managing-linkerd

name	managing-linkerd
description	Use when working with Linkerd — linkerd service mesh management for Kubernetes. Covers proxy injection, traffic splitting, service profiles, tap/top monitoring, mTLS verification, health checks, and dashboard access. Use when managing Linkerd mesh, debugging service communication, configuring traffic splits, or monitoring mesh health.
connection_type	linkerd
preload	false

Linkerd Service Mesh Skill

Manage Linkerd service mesh, traffic splitting, service profiles, and observability.

Core Helper Functions

#!/bin/bash

# Linkerd CLI wrapper
linkerd_cmd() {
    linkerd "$@" 2>/dev/null
}

# Get Linkerd CRDs via kubectl
linkerd_get() {
    local resource="$1"
    local ns="${2:---all-namespaces}"
    if [ "$ns" = "--all-namespaces" ]; then
        kubectl get "$resource" -A -o json 2>/dev/null
    else
        kubectl get "$resource" -n "$ns" -o json 2>/dev/null
    fi
}

MANDATORY: Discovery-First Pattern

Always check mesh health and injection status before performing operations.

Phase 1: Discovery

#!/bin/bash

echo "=== Linkerd Version ==="
linkerd version 2>/dev/null

echo ""
echo "=== Control Plane Health ==="
linkerd check --pre 2>/dev/null | tail -20

echo ""
echo "=== Control Plane Pods ==="
kubectl get pods -n linkerd -o json 2>/dev/null | jq -r '
    .items[] | "\(.metadata.name)\t\(.status.phase)\t\(.status.containerStatuses[0].restartCount // 0) restarts"
' | column -t

echo ""
echo "=== Meshed Namespaces ==="
kubectl get namespaces -o json 2>/dev/null | jq -r '
    .items[] | select(.metadata.annotations["linkerd.io/inject"] == "enabled") | .metadata.name
'

echo ""
echo "=== Meshed Deployments ==="
linkerd stat deployments -A 2>/dev/null | head -25

Output Rules

• TOKEN EFFICIENCY: Target <=50 lines per output
• Use linkerd stat for quick metrics summaries
• Use -o json with jq for Linkerd CRDs via kubectl

Common Operations

Mesh Traffic Dashboard

#!/bin/bash
NS="${1:-default}"

echo "=== Deployment Stats: $NS ==="
linkerd stat deploy -n "$NS" 2>/dev/null | head -20

echo ""
echo "=== Top Routes (live traffic) ==="
linkerd top deploy -n "$NS" --hide-sources 2>/dev/null | head -15

echo ""
echo "=== Request Success Rates ==="
linkerd stat deploy -n "$NS" -o json 2>/dev/null | jq -r '
    .[] | "\(.resource)\t\(.successRate)\t\(.rps)\t\(.latencyP50)ms p50\t\(.latencyP99)ms p99"
' | column -t | head -20

Service Profiles & Routes

#!/bin/bash
NS="${1:-default}"

echo "=== Service Profiles ==="
kubectl get serviceprofiles -n "$NS" -o json 2>/dev/null | jq -r '
    .items[] | "\(.metadata.name)\t\(.spec.routes | length) routes"
' | column -t

echo ""
echo "=== Route Metrics ==="
for sp in $(kubectl get serviceprofiles -n "$NS" -o jsonpath='{.items[*].metadata.name}' 2>/dev/null); do
    SVC=$(echo "$sp" | sed 's/\..*$//')
    echo "--- $SVC ---"
    linkerd routes deploy/"$SVC" -n "$NS" 2>/dev/null | head -10
done

echo ""
echo "=== Retry & Timeout Config ==="
kubectl get serviceprofiles -n "$NS" -o json 2>/dev/null | jq '
    .items[] | {
        name: .metadata.name,
        routes: [.spec.routes[] | {
            name: .name,
            timeout: .timeout,
            is_retryable: .isRetryable
        }]
    }' | head -30

Traffic Split Management

#!/bin/bash
NS="${1:-default}"

echo "=== Active Traffic Splits ==="
kubectl get trafficsplits -n "$NS" -o json 2>/dev/null | jq -r '
    .items[] | {
        name: .metadata.name,
        service: .spec.service,
        backends: [.spec.backends[] | "\(.service): \(.weight)"]
    }'

echo ""
echo "=== Backend Health ==="
kubectl get trafficsplits -n "$NS" -o json 2>/dev/null | jq -r '.items[].spec.backends[].service' \
    | while read svc; do
        echo "--- $svc ---"
        linkerd stat deploy/"$svc" -n "$NS" 2>/dev/null | tail -1
    done

mTLS Verification

#!/bin/bash
NS="${1:-default}"

echo "=== mTLS Status ==="
linkerd edges deploy -n "$NS" 2>/dev/null | head -20

echo ""
echo "=== Identity Certificates ==="
linkerd identity -n "$NS" 2>/dev/null | head -15

echo ""
echo "=== Tap: Live mTLS Connections ==="
linkerd tap deploy -n "$NS" --max-rps 5 2>/dev/null | head -10

echo ""
echo "=== Certificate Expiry ==="
kubectl get secret -n linkerd -o json 2>/dev/null | jq -r '
    .items[] | select(.metadata.name | test("issuer|ca")) |
    "\(.metadata.name)\t\(.type)"
' | column -t

Health Check & Diagnostics

#!/bin/bash
echo "=== Full Health Check ==="
linkerd check 2>/dev/null | grep -E "^[√×‼]|Status" | head -30

echo ""
echo "=== Proxy Diagnostics ==="
POD="${1:-}"
NS="${2:-default}"
if [ -n "$POD" ]; then
    echo "--- Proxy for $POD ---"
    linkerd diagnostics proxy-metrics "$POD" -n "$NS" 2>/dev/null | head -20
    echo ""
    kubectl logs "$POD" -n "$NS" -c linkerd-proxy --tail 20 2>/dev/null
fi

echo ""
echo "=== Data Plane Integrity ==="
linkerd check --proxy -n "${NS:-default}" 2>/dev/null | grep -E "^[√×‼]" | head -15

Safety Rules

• Read-only by default: Use linkerd stat, linkerd check, linkerd edges for inspection
• Never modify TrafficSplits without explicit user confirmation -- affects live traffic
• Tap is intrusive: linkerd tap captures live traffic -- use sparingly and with --max-rps
• Injection changes: Enabling/disabling injection requires pod restart to take effect

Output Format

Present results as a structured report:

Managing Linkerd Report
═══════════════════════
Resources discovered: [count]

Resource       Status    Key Metric    Issues
──────────────────────────────────────────────
[name]         [ok/warn] [value]       [findings]

Summary: [total] resources | [ok] healthy | [warn] warnings | [crit] critical
Action Items: [list of prioritized findings]

Target ≤50 lines of output. Use tables for multi-resource comparisons.

Anti-Hallucination Rules

1. NEVER assume resource names — always discover via CLI/API in Phase 1 before referencing in Phase 2.
2. NEVER fabricate metric names or dimensions — verify against the service documentation or --help output.
3. NEVER mix CLI commands between service versions — confirm which version/API you are targeting.
4. ALWAYS use the discovery → verify → analyze chain — every resource referenced must have been discovered first.
5. ALWAYS handle empty results gracefully — an empty response is valid data, not an error to retry.

Counter-Rationalizations

Shortcut	Counter	Why
"I'll skip discovery and check known resources"	Always run Phase 1 discovery first	Resource names change, new resources appear — assumed names cause errors
"The user only asked for a quick check"	Follow the full discovery → analysis flow	Quick checks miss critical issues; structured analysis catches silent failures
"Default configuration is probably fine"	Audit configuration explicitly	Defaults often leave logging, security, and optimization features disabled
"Metrics aren't needed for this"	Always check relevant metrics when available	API/CLI responses show current state; metrics reveal trends and intermittent issues
"I don't have access to that"	Try the command and report the actual error	Assumed permission failures prevent useful investigation; actual errors are informative

Common Pitfalls

• Proxy not injected: Check namespace annotation linkerd.io/inject: enabled and restart pods
• TrafficSplit weights: Weights are relative, not percentages -- ensure they sum correctly
• Service profiles: Must match the FQDN format service.namespace.svc.cluster.local
• Control plane upgrades: Linkerd requires sequential minor version upgrades -- no skipping
• Opaque ports: Some protocols need config.linkerd.io/opaque-ports annotation for proper proxying