From 38da8933c3577f86fa1d4cd445142834849b6929 Mon Sep 17 00:00:00 2001
From: Stephanie Gredell <s.raide@gmail.com>
Date: Wed, 18 Jun 2025 00:01:20 -0700
Subject: [PATCH] Add database node

---
 internal/simulation/databasenode.go | 81 +++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 internal/simulation/databasenode.go

diff --git a/internal/simulation/databasenode.go b/internal/simulation/databasenode.go
new file mode 100644
index 0000000..0ed271b
--- /dev/null
+++ b/internal/simulation/databasenode.go
@@ -0,0 +1,81 @@
+package simulation
+
+type DatabaseNode struct {
+	ID               string
+	Label            string
+	Replication      int
+	CurrentLoad      int
+	Queue            []*Request
+	Replicas         []*DatabaseNode
+	Alive            bool
+	Targets          []string
+	output           []*Request
+	replicationQueue []*Request
+}
+
+func (n *DatabaseNode) GetID() string        { return n.ID }
+func (n *DatabaseNode) Type() string         { return "database" }
+func (n *DatabaseNode) IsAlive() bool        { return n.Alive }
+func (n *DatabaseNode) GetQueue() []*Request { return n.Queue }
+
+func (n *DatabaseNode) Tick(tick int) {
+	if len(n.Queue) == 0 {
+		return
+	}
+
+	maxProcessPerTick := 3
+	processCount := min(len(n.Queue), maxProcessPerTick)
+
+	queue := n.Queue
+	n.Queue = n.Queue[:0]
+
+	for i := 0; i < processCount; i++ {
+		req := queue[i]
+
+		if req.Type == "READ" {
+			req.LatencyMS += 20
+			req.Path = append(req.Path, n.ID)
+			n.output = append(n.output, req)
+		} else {
+			req.LatencyMS += 50
+			req.Path = append(req.Path, n.ID)
+
+			// Replicate to replicas
+			for _, replica := range n.Replicas {
+				replicationReq := &Request{
+					ID:        req.ID + "-repl",
+					Timestamp: req.Timestamp,
+					LatencyMS: req.LatencyMS + 5,
+					Origin:    req.Origin,
+					Type:      "REPLICATION",
+					Path:      append(append([]string{}, req.Path...), "->"+replica.ID),
+				}
+				n.replicationQueue = append(n.replicationQueue, replicationReq)
+			}
+
+			n.output = append(n.output, req)
+		}
+	}
+
+	// Apply queuing penalty if overloaded
+	if len(n.Queue) > 10 {
+		for _, req := range n.Queue {
+			req.LatencyMS += 10
+		}
+	}
+}
+
+func (n *DatabaseNode) Receive(req *Request) {
+	if req == nil {
+		return
+	}
+	req.LatencyMS += 2 // DB connection overhead
+	n.Queue = append(n.Queue, req)
+}
+
+func (n *DatabaseNode) Emit() []*Request {
+	out := append(n.output, n.replicationQueue...)
+	n.output = n.output[:0]
+	n.replicationQueue = n.replicationQueue[:0]
+	return out
+}