Error map
could not connect PostgreSQL: could not connect to server / connection refused — Is the server running on host and accepting TCP/IP connections?
PostgreSQL · layer 5, Data
Centre: this error. First ring: errors it is linked with (11). 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 (11)
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.
PostgreSQL: FATAL: password authentication failed for user
PostgreSQL rejected the password for that role, or pg_hba.conf requires a different auth method.
FATAL: too many connections for role "x"
The role reached its per-role CONNECTION LIMIT (often set by hosting providers or free tiers).
Error: P1001: Can't reach database server at `host`:`5432`
Prisma couldn’t connect to the database in DATABASE_URL.
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) connection to server … failed
SQLAlchemy’s DB driver raised an operational error — connection failures, lost connections or locked SQLite databases.
FATAL: sorry, too many clients already / remaining connection slots are reserved for non-replication superuser connections
PostgreSQL reached max_connections.
server closed the connection unexpectedly — This probably means the server terminated abnormally before or while processing the request.
The connection to PostgreSQL dropped — the server restarted/crashed, a proxy/firewall killed an idle connection, or the backend w…
server does not support SSL, but SSL was required / no pg_hba.conf entry … no encryption
The client and server disagree about SSL — the client requires it but the server doesn’t offer it, or the server requires it and…
FATAL: database "x" does not exist
The connection names a database that isn’t on that server.
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.
SequelizeConnectionRefusedError: connect ECONNREFUSED 127.0.0.1:5432
Sequelize couldn’t connect to the database server.
Two steps away (27)
MySQL ERROR 1045 (28000): Access denied for user
MySQL rejected the login — wrong password, wrong user/host combination, or the user doesn’t exist.
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`.
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.
PostgreSQL: ERROR: relation "x" does not exist
The table/view isn’t found — missing migration, wrong schema, or a case-sensitive quoted name.
PostgreSQL: ERROR: permission denied for table / schema public
The role is connected but lacks privileges on that table or schema — very common after PostgreSQL 15 removed CREATE on the public…
MySQL ERROR 1130 (HY000): Host 'x' is not allowed to connect to this MySQL server
No MySQL account exists for the host you’re connecting from.
MySQL ERROR 1040 (08004): Too many connections
MySQL reached `max_connections` and refuses new clients.
ERROR: could not extend file "base/…": No space left on device
The disk holding the PostgreSQL data directory (or WAL) is full.
HTTP 508 Loop Detected (Resource Limit Is Reached)
Either the server detected an infinite loop (WebDAV) or — much more often — a cPanel/CloudLinux host is saying your account hit i…
HikariPool-1 - Connection is not available, request timed out after 30000ms
The connection pool was exhausted — all connections were busy for 30 seconds.
MongooseError: Operation `users.find()` buffering timed out after 10000ms
Mongoose queued a query waiting for a connection that never opened.
MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
The MongoDB driver couldn’t find a reachable server for the connection string.
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
A lazy-loaded association was accessed after the Hibernate session/transaction closed.
org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing
An entity references another entity that hasn’t been saved yet, and no cascade is configured.
org.hibernate.exception.ConstraintViolationException: could not execute statement
The database rejected an insert/update because of a constraint (unique, foreign key, not null).
Azure: SkuNotAvailable / QuotaExceeded when creating a VM or resource
The VM size isn’t offered in that region/zone for your subscription, or you’ve hit the vCPU quota.
HTTP 509 Bandwidth Limit Exceeded
A hosting-control-panel status (cPanel/Apache) meaning the account used up its monthly bandwidth allowance.
InsufficientInstanceCapacity: We currently do not have sufficient capacity in the Availability Zone you requested
AWS has no free capacity for that instance type in that Availability Zone right now.
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.
SSL error: tlsv1 alert protocol version / unsupported protocol / no protocols available
The client and server couldn’t agree on a TLS version or cipher, so the HTTPS handshake failed before any HTTP was exchanged.
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.
MySQL ERROR 1049 (42000): Unknown database 'x'
The database named in the connection doesn’t exist on that server.
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.
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.
Error: listen EADDRINUSE: address already in use :::3000
Another process is already listening on that port.
TypeError: Failed to fetch / NetworkError when attempting to fetch resource
The browser couldn’t complete the request at the network level — CORS, DNS, offline, blocked mixed content, or the server refused…
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.
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