Engineer-written guides
Fix Software Errors, Fast.
Practical troubleshooting guides for 9290+ real-world errors in OpenAI, Docker, Kubernetes, AWS, Python, Linux and more.
AWS 5 articles
- AWS AccessDeniedException: User is not authorized IAM user or role lacks the required permission for the requested action CLI / SDK
- AWS InvalidClientTokenId: The security token is invalid AWS credentials are malformed, expired, or for the wrong region CLI / SDK
- AWS ThrottlingException: Rate exceeded AWS API calls exceeded the allowed request rate for the account SDK / API
- AWS S3 403 Forbidden – Access Denied S3 bucket policy or ACL blocks the requested operation S3 / CLI
- AWS EKS You must be logged in to the server (Unauthorized) kubectl cannot authenticate to the EKS cluster EKS / CLI
Django 13 articles
- django.db.utils.IntegrityError: duplicate key value violates unique constraint This database error indicates an attempt to insert or update data that would violate a unique constraint (e.g., adding a record with a non-unique ID or email). runtime, database, ORM
- django.db.utils.OperationalError: could not connect to server: Connection refused This database error means the Django application failed to connect to the database server, often due to the server not running or incorrect connection details. runtime, database, setup
- django.core.exceptions.ObjectDoesNotExist: X matching query does not exist. This error is raised by Django's ORM when a `get()` query returns no object. runtime, ORM
- django.core.exceptions.MultipleObjectsReturned: get() returned more than one X This error occurs when a Django `get()` query returns multiple objects, but `get()` expects only one. runtime, ORM
- django.db.utils.DataError: value too long for type character varying(X) This database error indicates an attempt to save a string value that exceeds the maximum length defined for a database column. runtime, database, ORM
- django.db.utils.ProgrammingError: column "X" does not exist This database error usually means a database query refers to a column that does not exist, often due to missing or outdated migrations. runtime, database, ORM, migrations
- django.db.utils.InterfaceError: connection already closed This database error indicates an attempt to use a database connection that has already been closed or lost. runtime, database
- django.db.migrations.exceptions.InconsistentMigrationHistory This error occurs when the database's migration history doesn't match the migration files, often due to manual database changes or concurrent deploys. build, CLI, migrations
- django.db.utils.InternalError: current transaction is aborted, commands ignored until end of transaction block This error means a database transaction failed, often due to a previous error within the transaction, and subsequent commands are being ignored. runtime, database, ORM
- django.urls.exceptions.NoReverseMatch: Reverse for 'X' not found. 'X' is not a valid view function or pattern name. This error happens when Django cannot find a URL pattern matching the name provided to `reverse()` or in template tags like `{% url %}`. runtime, URLs, templates
- django.template.exceptions.TemplateSyntaxError: Invalid block tag on line X This error indicates an incorrect or unrecognized Django template tag used in a template file. runtime, templates
- django.template.exceptions.TemplateDoesNotExist: 'X.html' This error means Django could not find a template file at the specified path, or in any configured template directories. runtime, templates
- django.http.Http404 This is Django's specific exception for a 'Not Found' error, typically raised in views when an object or resource does not exist. runtime, API, web
Docker 5 articles
- Docker container exited with code 1 Container process terminated with a general error CLI / runtime
- Docker OOMKilled – container killed due to out of memory The container exceeded its memory limit and was killed by the kernel runtime
- Docker permission denied while connecting to daemon socket Current user is not in the docker group or daemon is not running CLI
- Docker pull – image not found (manifest unknown) The specified Docker image or tag does not exist in the registry CLI
- Docker Error: port is already allocated The host port is already in use by another process or container CLI
Gemini 4 articles
- ResourceExhausted: 429 Quota Exceeded Google Gemini API free-tier quota exhausted API
- PermissionDenied: 403 Forbidden API key lacks permission or the model is restricted in your region API
- Unauthenticated: 401 API key invalid The provided Gemini API key is missing or malformed API
- BlockedBySafetySettings The response was blocked by Gemini content safety filters API
Git 4 articles
- Git merge conflict – Automatic merge failed; fix conflicts Two branches have incompatible changes to the same lines CLI
- Git error: failed to push some refs – remote contains work you do not have The remote branch has commits not in your local branch CLI
- Git warning: You are in 'detached HEAD' state HEAD points directly to a commit instead of a branch CLI
- Git error: Permission denied (publickey) SSH key is missing, not added to agent, or not registered on the remote CLI / SSH
GitHub Actions 3 articles
- GitHub Actions Error: secret not found or empty A workflow references a secret that is not defined in repo settings CI/CD
- GitHub Actions Error: Resource not accessible by integration The GITHUB_TOKEN lacks required permissions for the action CI/CD
- GitHub Actions Error: The job running has exceeded the maximum execution time The workflow job exceeded the 6-hour (or custom) timeout limit CI/CD
HTTP 3 articles
- CORS Error: Access-Control-Allow-Origin missing or blocked The browser blocked a cross-origin request due to missing CORS headers browser / API
- HTTP 401 Unauthorized The request lacks valid authentication credentials API
- HTTP 403 Forbidden The server understood the request but refuses to authorise it API
Kubernetes 5 articles
- Kubernetes CrashLoopBackOff Pod keeps crashing and Kubernetes is backing off restart attempts cluster
- Kubernetes ImagePullBackOff Kubernetes cannot pull the container image from the registry cluster
- Kubernetes OOMKilled – pod terminated due to memory limit The container exceeded its memory limit and was killed by Kubernetes cluster
- Kubernetes pod stuck in Pending state Pod cannot be scheduled due to resource constraints or node issues cluster
- Kubernetes kubectl connection refused to API server kubectl cannot reach the Kubernetes API server CLI
Linux 5 articles
- Linux bash: Permission denied The current user lacks execute or read permission on the file shell / CLI
- Linux bash: No such file or directory The specified file or directory path does not exist shell / CLI
- Linux bind: Address already in use (EADDRINUSE) A process is already listening on the requested port networking / runtime
- Linux No space left on device (ENOSPC) The disk partition has no remaining free space filesystem
- Linux process Killed (signal 9 / SIGKILL) The OOM killer or a user terminated the process forcefully process management
MongoDB 2 articles
MySQL 3 articles
- MySQL ERROR 1045: Access denied for user Wrong username, password, or host not allowed in MySQL user grants database
- MySQL ERROR 1049: Unknown database 'X' The specified database does not exist on this MySQL server database
- MySQL ERROR 2003: Can't connect to MySQL server on 'host' MySQL server is not running or the host/port is incorrect database
Next.js 2 articles
Nginx 3 articles
- Nginx 502 Bad Gateway Nginx received an invalid response from the upstream server reverse proxy
- Nginx 504 Gateway Timeout The upstream server did not respond in time reverse proxy
- Nginx error: permission denied while connecting to upstream SELinux or filesystem permissions block Nginx from reaching the socket server / Linux
Node.js 4 articles
- Node.js Error: ENOENT no such file or directory Node cannot find the file or directory specified in the operation runtime
- Node.js Error: EADDRINUSE port already in use The port your app is trying to bind to is already occupied runtime / networking
- Node.js Error: Cannot find module 'X' The required Node module is missing from node_modules runtime
- Node.js FATAL ERROR: Reached heap limit – JavaScript heap out of memory The Node.js process exceeded its default V8 heap size limit runtime
OpenAI 6 articles
- RateLimitError: 429 Too Many Requests OpenAI API rate limit exceeded for your current plan tier API
- AuthenticationError: 401 Unauthorized Invalid or missing OpenAI API key API
- ServiceUnavailableError: 503 Service Unavailable OpenAI API is temporarily overloaded or down API
- InternalServerError: 500 Internal Server Error An unexpected error occurred on OpenAI's server side API
- InvalidRequestError: context_length_exceeded The prompt exceeds the maximum token limit for the model API
- BadRequestError: 400 Bad Request Malformed request body or invalid parameters sent to the API API
PostgreSQL 3 articles
- PostgreSQL: connection refused – could not connect to server PostgreSQL is not running, wrong port, or firewall is blocking the connection database
- PostgreSQL error: password authentication failed for user Wrong password or pg_hba.conf rejects the authentication method database
- PostgreSQL FATAL: remaining connection slots are reserved The database has hit its max_connections limit database
Python 32 articles
- Python ModuleNotFoundError: No module named 'X' The imported module is not installed in the active Python environment runtime
- Python ImportError: cannot import name 'X' from 'Y' The specific name being imported does not exist in the target module runtime
- Python AttributeError: object has no attribute 'X' Trying to access a method or property that doesn't exist on an object runtime
- Python TypeError: unsupported operand type(s) An operation is applied to objects of incompatible types runtime
- Python RecursionError: maximum recursion depth exceeded A function calls itself too many times without a proper base case runtime
- SyntaxError: invalid syntax This error occurs when the Python interpreter finds a grammatical mistake in the code. runtime, build, CLI
- IndentationError: expected an indented block This error signifies incorrect indentation, which is crucial for Python's block structure. runtime, build, CLI
- NameError: name 'X' is not defined This error indicates that a variable or function name was used before it was assigned or defined. runtime
- ValueError: invalid literal for int() with base 10: 'X' This error occurs when a function receives an argument of the correct type but an inappropriate value, such as trying to convert a non-numeric string to an integer. runtime
- IndexError: list index out of range This error means you are trying to access an index of a sequence (like a list or tuple) that does not exist. runtime
- KeyError: 'X' This error occurs when you try to access a dictionary key that does not exist. runtime
- ZeroDivisionError: division by zero This error happens when an attempt is made to divide a number by zero. runtime
- FileNotFoundError: [Errno 2] No such file or directory: 'X' This error indicates that a file or directory being accessed does not exist at the specified path. runtime, filesystem
- OSError: [Errno 13] Permission denied: 'X' This error means the operating system denied access to a file or resource, often due to insufficient permissions. runtime, filesystem, CLI
- StopIteration This error signals that an iterator has no more items to produce. runtime
- MemoryError This error occurs when an operation runs out of available memory. runtime
- KeyboardInterrupt This error is raised when the user interrupts program execution, typically by pressing Ctrl+C. runtime, CLI
- UnboundLocalError: local variable 'X' referenced before assignment This error occurs when a local variable is accessed within a function before it has been assigned a value. runtime
- AssertionError This error is raised when an assert statement fails, indicating an unexpected condition in the code. runtime, testing
- RuntimeError: dictionary changed size during iteration This error occurs when a dictionary is modified (items added or removed) while it is being iterated over. runtime
- IOError: [Errno 22] Invalid argument This error signifies that an I/O operation received an argument that is invalid or inappropriate for the operation. runtime, filesystem
- TypeError: 'NoneType' object is not subscriptable This error means you are trying to access an item from an object that is None, as if it were a sequence or mapping. runtime
- TypeError: object is not callable This error occurs when you try to call something that is not a function or method, like a variable assigned to a non-callable object. runtime
- BrokenPipeError: [Errno 32] Broken pipe This error indicates that one end of a pipe (e.g., a connection to another process) has been closed while the other end is still trying to write to it. runtime, inter-process communication
- SystemExit: 1 This error is raised by the sys.exit() function and indicates that the program is exiting, often with an error status. runtime, CLI
- AttributeError: module 'X' has no attribute 'Y' This error means you are trying to access a non-existent attribute or member of a Python module. runtime
- ValueError: not enough values to unpack (expected 2, got 1) This error happens during sequence unpacking when the number of items on the right side does not match the number of variables on the left side. runtime
- TypeError: can only concatenate str (not "int") to str This error indicates an attempt to combine a string with an integer using an operator like `+` without explicit type conversion. runtime
- ValueError: substring not found This error is raised by string methods like `str.index()` when the specified substring is not present in the string. runtime
- UnicodeDecodeError: 'utf-8' codec can't decode byte 0x... in position X: invalid start byte This error occurs when the Python interpreter tries to decode a byte sequence using 'utf-8' but encounters bytes that are not valid in that encoding. runtime, file I/O, network
- json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0) This error means that the JSON parser encountered invalid JSON syntax, often when the input is empty or malformed. runtime, API, data parsing
- socket.timeout: The read operation timed out This error indicates that a network socket operation, such as reading data, did not complete within the specified timeout period. runtime, network, API
React 2 articles
- React Hydration Error: server HTML does not match client render The server-rendered HTML differs from what React renders on the client runtime / SSR
- React Error: Invalid hook call – Hooks can only be called inside a function component A React hook is called outside of a component or inside a class component runtime
Redis 2 articles
SSL/TLS 3 articles
- SSL certificate has expired The TLS certificate's notAfter date is in the past HTTPS / networking
- SSL certificate error: self-signed certificate in certificate chain The certificate is not issued by a trusted CA HTTPS / networking
- SSL handshake failure: TLSv1 Alert Client and server cannot agree on a TLS version or cipher suite HTTPS / networking
Terraform 2 articles
TypeScript 3 articles
- TypeScript TS2345: Argument of type 'X' is not assignable to parameter of type 'Y' A value of the wrong type is passed to a function parameter compile
- TypeScript TS2339: Property 'X' does not exist on type 'Y' Accessing a property that is not defined in the type declaration compile
- TypeScript TS2307: Cannot find module 'X' or its corresponding type declarations The module is missing or has no @types package installed compile
npm 3 articles
- npm ERR! ERESOLVE unable to resolve dependency tree npm cannot find a compatible version for a dependency CLI
- npm ERR! EACCES permission denied npm lacks write permission to the global node_modules directory CLI
- npm ERR! 404 Not Found – package not found in registry The package name does not exist in the npm registry CLI
requests 2 articles
- requests.exceptions.ConnectionError: HTTPSConnectionPool This error signifies that the 'requests' library failed to establish a connection to the specified URL, often due to network issues or DNS problems. runtime, network, API
- requests.exceptions.Timeout: HTTPSConnectionPool This error means that the 'requests' library exceeded the configured timeout while waiting for a response from the server. runtime, network, API