zfin-server

HTTP data service backed by zfin's financial data providers. Serves cached market data over HTTP for two consumers:

1. LibreCalc spreadsheets — trailing returns via WEBSERVICE/FILTERXML
2. zfin CLI/TUI — raw SRF cache files as an L1 data cache

Quick start

# Set API keys (same as zfin)
export TWELVEDATA_API_KEY=...
export POLYGON_API_KEY=...

# Start the server
zig build run -- serve --port=8080

# In another terminal
curl http://localhost:8080/AAPL/returns
curl http://localhost:8080/AAPL/returns?fmt=xml

Endpoints

Route	Content-Type	Description
GET /	text/html	Landing page
GET /help	text/plain	Endpoint documentation
GET /symbols	application/json	List of tracked symbols
GET /:symbol/returns	application/json	Trailing 1/3/5/10yr returns + volatility
GET /:symbol/returns?fmt=xml	application/xml	Same, XML for LibreCalc
GET /:symbol/quote	application/json	Latest quote
GET /:symbol/candles	application/x-srf	Raw SRF cache file
GET /:symbol/dividends	application/x-srf	Raw SRF cache file
GET /:symbol/earnings	application/x-srf	Raw SRF cache file
GET /:symbol/options	application/x-srf	Raw SRF cache file

LibreCalc usage

=FILTERXML(WEBSERVICE("http://localhost:8080/AAPL/returns?fmt=xml"), "//trailing1YearReturn")

XML response format:

<returns>
  <ticker>AAPL</ticker>
  <returnDate>2026-03-07</returnDate>
  <trailing1YearReturn>12.34000</trailing1YearReturn>
  <trailing3YearReturn>8.56000</trailing3YearReturn>
  <trailing5YearReturn>15.78000</trailing5YearReturn>
  <trailing10YearReturn>22.10000</trailing10YearReturn>
  <volatility>18.50000</volatility>
</returns>

Cache refresh

Use cron to keep the cache warm for all symbols in your portfolio:

# Refresh all portfolio symbols daily at 5pm ET (after market close)
0 17 * * 1-5 cd /path/to/workdir && ZFIN_PORTFOLIO=portfolio.srf zfin-server refresh

The candle cache TTL is 23h45m (not a full 24h), providing a 15-minute jitter buffer so daily cron runs at the same time always see stale data and trigger a fresh fetch. Dividend and earnings TTLs are 14 and 30 days respectively.

The refresh command reads the portfolio SRF file (defaults to portfolio.srf in the current directory if ZFIN_PORTFOLIO is not set), extracts all stock and watch symbols, and fetches candles, dividends, and earnings for each.

Building

Requires Zig 0.15.2.

zig build        # build
zig build test   # run tests
zig build run -- serve --port=8080

Configuration

All configuration is via environment variables:

Variable	Required	Description
TWELVEDATA_API_KEY	Yes	TwelveData API key
POLYGON_API_KEY	No	Polygon API key
FINNHUB_API_KEY	No	Finnhub API key
ALPHAVANTAGE_API_KEY	No	Alpha Vantage API key
ZFIN_PORTFOLIO	No	Path to portfolio SRF (default: portfolio.srf)
ZFIN_CACHE_DIR	No	Cache directory (default: ~/.cache/zfin)

License

MIT