HASTE TiTiler Function API

HASTE TiTiler Function API#

A dynamic tile server deployed as an Azure Function, used by HASTE to serve Cloud Optimized GeoTIFF (COG) imagery and model inference results to the visualizer.

This deployment is adapted from the official TiTiler Azure deployment by Development Seed: github.com/developmentseed/titiler/tree/main/deployment/azure

What is TiTiler?#

TiTiler is an open-source dynamic tile server built on FastAPI. It reads geospatial raster files (COGs, STAC items, MosaicJSONs) directly from blob storage and serves XYZ map tiles on demand — no pre-tiling required.

HASTE uses it to render:

  • Pre- and post-event satellite imagery layers

  • Model inference output (predicted damage GeoTIFF) with colormap overlays

HASTE Modifications#

The upstream deployment provides a minimal Azure Function wrapper around the TiTiler FastAPI app. The app/__init__.py in this directory extends that with the following changes:

Feature flags#

The upstream unconditionally registers all routers. Here, each router is conditionally included based on ApiSettings:

if not api_settings.disable_cog:
    app.include_router(cog.router, prefix="/cog", ...)
if not api_settings.disable_stac:
    app.include_router(stac.router, prefix="/stac", ...)
if not api_settings.disable_mosaic:
    app.include_router(mosaic.router, prefix="/mosaicjson", ...)

Added middleware stack#

The upstream has no middleware. This deployment adds:

Middleware

Purpose

CORSMiddleware

Configurable allowed origins via api_settings.cors_origins

CompressionMiddleware

Response compression (excludes JPEG, PNG, JP2, WebP — already compressed)

CacheControlMiddleware

Cache headers via api_settings.cachecontrol; excludes /healthz

LoggerMiddleware + TotalTimeMiddleware

Request logging and timing (debug mode only)

LowerCaseQueryStringMiddleware

Normalizes query parameter casing (optional)

Added endpoints#

Two endpoints not present in the upstream minimal example:

  • GET /healthz — health check, returns {"ping": "pong!"}

  • GET / — HTML landing page via TiTiler’s built-in template

Exception handlers#

Explicit registration of TiTiler’s COG and Mosaic error codes:

add_exception_handlers(app, DEFAULT_STATUS_CODES)
add_exception_handlers(app, MOSAIC_STATUS_CODES)

Route prefix removed#

host.json sets routePrefix: "" to strip the default /api prefix that Azure Functions adds to all routes.

Routes#

Prefix

Description

/cog

Cloud Optimized GeoTIFF endpoints (tile, info, statistics, preview)

/stac

SpatioTemporal Asset Catalog endpoints

/mosaicjson

MosaicJSON mosaic endpoints

/tms

TileMatrixSets

/healthz

Health check

/

Landing page

Full interactive API docs are available at /docs when running.

Configuration#

TiTiler is configured via environment variables through ApiSettings (from titiler.application.settings):

Variable

Description

TITILER_API_DISABLE_COG

Set to true to disable COG endpoints

TITILER_API_DISABLE_STAC

Set to true to disable STAC endpoints

TITILER_API_DISABLE_MOSAIC

Set to true to disable MosaicJSON endpoints

TITILER_API_CORS_ORIGINS

Comma-separated list of allowed CORS origins

TITILER_API_CACHECONTROL

Cache-Control header value for tile responses

TITILER_API_DEBUG

Set to true to enable request logging middleware

TITILER_API_LOWER_CASE_QUERY_PARAMETERS

Set to true to normalize query param casing

Development Setup#

Prerequisites#

  • Azure CLI: https://docs.microsoft.com/en-us/cli/azure/install-azure-cli

  • Azure Functions Core Tools:

npm install -g azure-functions-core-tools@4 --unsafe-perm true

Running Locally#

func start

Deployment#

func azure functionapp publish {your-function-app-name} --python

For full deployment instructions see the upstream docs: https://docs.microsoft.com/en-us/azure/azure-functions/create-first-function-cli-python

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