# The UI > Orca's web UI: its pages and their JSON, the actions that start, backfill, resume, rerun and cancel runs, logins and sessions, a run's Dista timeline and instances, and links to the code. [magmalake](https://magmalake.dev/) [Orca](https://magmalake.dev/s/orca) `orca ui` serves pipelines, runs and datasets as web pages, from the same `orca` binary, on `127.0.0.1:8270` unless `ORCA_UI_ADDR` says otherwise. It holds no state: it reads the tables the scheduler and the runs write, connecting to Postgres per request, so it can run beside the scheduler or anywhere else that reaches the database. Nothing is fetched from elsewhere, so it works offline. ## Pages ``` ORCA_DATABASE_URL=postgresql:///orca ./build/orca ui curl -H 'Accept: application/json' http://127.0.0.1:8270/runs/7 ``` | Path | What it shows | | --- | --- | | / | pipelines, with their schedules, next runs and last runs, and runs per day over the last 30 days | | /pipelines/ | a pipeline's DAG, partitions, schedule, next runs, versions and runs, its code, and the forms to start a run, backfill a range, cancel its runs and pause it; a keyed one's keys, done, live and failed | | /pipelines//keys/ | one key of a keyed pipeline: its steps in every run it was in | | /runs | runs, newest first; ?pipeline=, ?status=, ?trigger= | | /runs/ | a run's DAG in its steps' colours, its steps and partitions, attempts, errors, reads and commits, its source and code, its timeline, machines and instances, and resume, rerun from a step and cancel | | /runs//attempts/ | an attempt's log, its last MiB, with its error | | /runs//timeline.json | the run's Dista timeline, for Perfetto | | /runs//driver.log | the run's driver output, as the scheduler kept it | | /runs//cluster/-.log | a head's or worker's output, from an EC2 run | | /datasets | every dataset with its writers and readers, and the graph of pipelines and datasets | | /datasets/ | a dataset's place in that graph, its snapshots, its rebuilds and the form to start one | | /datasets//snapshots/ | a snapshot's lineage, back and forward, as a graph and as tables | | /rebuilds/ | a rebuild's pipelines by level, with their runs | | /login, /logout | a session for the actions, as a cookie | Every path also answers JSON, to `Accept: application/json` or `?format=json`, built from the same rows, so a script and a person see the same thing. While a run or an attempt is going on, its page refreshes its DAG, steps or log every two seconds, and stops once it has ended. ## Actions | Action | What it does | | --- | --- | | Start | a queued run over the partitions entered, trigger ui | | Backfill | what orca backfill does: a queued run for each partition without one, and with and what is ticked, the done ones too | | Resume | a failed, cancelled or stalled run queued again, to resume at what hasn't succeeded; a run whose code has changed asks for confirmation first | | Rerun from a step | a new run, trigger rerun, with the steps before the chosen one copied from the old run, so only it and what follows run | | Cancel | a queued or failed run cancelled at once; a running one stops before its next attempt, and the attempt already going finishes | | Pause, Unpause | on a pipeline's page: what orca pause and orca unpause do | | Cancel queued runs | on a pipeline's page: what orca cancel does, over @all or the partitions entered | | Rebuild | on a dataset's page: what orca rebuild does, over the partitions entered | The UI never starts a pipeline binary. An action writes rows in Postgres, and the scheduler starts the queued runs on its next tick, within `max_runs`, so the UI does nothing without a scheduler running. It binds to localhost unless told otherwise, and refuses a `POST` whose `Origin`, or `Referer` without one, isn't its own, so another site's page can't post to it through a browser. ## Login Anyone who can reach the UI can read it. Its actions need a login once there's a user, or with `ORCA_UI_LOGIN=required` before there is one: ``` ./build/orca user add alice # reads the password from standard input ./build/orca user list ./build/orca user remove alice # and ends their sessions ``` Passwords are kept as bcrypt hashes made by Postgres. A login is a session cookie, `HttpOnly` and `SameSite=Strict`, and `Secure` with `ORCA_UI_SECURE_COOKIES=1` behind HTTPS. Every action is recorded with its user and shown on its run's page, and so is every failed login: after 5 for one name, or 20 from one address, in 15 minutes, `/login` answers 429 without checking the password. Behind a proxy, `ORCA_UI_TRUST_PROXY=1` takes the address from `X-Forwarded-For`. ## A run's page A run with Dista tasks draws its timeline: one lane per worker, each task a bar coloured by its function. With `ORCA_UI_URL` set to the UI's public address, an Open in Perfetto link opens the full trace there. Its [machine metrics](https://magmalake.dev/s/orca/docs/run#metrics) are drawn under its steps. A run on EC2 lists its instances, with the number of workers over the run, why each instance ended, and each one's log. The step names, the pipeline and its Dista tasks link to their code ([versions and code links](https://magmalake.dev/s/orca/docs/build#versions)), in a new tab, and the headings link to these docs (`ORCA_DOCS_URL` changes where). [A magmalake project](https://magmalake.dev/) Apache 2.0 · © 2026 Marius Seritan