Error map
522 Cloudflare Error 522: Connection Timed Out
Cloudflare · 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)
ERR_CONNECTION_TIMED_OUT: This site can’t be reached — example.com took too long to respond
The browser waited for the server but got no response — the server is down/unreachable, a firewall drops traffic, or DNS points t…
cURL error 28: Operation timed out after 30001 milliseconds with 0 bytes received
A PHP cURL (or Guzzle) request timed out before the remote server answered.
API Request Timed Out (ETIMEDOUT / ReadTimeout / timeout of 30000ms exceeded)
The client gave up waiting — either for the connection to open or for the response to arrive.
Error Domain=NSURLErrorDomain Code=-1001 "The request timed out."
The server didn’t respond within URLSession’s timeout (60 s default) — slow server, unreachable host on this network, or a stalle…
Cloudflare Error 521: Web Server Is Down
Cloudflare couldn’t connect to your origin — the connection was refused.
java.net.ConnectException: Connection refused
Nothing is listening at the host:port the Java client connected to.
java.util.concurrent.TimeoutException
A Future.get(timeout) or async operation didn’t complete in the allowed time.
FATAL: terminating connection due to idle-in-transaction timeout
A session opened a transaction and sat idle longer than idle_in_transaction_session_timeout.
Cloudflare Error 520: Web Server Returned an Unknown Error
Cloudflare connected to your origin, but the origin returned an empty, unknown or invalid response.
Cloudflare Error 524: A Timeout Occurred
Cloudflare connected to the origin, but the origin didn’t send an HTTP response within 100 seconds.
MySQL ERROR 2013 (HY000): Lost connection to MySQL server during query
The connection dropped mid-query — server crash/restart, timeouts, or a proxy cutting long queries.
API Gateway: {"message": "Endpoint request timed out"} (504 after 29 seconds)
The backend (usually Lambda) didn’t respond within API Gateway’s integration timeout (29 seconds by default for REST APIs).
Two steps away (36)
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 408 Request Timeout
The server closed the connection because the client took too long to send the complete request.
HTTP 499 Client Closed Request (Nginx)
Nginx-specific code logged when the client disconnected before the server finished responding.
PHP Fatal error: Maximum execution time of 30 seconds exceeded
The script ran longer than `max_execution_time` and PHP stopped it.
AWS Lambda: Task timed out after X seconds
The function ran longer than its configured timeout (default 3 seconds) and Lambda stopped it.
HTTP 504 Gateway Timeout
A proxy or gateway waited too long for the upstream server to respond and gave up.
SSL: CERTIFICATE_VERIFY_FAILED / unable to get local issuer certificate
The client couldn’t verify the server’s TLS certificate chain, so it refused the HTTPS connection.
Error: socket hang up / read ECONNRESET
The other side closed the TCP connection abruptly while your client was still using it.
MySQL ERROR 2006 (HY000): MySQL server has gone away
The connection to MySQL was closed — usually by a timeout or a packet larger than `max_allowed_packet`.
SQL Server: Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
The command ran longer than the client’s CommandTimeout (default 30 seconds).
ECS task stopped: CannotPullContainerError: pull image manifest has been retried ... / ref pull has been retried
The ECS task couldn’t pull its image — no network route to the registry, missing ECR permissions, or a wrong image tag.
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 Error 525: SSL Handshake Failed
Cloudflare couldn’t complete a TLS handshake with your origin (SSL mode Full / Full strict).
ConnectionRefusedError: [Errno 111] Connection refused
Nothing is listening on the host/port Python tried to connect to.
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.
java.net.UnknownHostException: api.example.com
DNS resolution failed for the hostname.
java.net.SocketException: Connection reset
The remote side closed the TCP connection abruptly while Java was reading or writing.
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.util.ConcurrentModificationException
A collection was modified while being iterated (even in a single thread).
HTTP 412 Precondition Failed
A conditional request header (If-Match, If-Unmodified-Since) didn’t match the current state of the resource.
MySQL ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction
MySQL detected a deadlock between two transactions and rolled one back.
ERROR: canceling statement due to statement timeout
A query ran longer than statement_timeout and PostgreSQL cancelled it.
ERROR: could not serialize access due to concurrent update
A REPEATABLE READ/SERIALIZABLE transaction conflicted with a concurrent one and must be retried.
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
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.
Cloudflare Error 526: Invalid SSL Certificate
With SSL mode Full (strict), the origin’s certificate is expired, self-signed, or doesn’t match the hostname.
ERROR: out of shared memory — HINT: You might need to increase max_locks_per_transaction.
A transaction took more locks than the lock table can hold — usually touching many tables/partitions at once.
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.
MySQL ERROR 2002 (HY000): Can't connect to local MySQL server through socket
The client couldn’t reach the MySQL server — it isn’t running, or the client is looking for the socket/port in the wrong place.
MySQL ERROR 1040 (08004): Too many connections
MySQL reached `max_connections` and refuses new clients.
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The MySQL JDBC driver couldn’t reach the database (or the connection dropped).
API Gateway {"message": "Internal server error"} 502 — Malformed Lambda proxy response
The Lambda behind an API Gateway proxy integration returned something that isn’t the required {statusCode, headers, body} shape,…
API Gateway 403: User is not authorized to access this resource with an explicit deny
An API Gateway authorizer (Lambda/Cognito) or resource policy denied the request.
SQS: The specified queue does not exist (AWS.SimpleQueueService.NonExistentQueue / QueueDoesNotExist)
The queue URL/name doesn’t exist in that region/account, or it was deleted (recently deleted names are blocked for 60 seconds).
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