Error map
nginx: host not found in upstream Nginx: nginx: [emerg] host not found in upstream "app" in /etc/nginx/conf.d/default.conf:5
Nginx / Apache · layer 3, Edge & web server
Centre: this error. First ring: errors it is linked with (12). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (12)
cURL error 6: Could not resolve host: api.example.com
PHP cURL couldn’t resolve the hostname via DNS.
Cloudflare Error 1014: CNAME Cross-User Banned
Your DNS CNAME points to a hostname in another Cloudflare account, which Cloudflare blocks by default for security.
ping: google.com: Temporary failure in name resolution
The Linux host can’t resolve domain names — no working DNS server is configured or reachable.
Cloudflare Error 1000: DNS points to prohibited IP
A proxied DNS record points at a Cloudflare IP address, creating a loop.
Cloudflare Error 1003: Direct IP access not allowed
The request went to a Cloudflare IP address directly (or with a Host header for a domain not on Cloudflare).
sudo: unable to resolve host <hostname>: Name or service not known
The machine’s hostname isn’t in /etc/hosts (or DNS), so sudo prints this warning — usually after changing the hostname.
Cloudflare Error 523: Origin is unreachable
Cloudflare can’t find a network route to your origin server — the DNS record points to a wrong/unroutable IP or the origin networ…
Cloudflare Error 1001: DNS resolution error
Cloudflare received the request but the hostname isn’t set up on Cloudflare (or the domain was just added and not active yet).
HTTP 502 Bad Gateway
A proxy or gateway (Nginx, load balancer, CDN) got an invalid response — or no response — from the upstream server behind it.
Cloudflare HTTP 530 (with Error 1016 Origin DNS error / 1033 tunnel error)
Cloudflare returns 530 together with a 1xxx error; the 1xxx code (usually 1016 or 1033) tells you the real cause.
Cloudflare Error 1002: DNS points to Prohibited IP / Restricted
A record points to a private, reserved or Cloudflare IP that Cloudflare won’t proxy to.
Cloudflare Error 1018: Could not find host
The hostname isn’t found on Cloudflare — the zone was recently added/removed, or the record doesn’t exist yet.
Two steps away (36)
Error: getaddrinfo ENOTFOUND host / Name or service not known
DNS lookup for the hostname failed — the name is wrong, doesn’t exist, or this machine can’t resolve it.
fatal: unable to access 'https://github.com/…': Could not resolve host: github.com
DNS lookup for the Git host failed from this machine.
java.net.UnknownHostException: api.example.com
DNS resolution failed for the hostname.
Cloudflare Error 1004: Host Not Configured to Serve Web Traffic
The DNS record was just created or changed and Cloudflare hasn’t propagated it yet — or Spectrum/non-HTTP ports are involved.
Cloudflare Error 1016: Origin DNS error
Cloudflare can’t resolve the origin hostname your DNS record points to (usually a CNAME target).
Cloudflare Error 1023: Could not find host
Cloudflare can’t find the host — typically a zone that’s inactive or a custom hostname/SSL for SaaS not set up.
npm ERR! code ENOTFOUND — request to https://registry.npmjs.org/x failed, reason: getaddrinfo ENOTFOUND registry.npmjs.org
npm couldn’t resolve the registry hostname.
dial tcp: lookup registry-1.docker.io: no such host / Temporary failure in name resolution during docker build
DNS isn’t working for the Docker daemon or inside build containers, so pulls and package downloads fail.
Error: Failed to download metadata for repo 'appstream' (dnf / yum)
dnf/yum can’t fetch a repository’s metadata — the mirror is unreachable, the repo URL is dead (CentOS 8 EOL), or there’s a DNS/pr…
HTTP 413 Content Too Large (Request Entity Too Large)
The request body is bigger than the server is willing to accept — usually a file upload over the configured limit.
WordPress: Error Establishing a Database Connection
WordPress can’t connect to its MySQL/MariaDB database with the credentials in wp-config.php, or the database server is down.
hint: You have divergent branches and need to specify how to reconcile them.
Git 2.27+ asks you to choose merge, rebase or fast-forward-only when local and remote both have new commits.
Cloudflare Error 1013: HTTP hostname and TLS SNI hostname mismatch
The TLS SNI (the hostname used for the certificate) differs from the HTTP Host header in the same request.
Cloudflare Error 1034: Edge IP Restricted
The DNS record points to a Cloudflare IP not assigned to your zone — typically an A record pointing to an old Cloudflare IP or an…
Cloudflare Error 1035 / 1036: Invalid request rewrite (invalid URI path / query string)
A Transform Rule (URL rewrite) produced an invalid path or query string.
user is not in the sudoers file. This incident will be reported.
Your account isn’t allowed to use sudo.
API Error: Invalid or unsupported API version
The API version you requested — in the URL, a header or the SDK config — doesn’t exist or has been retired.
API Error: Feature not enabled for this account (feature_not_enabled / not available on your plan)
The endpoint or option exists, but your account, plan, region or project hasn’t been granted access to it.
Cloudflare Error 521: Web Server Is Down
Cloudflare couldn’t connect to your origin — the connection was refused.
Cloudflare Error 522: Connection Timed Out
Cloudflare’s TCP connection to your origin timed out — the origin didn’t answer at all.
Cloudflare Error 1033: Argo Tunnel error (Cloudflare Tunnel not connected)
The hostname routes to a Cloudflare Tunnel, but no healthy cloudflared connector is running for it.
net::ERR_NAME_NOT_RESOLVED (This site can't be reached — server IP address could not be found)
DNS couldn’t resolve the hostname in the browser.
ACM certificate stuck in Pending validation
ACM is waiting to see the DNS (or email) validation record — it wasn’t created, was created in the wrong DNS zone, or has a typo.
DNS not working inside a Kubernetes pod (could not resolve host / nslookup: can't resolve)
Pods can’t resolve service names or external hosts — CoreDNS is down, blocked by NetworkPolicy, or the upstream resolver fails.
Error: connect ECONNREFUSED 127.0.0.1:5432
Nothing is listening at that host:port — the target service is down or you’re connecting to the wrong address.
HTTP 407 Proxy Authentication Required
A proxy between you and the server requires credentials before it will forward your request.
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
cloudflared: Unable to reach the origin service. The service may be down or it may not be responding to traffic from cloudflared (502)
The tunnel is connected, but cloudflared can’t reach your local service at the address in the ingress rule.
Chrome: This site can’t be reached — server IP address could not be found. DNS_PROBE_FINISHED_NXDOMAIN
The DNS server answered that the domain name does not exist (NXDOMAIN) — a typo, an expired or unregistered domain, a missing DNS…
Chrome: No internet — DNS_PROBE_FINISHED_NO_INTERNET (DNS probe finished, no internet)
Chrome’s built-in DNS probe could not reach any DNS server, so the device effectively has no working internet or DNS.
Cloudflare Error 1037: Invalid rewrite rule (failed to evaluate expression)
A rewrite rule’s dynamic expression failed at runtime — for example a function received a value of the wrong type or a missing fi…
Cloudflare DNS: An A, AAAA, or CNAME record with that host already exists (code 81053)
Cloudflare won’t create the record because another record of a conflicting type already uses that name.
InvalidOperationException: The ConnectionString property has not been initialized
The database connection was opened with an empty connection string — the configuration key wasn’t found.
InvalidOperationException: No database provider has been configured for this DbContext
EF Core created a DbContext without UseSqlServer/UseNpgsql/UseSqlite — typically because the context was newed up manually or reg…
WordPress site shows "Index of /" (directory listing instead of the site)
The web server isn’t using index.php as the directory index, or index.php is missing — so it lists files instead of running WordP…
LLM API: The model `x` does not exist or you do not have access to it (model_not_found / not_found_error)
The model name is wrong, deprecated/retired, or not available to your account/region.
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