color** and **style** which mirror corresponding graphviz edge attributes.

```python
from diagrams import Cluster, Diagram, Edge
from diagrams.onprem.analytics import Spark
from diagrams.onprem.compute import Server
from diagrams.onprem.database import PostgreSQL
from diagrams.onprem.inmemory import Redis
from diagrams.onprem.aggregator import Fluentd
from diagrams.onprem.monitoring import Grafana, Prometheus
from diagrams.onprem.network import Nginx
from diagrams.onprem.queue import Kafka

with Diagram(name="Advanced Web Service with On-Premise (colored)", show=False):
    ingress = Nginx("ingress")

    metrics = Prometheus("metric")
    metrics << Edge(color="firebrick", style="dashed") << Grafana("monitoring")

    with Cluster("Service Cluster"):
        grpcsvc = [
            Server("grpc1"),
            Server("grpc2"),
            Server("grpc3")]

    with Cluster("Sessions HA"):
        master = Redis("session")
        master \
            - Edge(color="brown", style="dashed") \
            - Redis("replica") \
            << Edge(label="collect") \
            << metrics
        grpcsvc >> Edge(color="brown") >> master

    with Cluster("Database HA"):
        master = PostgreSQL("users")
        master \
            - Edge(color="brown", style="dotted") \
            - PostgreSQL("slave") \
            << Edge(label="collect") \
            << metrics
        grpcsvc >> Edge(color="black") >> master

    aggregator = Fluentd("logging")
    aggregator \
        >> Edge(label="parse") \
        >> Kafka("stream") \
        >> Edge(color="black", style="bold") \
        >> Spark("analytics")

    ingress \
        >> Edge(color="darkgreen") \
        << grpcsvc \
        >> Edge(color="darkorange") \
        >> aggregator
```

![advanced web service with on-premise diagram colored](/img/advanced_web_service_with_on-premise_colored.png)