Error map
MongoNetworkError: connect ECONNREFUSED 127.0.0.1:27017 MongoDB: MongoServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
MongoDB · layer 5, Data
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)
MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
The MongoDB driver couldn’t find a reachable server for the connection string.
MongoDB: MongoParseError: Invalid scheme, expected connection string to start with "mongodb://" or "mongodb+srv://"
The connection string is missing, malformed, or the environment variable holding it is undefined.
MongoDB: MongoServerError: bad auth : Authentication failed (code 8000 / 18)
MongoDB (often Atlas) rejected the username/password in the connection string.
MongoDB Atlas: Error: querySrv ENOTFOUND _mongodb._tcp.cluster0.abcde.mongodb.net
The driver couldn't resolve the `mongodb+srv://` SRV record for your cluster.
mongod: Process exited with status 14 — Exception in initAndListen: IllegalOperation: Attempted to create a lock file on a read-only directory
`mongod` couldn't start because the data directory or log/socket file isn't writable or already locked.
MongoDB: connection refused / timed out from a remote host — mongod bindIp defaults to 127.0.0.1
MongoDB only listens on localhost by default, so remote clients can't connect.
MongoServerError: bad auth : Authentication failed. (Atlas user / special characters in password)
Atlas rejected the username/password in the connection string.
MongoServerError: Exceeded memory limit for $group, but didn't allow external sort. Pass allowDiskUse:true to opt in
An aggregation stage needed more than 100 MB of RAM and spilling to disk wasn't enabled.
MongoServerError: BSONObj size: 17825792 (0x1100000) is invalid. Size must be between 0 and 16793600(16MB)
A single document (or an aggregation result row) grew past MongoDB's 16 MB limit.
MongoServerSelectionError: Server selection timed out after 30000 ms — topology type ReplicaSetNoPrimary
The driver sees the replica set members but none is a primary (election failing or members unreachable).
MongoDB: bash: mongo: command not found / zsh: command not found: mongo
The legacy `mongo` shell was removed from MongoDB 6.0+ installs; the shell is now `mongosh`, or MongoDB isn't installed.
PyMongo: pymongo.errors.ServerSelectionTimeoutError: localhost:27017: [Errno 111] Connection refused, Timeout: 30s
PyMongo couldn't find a usable MongoDB server within the selection timeout.
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.
MongooseError: Operation `users.find()` buffering timed out after 10000ms
Mongoose queued a query waiting for a connection that never opened.
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.
HTTP 413 Content Too Large (Request Entity Too Large)
The request body is bigger than the server is willing to accept — usually a file upload over the configured limit.
OAuth Error: redirect_uri_mismatch
The redirect URI in your OAuth request doesn’t exactly match one registered for the client in the provider’s console.
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.
Git: Permission denied (publickey). fatal: Could not read from remote repository.
SSH authentication to GitHub/GitLab/Bitbucket failed — no key, wrong key, or the key isn’t added to your account.
Azure AD (Entra ID): AADSTS700016 Application not found in the directory
The client ID in your sign-in request doesn’t exist in the tenant you’re authenticating against.
HTTP 401 Unauthorized
The request has no valid authentication credentials — you need to log in or send a valid token.
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.
dial tcp: lookup registry-1.docker.io: no such host / Temporary failure in name resolution during docker build
DNS isn’t working for the Docker daemon or inside build containers, so pulls and package downloads fail.
DNS not working inside a Kubernetes pod (could not resolve host / nslookup: can't resolve)
Pods can’t resolve service names or external hosts — CoreDNS is down, blocked by NetworkPolicy, or the upstream resolver fails.
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
The docker CLI can’t talk to the Docker engine — it isn’t running, or your user can’t access the socket.
user is not in the sudoers file. This incident will be reported.
Your account isn’t allowed to use sudo.
Error: listen EACCES: permission denied 0.0.0.0:80
Node isn’t allowed to bind that port — ports below 1024 need root on Linux/macOS, and some Windows ports are reserved.
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.
Error response from daemon: network X not found
The container or Compose project refers to a Docker network that doesn’t exist (any more).
Error response from daemon: Pool overlaps with other one on this address space
Docker tried to create a network whose subnet clashes with an existing Docker network (or a VPN/host route).
MongoServerError: E11000 duplicate key error collection: db.users index: email_1 dup key
An insert/update violated a unique index in MongoDB.
ReplyError: NOAUTH Authentication required.
The Redis server requires a password (or ACL user) but the client didn’t authenticate.
denied: Your authorization token has expired. Reauthenticate and try again. (Amazon ECR)
Docker’s login to Amazon ECR has expired — ECR tokens last 12 hours, so pushes and pulls fail until you log in again.
Kubernetes: OOMKilled (exit code 137)
The container used more memory than its limit, and the kernel killed it.
Segmentation fault (core dumped)
A program accessed memory it wasn’t allowed to, and the kernel killed it with SIGSEGV (exit code 139).
Killed / Out of memory: Killed process (Linux OOM killer)
The kernel ran out of memory and killed a process to recover — the program just prints “Killed” (exit code 137).
Too many open files (EMFILE)
The process hit its file-descriptor limit — sockets, files and pipes all count.
ValidationError: User validation failed: email: Path `email` is required.
A document failed Mongoose schema validation before saving.
Lambda: Request must be smaller than 6291456 bytes for the InvokeFunction operation (RequestEntityTooLargeException)
The event payload (or response) is over Lambda’s 6 MB synchronous limit (256 KB for async invocations).
MongoServerError: Transaction numbers are only allowed on a replica set member or mongos
You started a transaction (or used retryWrites) on a standalone MongoDB server, which doesn't support them.
MongoServerError: not primary and secondaryOk=false / NotWritablePrimary: not master
A write (or read without secondary preference) hit a secondary — the primary changed or you connected directly to a secondary.
MongoServerError: cursor id 1234567890 not found (CursorNotFound)
A cursor you were iterating timed out or was killed on the server, so the next batch fails.
bash: command not found
The shell can’t find an executable with that name in any directory on your PATH.
[nodemon] app crashed - waiting for file changes before starting...
Your app threw an error on startup; nodemon is waiting for a file change to retry.
macOS: zsh: command not found: brew (Homebrew not on PATH on Apple Silicon)
Homebrew is installed in /opt/homebrew on Apple Silicon Macs, which isn’t on PATH until you add its shellenv line.
MongoServerSelectionError: Could not connect to any servers in your MongoDB Atlas cluster. One common reason is that you're trying to access the database from an IP that isn't whitelisted
Atlas rejects connections from IP addresses that aren't in the project's Network Access list.
PyMongo: pymongo.errors.BulkWriteError: batch op errors occurred
A bulk insert/update had one or more failed operations; details are in `e.details`.
PyMongo: NotImplementedError: Database objects do not implement truth value testing or bool(). Please compare with None instead: database is not None
You used a Database/Collection object in an `if` (`if db:`), which PyMongo forbids.
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