Error map
SequelizeConnectionRefusedError SequelizeConnectionRefusedError: connect ECONNREFUSED 127.0.0.1:5432
Node.js · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (9). 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 (9)
PostgreSQL: could not connect to server / connection refused — Is the server running on host and accepting TCP/IP connections?
The client reached no PostgreSQL listener at that host/port — the server is down, listening elsewhere, or not accepting remote co…
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
A lazy-loaded association was accessed after the Hibernate session/transaction closed.
MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
The MongoDB driver couldn’t find a reachable server for the connection string.
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.
MongooseError: Operation `users.find()` buffering timed out after 10000ms
Mongoose queued a query waiting for a connection that never opened.
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.
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).
Two steps away (20)
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: database "x" does not exist
The connection names a database that isn’t on that server.
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class X and no properties discovered
Jackson can’t serialize the class — it has no public getters/fields, or it’s a Hibernate proxy, or Java 8 date types without the…
IncorrectResultSizeDataAccessException: query did not return a unique result: 2
A query expected one row but found several.
sqlalchemy.exc.IntegrityError: (psycopg2.errors.UniqueViolation) duplicate key value violates unique constraint
A database constraint (unique, foreign key, not null) rejected an insert/update made through SQLAlchemy.
CastError: Cast to ObjectId failed for value "x" (type string) at path "_id"
A value that isn’t a valid 24-hex-character ObjectId was used in an _id query.
MongoServerError: E11000 duplicate key error collection: db.users index: email_1 dup key
An insert/update violated a unique index in MongoDB.
ValidationError: User validation failed: email: Path `email` is required.
A document failed Mongoose schema validation before saving.
HikariPool-1 - Connection is not available, request timed out after 30000ms
The connection pool was exhausted — all connections were busy for 30 seconds.
PrismaClientKnownRequestError P2002: Unique constraint failed on the fields: (`email`)
A Prisma create/update violated a unique constraint.
Error: @prisma/client did not initialize yet. Please run "prisma generate"
The generated Prisma Client is missing or out of date.
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`.
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.
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.
MySQL ERROR 1062 (23000): Duplicate entry for key
An INSERT/UPDATE would create a duplicate value in a PRIMARY or UNIQUE key.
PostgreSQL: ERROR: duplicate key value violates unique constraint
An INSERT/UPDATE would create a duplicate in a UNIQUE or PRIMARY KEY column — or the id sequence is behind the existing data.
MySQL ERROR 1022 (23000): Can't write; duplicate key in table
An ALTER/CREATE produced a duplicate key or constraint name — often a foreign key name that already exists in the database.
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