Architecture & Data Flow

Concord is a decentralized coordination engine. State is driven by an append-only event log, projected into local views, reconciled against container runtimes, and synchronized across nodes over an encrypted mesh.

Data Flow Diagrams

1. Workload Submission Flow

CLI / Go SDK
     │
     │ (1) POST /workload/submit
     │     (JSON Workload Spec)
     ▼
Unix IPC Server
(~/.config/concord/concord.sock)
     │
     │ (2) Record "workload.spec"
     │     Event
     ▼
Append-Only Journal
(journal.jsonl)
     │
     │ (3) Deterministic
     │     Projection
     ▼
bbolt KV Views
(Workloads, EventsByID, ByNode)

2. Local Workload Reconciliation & Execution Flow

bbolt KV Views (Desired State)
     │
     │ (4) Active Workload Specs
     ▼
Reconciler Loop
     │
     ├──► (5) Fetch Image
     │         │
     │         ▼
     │    Embedded OCI Registry
     │    (Zot localhost:8444)
     │
     └──► (6) Lifecycle Control
               │
               ▼
          Container Runtime
          (internal/cr)
               │
               ├──► cgroups (CPU/Mem)
               │
               ├──► runc (Namespaces)
               │
               ├──► Bridge & veth (concord0)
               │
               └──► Health Checker (/health)

3. Peer Discovery & WireGuard Mesh Flow

Node Discovery
     │
     ├──► mDNS (LAN Multicast)
     │         │
     ├──► SWIM Gossip (UDP :17946)
     │         │
     └──► DNS Server (SRV/A :15353)
               │
               ▼
     Peer Memberlist
               │
               │ (7) Exchange WG Keys & IPs
               ▼
     WireGuard Mesh (internal/cn)
     (Flat Encrypted P2P Overlay)

4. Cross-Node State & Image Replication Flow

[ Remote Node B ]
Transport Server & Registry
       │
       │ (8) mTLS Pull Events
       │ (10) P2P Image/Blob Sync
       │ (Over WireGuard Mesh)
       ▼
[ Local Node A ]
Peer Sync Loop (internal/peersync)
       │
       ├──► (9) Missing Events
       │         │
       │         ▼
       │    Local Journal (journal.jsonl)
       │         │
       │         ▼
       │    Local bbolt Views
       │         │
       │         ▼
       │    Reconciler ──► runc
       │
       └──► (10) Missing Blobs
                 │
                 ▼
            Embedded OCI Registry
            (localhost:8444)

Scheduling

In each connected segment, the node with the lowest UUID string is the leader. It assigns unassigned workloads to the peer with the fewest active workloads. When segments reunite, journals sync and state converges.