Application Services Skill

Monitor application service performance, health, and runtime-specific metrics using DQL.

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Core Capabilities

1. Service Performance (RED Metrics)

Monitor service Rate, Errors, Duration using metrics-based timeseries queries.

Key Metrics:

• dt.service.request.response_time - Response time (microseconds)
• dt.service.request.count - Request count
• dt.service.request.failure_count - Failed request count

Common Use Cases:

• Response time monitoring (avg, p50, p95, p99)
• Error rate tracking and spike detection
• Traffic analysis (throughput, peaks, growth)
• Performance degradation detection
• Multi-cluster comparison

Quick Example:

timeseries {
  p95 = percentile(dt.service.request.response_time, 95),
  total_requests = sum(dt.service.request.count),
  failures = sum(dt.service.request.failure_count)
}, by: {dt.service.name}
| fieldsAdd p95_ms = p95[] / 1000, error_rate_pct = (failures[] * 100.0) / total_requests[]

→ For detailed queries: See references/service-metrics.md

2. Advanced Service Analysis

Span-based queries for complex scenarios requiring flexible filtering and custom aggregations.

Use Cases:

• SLA compliance tracking with custom thresholds
• Service health scoring (multi-dimensional)
• Operation/endpoint-level performance analysis
• Custom error classification
• Failure pattern detection with error details

Quick Example:

fetch spans, from: now() - 1h | filter request.is_root_span == true
| fieldsAdd meets_sla = if(request.is_failed == false AND duration < 3s, 1, else: 0)
| summarize total = count(), sla_compliant = sum(meets_sla), by: {dt.service.name}
| fieldsAdd sla_compliance_pct = (sla_compliant * 100.0) / total

→ For detailed queries: See references/service-metrics.md

3. Service Messaging Metrics

Monitor message-based service communication (queues, topics).

Key Metrics:

• dt.service.messaging.publish.count - Messages sent to queues or topics
• dt.service.messaging.receive.count - Messages received from queues or topics
• dt.service.messaging.process.count - Messages successfully processed
• dt.service.messaging.process.failure_count - Messages that failed processing

Use Cases:

• Message throughput monitoring (publish/receive rates)
• Message processing failure tracking
• Queue/topic health analysis
• Consumer lag detection (publish vs receive rate comparison)

Quick Example:

timeseries {
  published = sum(dt.service.messaging.publish.count),
  received = sum(dt.service.messaging.receive.count),
  processed = sum(dt.service.messaging.process.count),
  failed = sum(dt.service.messaging.process.failure_count)
}, by: {dt.service.name}

→ For detailed queries: See references/service-metrics.md

4. Service Mesh Monitoring

Monitor service mesh ingress performance and overhead.

Key Metrics:

• dt.service.request.service_mesh.response_time - Mesh response time (microseconds)
• dt.service.request.service_mesh.count - Mesh request count
• dt.service.request.service_mesh.failure_count - Mesh failure count

Use Cases:

• Mesh vs direct performance comparison
• Mesh overhead calculation
• Mesh failure analysis
• gRPC traffic monitoring
• Multi-cluster mesh performance

Quick Example:

timeseries {
  direct_p95 = percentile(dt.service.request.response_time, 95),
  mesh_p95 = percentile(dt.service.request.service_mesh.response_time, 95)
}, by: {dt.service.name}
| fieldsAdd mesh_overhead_ms = (mesh_p95[] - direct_p95[]) / 1000

→ For detailed queries: See references/service-metrics.md

5. Runtime-Specific Monitoring

Technology-specific runtime performance and resource usage metrics.

Java/JVM - references/java.md

• Memory: heap, pools, metaspace
• GC: impact, suspension, frequency, pause time
• Threads: count monitoring, leak detection
• Classes: loading, unloading, growth

Node.js - references/nodejs.md

• Event loop: utilization, active handles
• V8 heap: memory used, total
• GC: collection time, suspension
• Process: RSS memory

.NET CLR - references/dotnet.md

• Memory: consumption by generation
• GC: collection count, suspension time
• Thread pool: threads, queued work
• JIT: compilation time

Python - references/python.md

• Threads: active thread count
• Heap: allocated blocks
• GC: collection by generation, pause time
• Objects: collected, uncollectable

PHP - references/php.md

• OPcache: hit ratio, memory, restarts
• GC: effectiveness, duration
• JIT: buffer usage
• Interned strings: usage, buffer

Go - references/go.md

• Goroutines: count, leak detection
• GC: suspension, collection time
• Memory: heap by state, committed
• Scheduler: worker threads, queue size
• CGo: call frequency

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When to Use This Skill

✅ Use for:

• Monitoring service performance (response time, errors, traffic)
• Calculating SLA compliance
• Analyzing service mesh performance
• Monitoring messaging throughput and processing failures
• Troubleshooting runtime-specific issues (GC, memory, threads)
• Multi-cluster service comparison
• Operation/endpoint-level analysis

❌ Don't use for:

• Infrastructure metrics (use infrastructure skills)
• Log analysis (use logs skills)
• Distributed tracing workflows (use traces/spans skills)
• Database performance (use database skills)

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Agent Instructions

Understanding User Intent

Map user questions to capabilities:

User Request	Use Capability	Key Files
"service performance", "response time", "error rate"	Service Performance (RED)	service-metrics.md
"SLA tracking", "health scoring"	Advanced Service Analysis	service-metrics.md
"service mesh", "Istio", "Linkerd", "mesh overhead"	Service Mesh Monitoring	service-metrics.md
"messaging", "queue", "topic", "publish", "consumer"	Service Messaging Metrics	service-metrics.md
"JVM GC", "Java memory", "heap"	Runtime-Specific (Java)	java.md
"Node.js event loop", "V8 heap"	Runtime-Specific (Node.js)	nodejs.md
".NET CLR", "GC generation"	Runtime-Specific (.NET)	dotnet.md
"Python GC", "thread count"	Runtime-Specific (Python)	python.md
"OPcache", "PHP GC"	Runtime-Specific (PHP)	php.md
"goroutines", "Go GC", "scheduler"	Runtime-Specific (Go)	go.md

Query Construction Patterns

1. Metrics-based (timeseries)

• Use for: Standard monitoring, dashboards, alerting
• Pattern: timeseries <metric> = <aggregation>(<metric_name>), by: {dimensions}
• Files: service-metrics.md, all runtime-specific files

2. Span-based (fetch spans)

• Use for: Complex filtering, custom logic, detailed analysis
• Pattern: fetch spans | filter request.is_root_span == true | fieldsAdd ... | summarize ...
• Files: service-metrics.md (Advanced Service Analysis section)

3. Comparison queries

• Use append for baseline comparison
• Use shift: -15m for time-shifted baselines
• Example: Performance degradation detection

Response Construction Guidelines

Always include:

1. Metric name(s) - Clear metric identifiers
2. Aggregation - How data is aggregated (avg, sum, percentile)
3. Grouping - Dimensions used (dt.service.name, k8s.workload.name, etc.)
4. Unit conversion - Convert microseconds to milliseconds where appropriate
5. Filtering - Relevant thresholds or conditions

When referencing runtime-specific content:

• Check user's technology stack first
• Provide only relevant runtime queries (don't overwhelm with all 6 runtimes)
• Explain runtime-specific metrics (e.g., "OPcache hit ratio" measures PHP opcode cache efficiency)

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Common Workflows

Workflow: Service Health Check

1. Check response time (RED metrics)
2. Check error rate (RED metrics)
3. Check traffic patterns (RED metrics)
4. If runtime-specific issues suspected → Load runtime-specific reference

Workflow: SLA Monitoring

1. Define SLA criteria (e.g., < 3s response time AND < 1% error rate)
2. Use span-based query for custom SLA logic
3. Calculate compliance percentage
4. Filter non-compliant services

Workflow: Service Mesh Analysis

1. Check mesh response time
2. Compare mesh vs direct performance
3. Calculate mesh overhead
4. Analyze mesh failure rates

Workflow: Runtime Troubleshooting

1. Identify technology stack → Load runtime-specific reference
2. Check memory/GC metrics → threads/goroutines → runtime features

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References

Core Service Monitoring:

• references/service-metrics.md - Complete RED metrics, SLA tracking, service mesh queries

Runtime-Specific Monitoring:

• references/java.md - Java/JVM monitoring
• references/nodejs.md - Node.js monitoring
• references/dotnet.md - .NET CLR monitoring
• references/python.md - Python monitoring
• references/php.md - PHP monitoring
• references/go.md - Go runtime monitoring