Configuration

All runtime behaviors are controlled via environment variables defined in the vars block of wrangler.jsonc or via the Cloudflare Dashboard. The script includes hardcoded fallback defaults; you only need to assign a variable if you intend to override the default value.

Environment Variables Reference

Variable	Default Value	Description
UPSTREAM_URLS	https://dns.google/dns-query,https://dns11.quad9.net/dns-query	Comma-separated list of upstream DoH resolvers.
DOH_PATH	/dns-query	The listening URI path for DoH requests.
DOH_CONTENT_TYPE	application/dns-message	Expected MIME type for DNS payloads.
ROOT_CONTENT	(Generated HTML)	Custom HTML content to serve at the / path.
ROOT_CONTENT_TYPE	text/html; charset=utf-8	MIME type for the root path response.
ROOT_CACHE_TTL	86400	Time-to-live (in seconds) for the root landing page.
MAX_CACHEABLE_BYTES	65536	Maximum byte size for caching a DNS response.
MAX_POST_BODY_BYTES	8192	Maximum byte size allowed for incoming POST requests.
FETCH_TIMEOUT_MS	2500	Timeout limit (in milliseconds) for upstream fetch operations.
MAX_RETRIES	2	Maximum number of retry attempts for failed upstream requests.
DEFAULT_POSITIVE_TTL	60	Default TTL (in seconds) applied to successful resolutions if none is provided.
DEFAULT_NEGATIVE_TTL	15	Default TTL (in seconds) applied to NXDOMAIN or failed resolutions.
FALLBACK_ECS_IP	119.29.29.0	Default IP address injected for EDNS Client Subnet if the client IP is unresolvable.
CF_CACHE_WRITE_THRESHOLD	500	Probability threshold (out of 10000) for writing responses to the Cloudflare global cache.
GLOBAL_WRITE_COOLDOWN_MS	300000	Minimum interval (in milliseconds) required between global cache writes for the same key.
GLOBAL_WRITE_PER_MINUTE_LIMIT	200	Maximum number of global cache writes allowed per minute across the isolate.
GLOBAL_CACHE_NAMESPACE	https://dohflare.local/cache/	The dummy URL namespace used for isolating objects in the Cloudflare Cache API.
HOT_WINDOW_MS	60000	Time window (in milliseconds) to track request frequency for L1 hot cache promotion.
HOT_HIT_THRESHOLD	20	Minimum number of hits within the hot window to trigger an immediate global cache write.
STALE_WINDOW_FACTOR	0.5	Multiplier applied to the TTL to determine the acceptable stale-while-revalidate window.
EXTREME_STALE_FALLBACK_MS	86400000	Maximum time (in milliseconds) to serve stale cache data if all upstream requests fail.
JITTER_PCT	10	Percentage of deterministic jitter applied to TTLs to mitigate cache stampedes.