Error map
ActionController::ParameterMissing: param is missing or the value is empty Rails: ActionController::ParameterMissing: param is missing or the value is empty: user
Ruby / Rails · 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)
Rails: ActiveRecord::IrreversibleMigration — This migration uses remove_column without a type; db:rollback can't reverse it
`rails db:rollback` can't undo the migration because it contains an operation Rails can't invert.
Ruby: ArgumentError: missing keyword: :name / unknown keyword: :nmae
A method requiring keyword arguments was called without them, or with a misspelt keyword.
Rails: ActiveRecord::ConnectionNotEstablished: No connection pool for 'ActiveRecord::Base' found
ActiveRecord has no database connection configured or established for this process.
Rails: ActiveRecord::Deadlocked: PG::TRDeadlockDetected: ERROR: deadlock detected
Two transactions locked rows in opposite orders, so PostgreSQL aborted one.
Rails: ActiveModel::ForbiddenAttributesError
You passed raw `params` to `new/create/update`, but strong parameters require permitting attributes first.
Rails: ActiveRecord::RecordInvalid: Validation failed: Email can't be blank, Name is too short
`save!`/`create!`/`update!` raised because validations failed.
Rails: ActionController::UnknownFormat — UsersController#show is missing a template for this request format and variant
The controller has no template or `respond_to` handler for the requested format (HTML/JSON/etc.).
Rails: AbstractController::DoubleRenderError (Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action)
An action called `render`/`redirect_to` more than once.
Rails: ActiveRecord::AssociationTypeMismatch: User(#1234) expected, got "42" which is an instance of String(#5678)
You assigned the wrong kind of object (or an id string) to an association.
Two steps away (22)
MySQL ERROR 1146 (42S02): Table 'db.table' doesn't exist
The query references a table that MySQL can’t find in that database.
PostgreSQL: ERROR: relation "x" does not exist
The table/view isn’t found — missing migration, wrong schema, or a case-sensitive quoted name.
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.
Ruby: NoMethodError: undefined method `x' for nil (nil:NilClass)
You called a method on nil — the object you expected (a record, hash value, param) wasn’t there.
macOS: ERROR: While executing gem ... (Gem::FilePermissionError) You don't have write permissions for the /Library/Ruby/Gems/2.6.0 directory
`gem install` tries to write into Apple's system Ruby, which is protected and shouldn't be modified.
Ruby: NameError: undefined local variable or method 'x' for main:Object
Ruby saw a bare identifier that is neither a local variable nor a method on the current object.
Rails: ActionController::InvalidAuthenticityToken (Can't verify CSRF token authenticity)
A non-GET request arrived without a valid CSRF token for the session.
Redis: Error: connect ECONNREFUSED 127.0.0.1:6379 / Could not connect to Redis at 127.0.0.1:6379: Connection refused
Nothing is listening on the Redis host/port your client uses.
Redis: Error: write EPROTO ... SSL routines:ssl3_get_record:wrong version number / Connection reset by peer (TLS vs plaintext)
The client and server disagree about TLS — plaintext client to a TLS port, or TLS client to a plaintext port.
Ruby: NameError: uninitialized constant UsersController::User (Did you mean? Users)
Ruby (or Rails autoloading) couldn't find a class or module with that name in the current scope.
Rails: ActiveRecord::RecordNotFound: Couldn't find User with 'id'=42
`find`/`find_by!` didn't find a row, so Rails raises (and renders a 404 in production).
Rails: ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR: relation "users" does not exist
Rails queried a table that isn't in the connected PostgreSQL database.
WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! (ssh host key changed)
The server’s SSH host key differs from the one saved in ~/.ssh/known_hosts — usually because the server was rebuilt or the IP was…
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY
apt can’t verify a repository’s signature because the repo’s signing key isn’t installed (or has expired/rotated).
SELinux is preventing ... / avc: denied { read } for pid=... (permission denied despite correct permissions)
SELinux blocked the access — file permissions look fine, but the file’s security context or a boolean doesn’t allow the service t…
Rails: ActiveRecord::RecordNotUnique: PG::UniqueViolation: ERROR: duplicate key value violates unique constraint "index_users_on_email"
A unique index rejected an insert/update because the value already exists.
Rails: PG::ConnectionBad: could not connect to server: Connection refused. Is the server running on host "localhost" (127.0.0.1) and accepting TCP/IP connections on port 5432?
Rails can't reach PostgreSQL — the server is down, wrong host/port/socket, or credentials/pg_hba block it.
Rails: ActiveRecord::ReadOnlyRecord: Order is marked as readonly
You tried to save a record that was loaded as read-only (e.g. via `joins` in old Rails or `readonly` scope).
Rails: ActionView::MissingTemplate (Missing template users/show, application/show with {:locale=>[:en], :formats=>[:html], :handlers=>[:erb, :builder, :raw, :ruby, :jbuilder]})
The action tried to render a view that doesn't exist for the requested format/handler.
Rails: ActiveRecord::PendingMigrationError — Migrations are pending. To resolve this issue, run: bin/rails db:migrate
The database schema is behind the migration files in the app.
Rails: ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'users.nickname' in 'field list'
The query references a column that doesn't exist in the table (missing migration, typo or stale schema cache).
Rails: ActiveRecord::StatementInvalid: PG::DuplicateColumn: ERROR: column "status" of relation "orders" already exists
A migration tried to add a column/table/index that already exists.
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