Config Watcher

Notifies modules when infrastructure services change at runtime.

A MuxCore sidecar module that provides the config.watcher capability. Modules subscribe by capability string via WatchChanges (server-streaming gRPC) and receive events when a matching module registers or unregisters. Events are pushed by core or other modules through the ReportModuleChange admin RPC.

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How It Works

Module ──→ WatchChanges(stream) ──→ config-watcher
                                         ↑
Core/Admin ──→ ReportModuleChange ────────┘

WatchChanges (server-streaming)

Clients call WatchChanges with a capability string. The server keeps the stream open and pushes WatchChangesResponse events as they arrive.

ReportModuleChange (unary admin)

Core or another module calls ReportModuleChange with an event type, module ID, and capability. The module fans out the event to all watchers matching that capability (plus wildcard watchers watching "").

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Configuration

Environment Variables

Variable	Default	Description
CONFIG_WATCHER_GRPC_ADDR	:9611	gRPC listen address
MUXCORE_GRPC_ADDR	—	Core mesh address
MUXCORE_MODULE_ID	config-watcher	Module identity
MUXCORE_INSECURE_DISABLE_TLS	—	Disable TLS to core (true, dev only)

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Quick Start

# Build
make build

# Run against local core (dev mode)
export MUXCORE_INSECURE_DISABLE_TLS=true
./config-watcher --muxcore-mesh-addr localhost:9090

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Deployment

Docker

make docker
docker run -d --restart=unless-stopped \
  -e MUXCORE_GRPC_ADDR=core:9090 \
  ghcr.io/muxcore-media/config-watcher:latest

docker-compose

docker compose -f deploy/docker-compose.yml up

systemd

sudo cp deploy/systemd/muxcore-config-watcher.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now muxcore-config-watcher

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Development

make build   # compile
make test    # run tests
make lint    # golangci-lint
make fmt     # format code
make proto   # regenerate admin proto

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Implementation

• Registers with capability: "config.watcher"
• Declares contract ConfigWatcher (v0.4.0); serves gRPC (not in-process OnChange)
• Exposes two gRPC services:
  • ConfigWatcherService.WatchChanges (server-streaming)
  • ConfigWatcherAdminService.ReportModuleChange (unary)
• Event fan-out per capability with non-blocking channel sends

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License

GPL-3.0