Mistral AI Admission Controller Rejecting Requests During Multi-region Replication

Q: 3. Missing or Incorrect Region Labels

Workflows submitted from the us-west-2 cluster lacked the mandatory region label in their manifest. The admission controller therefore raised “missing region label on workflow manifest”. This aligns with the Banking service post‑deployment audit (2023‑09) where absent region tags caused systematic denials.

Q: 4. Policy Engine Conflict

A new compliance rule introduced for us-east-1 (data‑residency) was inadvertently applied globally because the policy scope was mis‑configured. Consequently, workflows from us-west-2 triggered PolicyViolationError despite being compliant for their own region. This mirrors GitHub issue #3890 where a region policy mismatch caused AdmissionDenied errors.

Q: Investigation and Debugging Steps Collect Admission Controller Logs

$ kubectl logs -n mistral $(kubectl get pods -n mistral -l app=admission-controller -o jsonpath="{.items[0].metadata.name}") -c controller 2024-07-12T14:03:21Z WARN AdmissionDenied: replication constraints violated (region: us-west-2, allowed: us-east-1) 2024-07-12T14:03:22Z ERROR PolicyViolationError: request exceeds regional compliance limits (policy: data-residency-us-east-1) Verify Replication Service Configuration $ kubectl get configmap mistral-replication-config -n mistral -o yaml apiVersion: v1 kind: ConfigMap metadata: name: mistral-replication-config data: allowedRegions: "us-east-1,eu-central-1" Inspect Workflow Manifest $ kubectl get mistralworkflow my-workflow -n prod -o yaml apiVersion: mistral.ai/v1 kind: Workflow metadata: name: my-workflow labels: # region label missing! spec: steps: [...] Check Policy Engine Scope $ curl -s https://policy-engine.internal/v1/policies?region=us-west-2 | jq . { "policyId": "data-residency-us-east-1", "scope": "global", #

Q: 2. Add Mandatory Region Label via Admission Patch

Introduce a mutating webhook that injects the region label based on the node’s AWS region metadata.

Q: 3. Restrict Policy Scope to Target Region

Modify the policy definition to limit its applicability to us-east-1 only.

Q: Verification Functional Test

$ kubectl apply -f test-workflow.yaml workflow.mistral.ai/test-workflow created Check the admission controller logs for a successful admission:

Problem: Admission Controller Rejects Workflow Execution During Multi‑Region Replication

In a Mistral AI deployment spanning multiple AWS regions, operators observed that workflow execution requests were being rejected by the admission controller. The errors manifested as:


AdmissionDenied: replication constraints violated (region: us-west-2, allowed: us-east-1)
PolicyViolationError: request exceeds regional compliance limits (policy: data-residency-us-east-1)
WorkflowRejected: admission controller timeout due to replication sync
ErrorCode 403 – Admission controller blocked request: region not authorized
AdmissionControllerError: missing region label on workflow manifest

The failures occurred immediately after enabling cross‑region workflow replication, causing a cascade of rejections that halted new workflow submissions across the fleet. The issue impacted high‑availability guarantees and compliance reporting for regulated workloads.

Root Cause Analysis

1. Admission Controller Checks

The Mistral AI admission controller performs three categories of checks before allowing a workflow to be persisted (Admission Controller Reference):

Replication Constraints: Ensures the workflow’s region label matches the set of regions that the replication service is currently configured to accept.
Region‑Specific Compliance Policies: Evaluates the workflow against policies defined in the Policy Engine (Region Policies), such as data residency or encryption mandates.
Manifest Completeness: Verifies required metadata (e.g., region label, replicationVersion) is present.

2. Misaligned Replication Configuration

During the multi‑region rollout, the replication service was updated to include us-east-1 and eu-central-1 as primary sources, but the admission controller’s internal whitelist still only contained us-east-1. This mismatch caused the controller to reject any workflow originating from us-west-2 with the error “replication constraints violated”. The situation mirrors the incident described in the FinTech platform outage (Q1 2024) where enabling AWS Global Accelerator exposed a similar whitelist discrepancy.

3. Missing or Incorrect Region Labels

Workflows submitted from the us-west-2 cluster lacked the mandatory region label in their manifest. The admission controller therefore raised “missing region label on workflow manifest”. This aligns with the Banking service post‑deployment audit (2023‑09) where absent region tags caused systematic denials.

4. Policy Engine Conflict

A new compliance rule introduced for us-east-1 (data‑residency) was inadvertently applied globally because the policy scope was mis‑configured. Consequently, workflows from us-west-2 triggered PolicyViolationError despite being compliant for their own region. This mirrors GitHub issue #3890 where a region policy mismatch caused AdmissionDenied errors.

Investigation and Debugging Steps

Collect Admission Controller Logs


$ kubectl logs -n mistral $(kubectl get pods -n mistral -l app=admission-controller -o jsonpath="{.items[0].metadata.name}") -c controller
2024-07-12T14:03:21Z WARN AdmissionDenied: replication constraints violated (region: us-west-2, allowed: us-east-1)
2024-07-12T14:03:22Z ERROR PolicyViolationError: request exceeds regional compliance limits (policy: data-residency-us-east-1)

Verify Replication Service Configuration


$ kubectl get configmap mistral-replication-config -n mistral -o yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: mistral-replication-config
data:
  allowedRegions: "us-east-1,eu-central-1"

Inspect Workflow Manifest


$ kubectl get mistralworkflow my-workflow -n prod -o yaml
apiVersion: mistral.ai/v1
kind: Workflow
metadata:
  name: my-workflow
  labels:
    # region label missing!
spec:
  steps: [...]

Check Policy Engine Scope


$ curl -s https://policy-engine.internal/v1/policies?region=us-west-2 | jq .
{
  "policyId": "data-residency-us-east-1",
  "scope": "global",   # <-- should be "us-east-1"
  "rules": [...]
}

Confirm Replication Lag


$ mistralctl replication status --region us-west-2
Region: us-west-2
Replication Lag: 45s
Last Sync: 2024-07-12T13:58:00Z

Resolution

1. Align Admission Controller Whitelist with Replication Service

Update the admission controller ConfigMap to include all active regions.

# Before
apiVersion: v1
kind: ConfigMap
metadata:
  name: admission-controller-config
  namespace: mistral
data:
  allowedRegions: "us-east-1"

# After
apiVersion: v1
kind: ConfigMap
metadata:
  name: admission-controller-config
  namespace: mistral
data:
  allowedRegions: "us-east-1,us-west-2,eu-central-1"

Apply and roll the config:


$ kubectl apply -f admission-controller-config.yaml
$ kubectl rollout restart deployment/mistral-admission-controller -n mistral

2. Add Mandatory Region Label via Admission Patch

Introduce a mutating webhook that injects the region label based on the node’s AWS region metadata.

# mutating-webhook.yaml (excerpt)
apiVersion: admissionregistration.k8s.io/v1
kind: MutatingWebhookConfiguration
metadata:
  name: mistral-workflow-mutation
webhooks:
- name: workflow.region.mistral.ai
  clientConfig:
    service:
      name: region-labeler
      namespace: mistral
      path: "/mutate"
  rules:
  - apiGroups: ["mistral.ai"]
    apiVersions: ["v1"]
    operations: ["CREATE"]
    resources: ["workflows"]

3. Restrict Policy Scope to Target Region

Modify the policy definition to limit its applicability to us-east-1 only.

# Before (global scope)
{
  "policyId": "data-residency-us-east-1",
  "scope": "global",
  "rules": [...]
}

# After (region‑scoped)
{
  "policyId": "data-residency-us-east-1",
  "scope": "us-east-1",
  "rules": [...]
}

Reload policies:


$ curl -X POST https://policy-engine.internal/v1/policies/reload

4. Tune Replication Sync Timeout

Increase the admission controller’s replication‑sync timeout from 30s to 60s to accommodate transient lag during peak traffic, as recommended in the Multi‑Region Deployment Guide.

# admission-controller-config.yaml (excerpt)
data:
  replicationSyncTimeout: "60s"

Verification

Functional Test


$ kubectl apply -f test-workflow.yaml
workflow.mistral.ai/test-workflow created

Check the admission controller logs for a successful admission:


2024-07-12T14:15:03Z INFO AdmissionAccepted: workflow test-workflow (region: us-west-2)

Cross‑Region Replication Confirmation


$ mistralctl workflow get test-workflow --region eu-central-1
Status: READY
ReplicationState: SYNCHRONIZED

Policy Enforcement Validation

Submit a workflow that intentionally violates the us-east-1 data‑residency rule from us-west-2. The admission should succeed because the policy no longer applies globally.


$ kubectl apply -f violating-workflow.yaml
workflow.mistral.ai/violating-workflow created

Prevention and Best Practices

Centralize Region Whitelists: Store allowed regions in a single ConfigMap referenced by both the replication service and admission controller to avoid drift.
Automate Region Label Injection: Deploy the mutating webhook in every cluster to guarantee the region label is never missing.
Scope Policies Explicitly: Always define scope in policy JSON; avoid defaulting to global unless truly intended.
Monitor Replication Lag: Set an alert on mistral_replication_lag_seconds exceeding 30 s; tie the alert to a runbook that checks admission controller timeouts.
Versioned Configuration: Use GitOps (e.g., ArgoCD) to version‑control admission controller and replication configs, enabling rollback if a region is inadvertently removed.
Periodic Compliance Audits: Run a nightly script that validates all policies have a region‑specific scope and that every workflow manifest includes a region label.

Related Topic Hub: LLM Systems Troubleshooting Hub

FAQ

Why does the admission controller reject requests only from certain regions?
The controller checks the allowedRegions list. If a region is not present, the request is denied with “replication constraints violated”. Ensure the list matches the replication topology.
Can I temporarily bypass region policies for testing?
Yes. Add a temporary policyOverride annotation to the workflow manifest (e.g., mistral.ai/override-policy: true) and configure the admission controller to honor it. Remove the annotation after testing.
What causes “AdmissionControllerError: missing region label on workflow manifest”?
The workflow YAML lacks a metadata.labels.region entry. Deploy the mutating webhook that injects this label based on the node’s AWS metadata, or add the label manually.
How do I differentiate between a replication lag timeout and a policy violation?
Replication timeouts surface as “WorkflowRejected: admission controller timeout due to replication sync”. Policy violations appear as “PolicyViolationError” with the specific policy ID. Check the log prefix and the error code (403 vs 504).
Is there a way to query which policies were evaluated for a rejected request?
Enable verbose admission logging (logLevel: DEBUG) in the admission controller ConfigMap. The logs will list each policy ID evaluated and the decision outcome.