Error map
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WordPress · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (7). 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 (7)
WordPress: Error establishing a Redis connection (object cache)
The persistent object cache drop-in (object-cache.php) can’t connect to Redis, so the whole site fails.
WooCommerce: There was an error processing your order. Please check for any charges in your payment method / Error processing checkout. Please try again.
Checkout failed server-side — payment gateway error, nonce/session issue from caching, or a PHP error from a plugin hook.
HTTP 304 Not Modified
The cached copy is still valid, so the server sends no body and the client reuses its cache.
Cloudflare not caching: cf-cache-status DYNAMIC / BYPASS / MISS every time
Cloudflare isn’t caching the response — HTML isn’t cached by default, and cookies or Cache-Control headers from the origin preven…
WordPress login: Error: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.
WordPress’s test cookie wasn’t returned on login — often a siteurl/home or domain mismatch, caching of wp-login.php, or headers a…
Cloudflare Error 1200: Cache connection limit
Too many requests are queued at Cloudflare for the origin — the origin is slow and connections pile up.
HTTP 412 Precondition Failed
A conditional request header (If-Match, If-Unmodified-Since) didn’t match the current state of the resource.
Two steps away (21)
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.
ReplyError: NOAUTH Authentication required.
The Redis server requires a password (or ACL user) but the client didn’t authenticate.
WRONGTYPE Operation against a key holding the wrong kind of value
A Redis command was used on a key of a different type (e.g. HGET on a string key).
Webhook delivery failed (endpoint returned non-2xx / timed out)
The provider tried to send a webhook to your endpoint but didn’t get a timely 2xx response, so it marks the delivery failed and r…
API Error: a similar object exists in test mode, but a live mode key was used
You’re using an ID, key or URL from one environment (test/sandbox) with credentials from another (live/production), or vice versa.
WordPress: 404 Not Found on every page except the homepage (permalinks / .htaccess / Nginx rules)
Pretty permalinks aren’t being routed to index.php — .htaccess is missing/ignored (Apache) or Nginx lacks try_files.
HTTP 301 Moved Permanently
The resource has a new permanent URL; clients and search engines should use the address in the Location header from now on.
HTTP 200 OK (but something is still wrong)
The request succeeded at the HTTP level — yet the page is blank, the data is wrong, or an error is hidden inside the response bod…
HTTP 428 Precondition Required
The server requires a conditional request (If-Match / If-Unmodified-Since) to prevent lost updates, and you didn’t send one.
HTTP 504 Gateway Timeout
A proxy or gateway waited too long for the upstream server to respond and gave up.
Cloudflare Error 524: A Timeout Occurred
Cloudflare connected to the origin, but the origin didn’t send an HTTP response within 100 seconds.
ERROR: canceling statement due to statement timeout
A query ran longer than statement_timeout and PostgreSQL cancelled it.
Warning: Cannot modify header information - headers already sent
You called `header()`, `setcookie()` or `session_start()` after output had already been sent to the browser.
HTTP 431 Request Header Fields Too Large
The request headers — almost always cookies — exceed the server’s size limit.
WordPress: ERR_TOO_MANY_REDIRECTS / redirected you too many times on wp-admin or the whole site
WordPress and the server/proxy keep redirecting to each other — usually siteurl/home mismatch (http vs https, www vs non-www) or…
HTTP 503 Service Unavailable
The server is temporarily unable to handle the request — overloaded, in maintenance, or has no healthy backends.
Performance: N+1 query problem (one query per row in a loop)
Code runs one query to load a list, then one more query per item — hundreds of queries per page.
Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. All pooled connections were in use and max pool size was reached.
The application’s connection pool was exhausted — all connections busy or leaked.
HTTP 409 Conflict
The request conflicts with the current state of the resource — e.g. a duplicate or an edit based on an outdated version.
java.lang.InterruptedException (sleep interrupted)
A blocked thread (sleep, wait, join, queue take) was interrupted by another thread.
java.util.concurrent.TimeoutException
A Future.get(timeout) or async operation didn’t complete in the allowed time.
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