Error map
Health checks failed ALB target unhealthy: Health checks failed with these codes: [404] / Request timed out
AWS · layer 6, Platform & cloud
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)
HTTP 503 Service Unavailable
The server is temporarily unable to handle the request — overloaded, in maintenance, or has no healthy backends.
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.
Elastic Beanstalk: Environment health has transitioned from Ok to Severe
Most instances in the Elastic Beanstalk environment are failing health checks or returning errors.
Liveness probe failed ... Container will be restarted (also Startup probe failed)
The kubelet’s liveness (or startup) check failed enough times that it killed and restarted the container.
HTTP 502 Bad Gateway
A proxy or gateway (Nginx, load balancer, CDN) got an invalid response — or no response — from the upstream server behind it.
Readiness probe failed: HTTP probe failed with statuscode: 503 / connect: connection refused
The container is running, but its readiness check fails, so the pod is marked not ready and removed from Service endpoints.
AccessDeniedException: User: arn:aws:iam::... is not authorized to perform: service:Action on resource: ...
The IAM user or role making the call has no permission for that action on that resource — the message names both.
Docker container is unhealthy (health check failing)
The container is running, but its HEALTHCHECK command keeps failing, so Docker (and dependent services) consider it unhealthy.
ECS: Essential container in task exited (task keeps stopping)
The main (essential) container stopped, so ECS stopped the whole task and the service keeps replacing it.
Two steps away (26)
Kubernetes: CrashLoopBackOff
The container starts, crashes (or exits), and Kubernetes keeps restarting it with increasing back-off delays.
HTTP 429 Too Many Requests
You’ve hit a rate limit — too many requests in a given time window. Slow down and retry later.
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
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.
Error: getaddrinfo ENOTFOUND host / Name or service not known
DNS lookup for the hostname failed — the name is wrong, doesn’t exist, or this machine can’t resolve it.
fatal: unable to access 'https://…': SSL certificate problem: unable to get local issuer certificate
Git doesn’t trust the HTTPS server’s certificate — corporate proxy, self-hosted Git with an internal CA, or outdated CA bundle.
Stack is in ROLLBACK_COMPLETE state and can not be updated
The stack’s first creation failed and rolled back; a stack in ROLLBACK_COMPLETE can only be deleted, not updated.
CloudFormation stack in UPDATE_ROLLBACK_FAILED
An update failed, and then the rollback also failed, leaving the stack stuck until you continue the rollback.
SES MessageRejected: Email address is not verified. The following identities failed the check in region
SES refused to send because the From address/domain isn’t verified — or the account is still in the SES sandbox, where recipients…
Kubernetes: OOMKilled (exit code 137)
The container used more memory than its limit, and the kernel killed it.
Error from server (BadRequest): container "x" in pod "y" is waiting to start: ContainerCreating
kubectl logs has nothing to show yet — the container hasn’t started (still creating, pulling, or blocked).
Error from server: admission webhook "validate.nginx.ingress.kubernetes.io" denied the request
A validating admission webhook (ingress-nginx, Gatekeeper/OPA, Kyverno) inspected your object and rejected it; the reason follows…
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.
HTTP 407 Proxy Authentication Required
A proxy between you and the server requires credentials before it will forward your request.
HTTP 504 Gateway Timeout
A proxy or gateway waited too long for the upstream server to respond and gave up.
Service has no endpoints (no endpoints available for service / Endpoints: <none>)
The Service’s selector matches no ready pods, so traffic to it is refused or returns 503.
deployment "x" exceeded its progress deadline (ProgressDeadlineExceeded)
A rollout didn’t make progress within progressDeadlineSeconds (default 600) — new pods never became ready.
AWS S3: AccessDenied (403) when calling GetObject / PutObject
An IAM policy, bucket policy, ACL/ownership setting, Block Public Access or KMS key policy denied the S3 request.
Azure: AuthorizationFailed — The client does not have authorization to perform action
The signed-in identity (user, service principal or managed identity) lacks an Azure RBAC role for that action on that scope.
PERMISSION_DENIED: The caller does not have permission (insufficient permissions)
You are authenticated, but your identity isn’t allowed to perform this action on this resource.
Conflict. The container name "/x" is already in use by container …
A container (running or stopped) already has that name; Docker won’t create a second one with the same name.
docker compose: services.x Additional property y is not allowed / yaml: line N: mapping values are not allowed
The compose file is invalid YAML or uses a key Compose doesn’t recognise at that level (usually an indentation mistake).
Docker container exits immediately (Exited (0) / Exited (1) right after start)
The container started and its main process finished at once, so the container stopped — Docker containers only live as long as PI…
npm ERR! code EROFS — EROFS: read-only file system
npm tried to write to a read-only location (read-only container filesystem, mounted volume, or system path).
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.
ECS: ResourceInitializationError: unable to pull secrets or registry auth
Fargate couldn’t fetch the task’s secrets (Secrets Manager/SSM) or registry credentials before starting containers.
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