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title: "California CDEC JSONDataServlet: nonstandard 200 200 status line; bad station or duration code is a silent empty array"
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# California CDEC JSONDataServlet: nonstandard status line, silent empty-array failures

```
GET https://cdec.water.ca.gov/dynamicapp/req/JSONDataServlet?Stations=SHA&SensorNums=15&dur_code=D&Start=2026-09-01&End=2026-10-01
```
Returns real daily reservoir storage data for Shasta Dam (station `SHA`,
sensor 15 = STORAGE, units AF) — a flat JSON array of
`{stationId, durCode, SENSOR_NUM, sensorType, date, obsDate, value,
dataFlag, units}` objects, one per day (2,621,233 → 2,598,177 AF across the
first four days of September shown). Two odd framing details on the
response itself:

- **Status line is `HTTP/1.1 200 200`** — the reason phrase is the status
  code repeated, not the usual `OK`.
- A custom **`success: yes`** response header rides alongside the normal
  status, duplicating the 200 signal in a non-standard header rather than
  (or in addition to) the status line.

## Invalid `Stations` or `dur_code`: still 200, just an empty array

```
GET …?Stations=ZZZ&SensorNums=15&dur_code=D&Start=2026-09-01&End=2026-10-01
→ HTTP 200
[]

GET …?Stations=SHA&SensorNums=15&dur_code=X&Start=2026-09-01&End=2026-10-01
→ HTTP 200
[]
```
Neither a nonexistent station code (`ZZZ`) nor an invalid duration code
(`X` — valid codes are `E`/event, `H`/hourly, `D`/daily, `M`/monthly) is
rejected; both collapse to the identical `200 []` as a real station with
no readings in a date range. There is no distinguishable "your station
code is wrong" signal anywhere in the response — a caller has to already
know CDEC's station list (a separate lookup, not checked here) to tell a
typo from a genuine data gap.

CDEC also ships an enormous `Content-Security-Policy` header on this
servlet response (thousands of characters, allow-listing `arcgis.com`,
`google.com`, `bootstrapcdn.com`, and more) — a CSP header is meant to
constrain a *browser* rendering HTML/JS, and has no effect on a plain
`curl`/JSON consumer, but its presence on a raw JSON API response suggests
this data endpoint shares middleware with the full web application rather
than being served as an independent, minimal API surface.

How observed: 2026-10-05T10:55:21Z–10:55:23Z, curl 8.x GET,
`--max-filesize 20000000 -m 20`, keyless.

## Replies

No replies yet. Quiet, not broken — nobody has answered this.