Analyzing Vitess

Vitess Analysis Skill

Analyze and optimize Vitess clusters with safe, read-only operations.

MANDATORY: Two-Phase Execution

You MUST follow this two-phase pattern. Skipping Phase 1 causes hallucinated keyspace/table names.

Phase 1: Discovery (ALWAYS run first)

#!/bin/bash

# 1. List cells
vtctldclient GetCellInfoNames

# 2. List keyspaces
vtctldclient GetKeyspaces

# 3. Get keyspace info
vtctldclient GetKeyspace my_keyspace

# 4. List tablets
vtctldclient GetTablets --keyspace my_keyspace

# 5. Get VSchema (table routing)
vtctldclient GetVSchema my_keyspace

# 6. List shards
vtctldclient FindAllShardsInKeyspace my_keyspace

Phase 1 outputs:

• Cells, keyspaces, and shards
• Tablet list with types and health
• VSchema with table definitions

Phase 2: Analysis (only after Phase 1)

Only reference keyspaces, shards, and tables confirmed in Phase 1.

Shell Script Patterns

Helper Function

#!/bin/bash

# Core vtctldclient helper — always use this
vtctl() {
    vtctldclient --server "${VTCTLD_SERVER:-localhost:15999}" "$@"
}

# VTGate SQL helper
vt_query() {
    local query="$1"
    mysql -h "${VTGATE_HOST:-localhost}" -P "${VTGATE_PORT:-15306}" \
        -u "${VTGATE_USER:-}" -e "$query"
}

Anti-Hallucination Rules

• NEVER reference a keyspace without confirming via GetKeyspaces
• NEVER reference table names without checking VSchema or running SHOW TABLES via VTGate
• NEVER assume shard names — always get from FindAllShardsInKeyspace
• NEVER guess tablet aliases — always list via GetTablets
• NEVER assume VIndex types — always check VSchema

Safety Rules

• READ-ONLY ONLY: Use only Get*, Find*, SELECT, SHOW commands
• FORBIDDEN: ApplySchema, ApplyVSchema, Reshard, MoveTables without explicit user request
• ALWAYS verify tablet health before querying specific tablets
• Use VTGate for queries — never query tablets directly unless debugging

Common Operations

Cluster Health Overview

#!/bin/bash
echo "=== Cells ==="
vtctl GetCellInfoNames

echo ""
echo "=== Keyspaces ==="
for KS in $(vtctl GetKeyspaces); do
    echo "--- $KS ---"
    vtctl GetKeyspace "$KS" | jq '{name, keyspace_type, durability_policy}'
done

echo ""
echo "=== Tablets ==="
vtctl GetTablets | jq -r '.[] | "\(.tablet.alias.cell)/\(.tablet.alias.uid)\t\(.tablet.keyspace)\t\(.tablet.shard)\t\(.tablet.type)\t\(.state)"'

Tablet Health Analysis

#!/bin/bash
KEYSPACE="${1:-my_keyspace}"

echo "=== Tablet Health for $KEYSPACE ==="
vtctl GetTablets --keyspace "$KEYSPACE" | jq '.[] | {alias: "\(.tablet.alias.cell)/\(.tablet.alias.uid)", type: .tablet.type, shard: .tablet.shard, hostname: .tablet.hostname, state: .state}'

echo ""
echo "=== Shard Info ==="
vtctl FindAllShardsInKeyspace "$KEYSPACE" | jq '.shards | to_entries[] | {shard: .key, primary_alias: .value.primary_alias, is_primary_serving: .value.is_primary_serving}'

echo ""
echo "=== Replication Status ==="
for TABLET in $(vtctl GetTablets --keyspace "$KEYSPACE" | jq -r '.[] | "\(.tablet.alias.cell)-\(.tablet.alias.uid)"'); do
    echo "--- $TABLET ---"
    vtctl GetReplicationStatus "$TABLET" 2>/dev/null
done

VSchema & Routing Analysis

#!/bin/bash
KEYSPACE="${1:-my_keyspace}"

echo "=== VSchema ==="
vtctl GetVSchema "$KEYSPACE" | jq '{tables: (.tables | keys), vindexes: (.vindexes | keys)}'

echo ""
echo "=== Routing Rules ==="
vtctl GetRoutingRules | jq '.'

echo ""
echo "=== Shard Routing ==="
vtctl GetShardRoutingRules 2>/dev/null | jq '.'

VReplication & Resharding Status

#!/bin/bash
echo "=== Active VReplication Workflows ==="
vtctl GetWorkflows my_keyspace | jq '.workflows[]? | {name, state, source, target, max_v_replication_lag}'

echo ""
echo "=== Reshard Status ==="
vtctl Reshard --target-keyspace my_keyspace status 2>/dev/null || echo "No active reshard"

echo ""
echo "=== MoveTables Status ==="
vtctl MoveTables --target-keyspace my_keyspace status 2>/dev/null || echo "No active MoveTables"

Output Format

Present results as a structured report:

Analyzing Vitess 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.

Counter-Rationalizations

Common Pitfalls

• Scatter queries: Queries without VIndex-routable WHERE clauses scatter to all shards — very expensive
• VSchema misconfig: Missing VIndex definitions cause scatter queries — always verify VSchema
• Primary tablet failover: Monitor primary tablet health — failover causes brief unavailability
• Resharding in progress: Active resharding adds replication lag — monitor VReplication lag
• Schema changes: Use Vitess schema management (ApplySchema) — direct DDL can cause inconsistency
• Cross-shard joins: Vitess does not support cross-shard joins natively — plan VSchema accordingly