uopi

A web-based HMI (Human-Machine Interface) for monitoring and controlling EPICS-based scientific and industrial control systems.

uopi runs as a single portable binary with no runtime dependencies. Point any browser at it — including over an SSH tunnel — and you get a full drag-and-drop HMI builder and live data viewer.

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Features

Feature	Details
Live data	EPICS Channel Access (CA) / PVAccess and user-defined synthetic signals
HMI editor	Drag-and-drop widgets, resize, align/distribute, undo/redo, saved as XML
Widget library	Text view/label, gauge, LED, multi-LED, bar, set-point control, button, image, link, plots
Plot types	Time-series (uPlot), FFT, waterfall, histogram, bar chart, logic analyser
Plot panels	Dedicated chart panels with a recursive split layout (tmux/IDE-style) where plots fill the viewport
Panel logic	In-editor node-graph flow editor (triggers → actions, dialogs) that runs client-side in view mode
Control logic	Server-side always-on flow graphs with cron/alarm triggers and Lua blocks
Configuration manager	Versioned configuration sets (typed signal schemas, grouped) and instances (values) with validation, array/CSV editing, apply-to-signals, and JSON import/export
Version history & diff	Git-style history for panels, synthetic signals, control logic and config sets/instances: view, fork, promote any revision, with unified / side-by-side diff
Local variables	Panel-scoped state variables for set-points, toggles and counters used by logic
Historical data	EPICS Archive Appliance integration via REST; time range picker in UI
Synthetic signals	Compose, filter, and transform signals via a wizard or visual node-graph editor (gain, offset, moving average, lowpass, highpass, derivative, integral, clamp, formula); panel/user/global visibility scopes
Access control	Identity via trusted proxy header; per-user global level (write/read-only/no-access); per-panel ownership + sharing; nested folders; optional logic-editor allowlist
Multi-client	Subscriptions are multiplexed — N clients share one upstream connection per signal
Signal discovery	Filter/search, CSV import, manual add, Channel Finder proxy
Observability	Prometheus-format metrics at /metrics
Single binary	Frontend assets embedded at build time — no web server needed

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Quick Start

Prerequisites

• Go 1.22+ — the only build dependency (the frontend is bundled by a pure-Go esbuild wrapper)
• EPICS Base (libca) — only required for the epics build tag; the stub and synthetic data sources work without it

Build

# Full build — bundles the frontend then compiles the binary
make all

The binary is written to dist/uopi.

Run

./dist/uopi                    # uses default config (stub data source only)
./dist/uopi --config uopi.toml # explicit config file

Then open http://localhost:8080 in your browser.

SSH tunnel example:

ssh -L 8080:localhost:8080 user@controlhost
# then open http://localhost:8080 locally

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Configuration

Create uopi.toml (all fields are optional — shown values are defaults):

[server]
listen      = ":8080"
storage_dir = "./interfaces"  # where interface XML, ACL and logic data are stored

# Identity & access control (all optional)
trusted_user_header = ""      # HTTP header carrying the proxy-authenticated user
default_user        = ""      # identity used when the header is absent (LAN/dev)
# logic_editors     = []      # restrict who may edit panel/control logic (users or groups)

# [[server.blacklist]]        # downgrade a user: level = "readonly" or "noaccess"
# user = "guest"
# level = "readonly"

# [[groups]]                  # named user sets, referenced by panel sharing
# name    = "operators"
# members = ["alice", "bob"]

[datasource.epics]
enabled           = false    # requires build with -tags epics
ca_addr_list      = ""       # overrides EPICS_CA_ADDR_LIST if non-empty
archive_url       = ""       # EPICS Archive Appliance base URL, e.g. http://archiver:17665
channel_finder_url = ""      # EPICS Channel Finder base URL (optional)

[datasource.synthetic]
enabled = true

All settings can be overridden with environment variables using the UOPI_ prefix and double underscores for nesting:

UOPI_SERVER_LISTEN=":9090" UOPI_DATASOURCE_EPICS_ENABLED=true ./dist/uopi

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Building with EPICS Support

The EPICS data source uses CGo bindings to libca. First set up the EPICS environment variables, then:

export EPICS_BASE=/path/to/epics/base
export CGO_CFLAGS="-I$EPICS_BASE/include -I$EPICS_BASE/include/os/Linux"
export CGO_LDFLAGS="-L$EPICS_BASE/lib/linux-x86_64 -lca -lCom"

make backend-epics

Then enable it in uopi.toml:

[datasource.epics]
enabled = true

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API

The REST API is available under /api/v1. Key endpoints:

Method	Path	Description
GET	/api/v1/datasources	List registered data sources
GET	/api/v1/signals?ds=<name>	List signals for a data source
GET	/api/v1/signals/search?q=<query>	Search signals across all sources
GET	/api/v1/channel-finder?q=<query>	Proxy to EPICS Channel Finder
GET/POST	/api/v1/interfaces	List or create HMI interfaces
GET/PUT/DELETE	/api/v1/interfaces/{id}	Read, update, or delete an interface
POST	/api/v1/interfaces/{id}/clone	Duplicate an interface
POST	/api/v1/interfaces/reorder	Reorder panels / move them between folders
GET/PUT	/api/v1/interfaces/{id}/acl	Read or set a panel's sharing rules
GET/POST	/api/v1/folders	List or create panel folders
PUT/DELETE	/api/v1/folders/{id}	Rename/reparent or delete a folder
GET/POST/DELETE	/api/v1/synthetic	Manage synthetic signal definitions
GET/POST	/api/v1/controllogic	List or create server-side control-logic graphs
GET/PUT/DELETE	/api/v1/controllogic/{id}	Read, update, or delete a control-logic graph
GET/POST	/api/v1/config/sets	List or create configuration sets (schemas)
GET/PUT/DELETE	/api/v1/config/sets/{id}	Read, update, or delete a config set
GET/POST	/api/v1/config/instances	List or create configuration instances (values)
GET/PUT/DELETE	/api/v1/config/instances/{id}	Read, update, or delete a config instance
POST	/api/v1/config/instances/{id}/apply	Write an instance's values to their target signals
GET	/api/v1/config/{sets|instances}/diff	Structural diff between two revisions
GET	/api/v1/{interfaces|synthetic|controllogic|config/sets|config/instances}/{id}/versions	List revisions; …/{version} fetches one
POST	…/{id}/versions/{v}/promote	Promote a revision to current
POST	…/{id}/versions/{v}/fork	Fork a revision into a new document
GET	/api/v1/me	Caller identity, access level, groups, logic-edit permission
GET	/api/v1/usergroups	List configured users and groups (for sharing)
GET	/metrics	Prometheus-format server metrics
GET	/healthz	Health check

WebSocket live data is at ws://<host>/ws. See docs/TECHNICAL_SPEC.md for the message protocol.

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Development

# Build frontend only (output → web/dist/)
make frontend

# Build backend only (frontend must already be built)
make backend

# Run the server directly without a binary (uses stub data source)
go run ./cmd/uopi

# Run all tests
make test

# Run tests with race detector
make race

# Run benchmarks
make bench

# Static analysis
make lint

# Clean build artefacts
make clean

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Observability

The /metrics endpoint exposes Prometheus-format counters and gauges:

uopi_uptime_seconds          — seconds since start
uopi_ws_connections          — current open WebSocket connections
uopi_signal_subscriptions    — current unique upstream signal subscriptions
uopi_ws_messages_in_total    — total messages received from clients
uopi_ws_messages_out_total   — total messages sent to clients
uopi_write_ops_total         — total signal write operations
uopi_history_requests_total  — total historical data requests

Scrape with any Prometheus-compatible tool or view directly in the browser.

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Docs

Document	Description
docs/FUNCTIONAL_SPEC.md	User-facing feature specification
docs/TECHNICAL_SPEC.md	Architecture, WebSocket protocol, API design
docs/WORK_PLAN.md	Phased development plan with milestones

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Release

Releases are built with goreleaser:

goreleaser release --clean

See .goreleaser.yaml. Note that release binaries are built without EPICS support (CGO_ENABLED=0) for maximum portability. Build from source with -tags epics for CA connectivity.

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License

TBD