datahub/docs/advanced/monitoring.md

Monitoring DataHub

Overview

Monitoring DataHub's system components is essential for maintaining operational excellence, troubleshooting performance issues, and ensuring system reliability. This comprehensive guide covers how to implement observability in DataHub through tracing and metrics, and how to extract valuable insights from your running instances.

Why Monitor DataHub?

Effective monitoring enables you to:

• Identify Performance Bottlenecks: Pinpoint slow queries or API endpoints
• Debug Issues Faster: Trace requests across distributed components to locate failures
• Meet SLAs: Track and alert on key performance indicators

Observability Components

DataHub's observability strategy consists of two complementary approaches:

1. Metrics Collection

   Purpose: Aggregate statistical data about system behavior over time Technology: Transitioning from DropWizard/JMX to Micrometer

   Current State: DropWizard metrics exposed via JMX, collected by Prometheus Future Direction: Native Micrometer integration for Spring-based metrics Compatibility: Prometheus-compatible format with support for other metrics backends

   Key Metrics Categories:

   • Performance Metrics: Request latency, throughput, error rates
   • Resource Metrics: CPU, memory utilization
   • Application Metrics: Cache hit rates, queue depths, processing times
   • Business Metrics: Entity counts, ingestion rates, search performance

2. Distributed Tracing

   Purpose: Track individual requests as they flow through multiple services and components Technology: OpenTelemetry-based instrumentation

   • Provides end-to-end visibility of request lifecycles
   • Automatically instruments popular libraries (Kafka, JDBC, Elasticsearch)
   • Supports multiple backend systems (Jaeger, Zipkin, etc.)
   • Enables custom span creation with minimal code changes

   Key Benefits:

   • Visualize request flow across microservices
   • Identify latency hotspots
   • Understand service dependencies
   • Debug complex distributed transactions

GraphQL Instrumentation (Micrometer)

Overview

DataHub provides comprehensive instrumentation for its GraphQL API through Micrometer metrics, enabling detailed performance monitoring and debugging capabilities. The instrumentation system offers flexible configuration options to balance between observability depth and performance overhead.

Why Path-Level GraphQL Instrumentation Matters

Traditional GraphQL monitoring only tells you "the search query is slow" but not why. Without path-level instrumentation, you're blind to which specific fields are causing performance bottlenecks in complex nested queries.

Real-World Example

Consider this GraphQL query:

query getSearchResults {
  search(input: { query: "sales data" }) {
    searchResults {
      entity {
        ... on Dataset {
          name
          owner {
            # Path: /search/searchResults/entity/owner
            corpUser {
              displayName
            }
          }
          lineage {
            # Path: /search/searchResults/entity/lineage
            upstreamCount
            downstreamCount
            upstreamEntities {
              urn
              name
            }
          }
          schemaMetadata {
            # Path: /search/searchResults/entity/schemaMetadata
            fields {
              fieldPath
              description
            }
          }
        }
      }
    }
  }
}

What Path-Level Instrumentation Reveals

With path-level metrics, you discover:

• /search/searchResults/entity/owner - 50ms (fast, well-cached)
• /search/searchResults/entity/lineage - 2500ms (SLOW! hitting graph database)
• /search/searchResults/entity/schemaMetadata - 150ms (acceptable)

Without path metrics: "Search query takes 3 seconds"
With path metrics: "Lineage resolution is the bottleneck"

Key Benefits

1. Surgical Optimization

Instead of guessing, you know exactly which resolver needs optimization. Maybe lineage needs better caching or pagination.

2. Smart Query Patterns

Identify expensive patterns like:

# These paths consistently slow:
/*/lineage/upstreamEntities/*
/*/siblings/*/platform
# Action: Add field-level caching or lazy loading

3. Client-Specific Debugging

Different clients request different fields. Path instrumentation shows:

• Web UI requests are slow (requesting everything)
• API integrations timeout (requesting deep lineage)

4. N+1 Query Detection

Spot resolver patterns that indicate N+1 problems:

/users/0/permissions - 10ms
/users/1/permissions - 10ms
/users/2/permissions - 10ms
... (100 more times)

Configuration Strategy

Start targeted to minimize overhead:

# Focus on known slow operations
fieldLevelOperations: "searchAcrossEntities,getDataset"

# Target expensive resolver paths
fieldLevelPaths: "/**/lineage/**,/**/relationships/**,/**/privileges"

Architecture

The GraphQL instrumentation is implemented through GraphQLTimingInstrumentation, which extends GraphQL Java's instrumentation framework. It provides:

• Request-level metrics: Overall query performance and error tracking
• Field-level metrics: Detailed timing for individual field resolvers
• Smart filtering: Configurable targeting of specific operations or field paths
• Low overhead: Minimal performance impact through efficient instrumentation

Metrics Collected

Request-Level Metrics

Metric: graphql.request.duration

• Type: Timer with percentiles (p50, p95, p99)
• Tags:
  • operation: Operation name (e.g., "getSearchResultsForMultiple")
  • operation.type: Query, mutation, or subscription
  • success: true/false based on error presence
  • field.filtering: Filtering mode applied (DISABLED, ALL_FIELDS, BY_OPERATION, BY_PATH, BY_BOTH)
• Use Case: Monitor overall GraphQL performance, identify slow operations

Metric: graphql.request.errors

• Type: Counter
• Tags:
  • operation: Operation name
  • operation.type: Query, mutation, or subscription
• Use Case: Track error rates by operation

Field-Level Metrics

Metric: graphql.field.duration

• Type: Timer with percentiles (p50, p95, p99)
• Tags:
  • parent.type: GraphQL parent type (e.g., "Dataset", "User")
  • field: Field name being resolved
  • operation: Operation name context
  • success: true/false
  • path: Field path (optional, controlled by fieldLevelPathEnabled)
• Use Case: Identify slow field resolvers, optimize data fetching

Metric: graphql.field.errors

• Type: Counter
• Tags: Same as field duration (minus success tag)
• Use Case: Track field-specific error patterns

Metric: graphql.fields.instrumented

• Type: Counter
• Tags:
  • operation: Operation name
  • filtering.mode: Active filtering mode
• Use Case: Monitor instrumentation coverage and overhead

Configuration Guide

Master Controls

graphQL:
  metrics:
    # Master switch for all GraphQL metrics
    enabled: ${GRAPHQL_METRICS_ENABLED:true}

    # Enable field-level resolver metrics
    fieldLevelEnabled: ${GRAPHQL_METRICS_FIELD_LEVEL_ENABLED:false}

Selective Field Instrumentation

Field-level metrics can add significant overhead for complex queries. DataHub provides multiple strategies to control which fields are instrumented:

1. Operation-Based Filtering

Target specific GraphQL operations known to be slow or critical:

fieldLevelOperations: "getSearchResultsForMultiple,searchAcrossLineageStructure"

2. Path-Based Filtering

Use path patterns to instrument specific parts of your schema:

fieldLevelPaths: "/search/results/**,/user/*/permissions,/**/lineage/*"

Path Pattern Syntax:

• /user - Exact match for the user field
• /user/* - Direct children of user (e.g., /user/name, /user/email)
• /user/** - User field and all descendants at any depth
• /*/comments/* - Comments field under any parent

3. Combined Filtering

When both operation and path filters are configured, only fields matching BOTH criteria are instrumented:

# Only instrument search results within specific operations
fieldLevelOperations: "searchAcrossEntities"
fieldLevelPaths: "/searchResults/**"

Advanced Options

# Include field paths as metric tags (WARNING: high cardinality risk)
fieldLevelPathEnabled: false

# Include metrics for trivial property access
trivialDataFetchersEnabled: false

Filtering Modes Explained

The instrumentation automatically determines the most efficient filtering mode:

1. DISABLED: Field-level metrics completely disabled
2. ALL_FIELDS: No filtering, all fields instrumented (highest overhead)
3. BY_OPERATION: Only instrument fields within specified operations
4. BY_PATH: Only instrument fields matching path patterns
5. BY_BOTH: Most restrictive - both operation and path must match

Performance Considerations

Impact Assessment

Field-level instrumentation overhead varies by:

• Query complexity: More fields = more overhead
• Resolver performance: Fast resolvers have higher relative overhead
• Filtering effectiveness: Better targeting = less overhead

Best Practices

1. Start Conservative: Begin with field-level metrics disabled

   fieldLevelEnabled: false
   

2. Target Known Issues: Enable selectively for problematic operations

   fieldLevelEnabled: true
   fieldLevelOperations: "slowSearchQuery,complexLineageQuery"
   

3. Use Path Patterns Wisely: Focus on expensive resolver paths

   fieldLevelPaths: "/search/**,/**/lineage/**"
   

4. Avoid Path Tags in Production: High cardinality risk

   fieldLevelPathEnabled: false # Keep this false
   

5. Monitor Instrumentation Overhead: Track the graphql.fields.instrumented metric

Example Configurations

Development Environment (Full Visibility)

graphQL:
  metrics:
    enabled: true
    fieldLevelEnabled: true
    fieldLevelOperations: "" # All operations
    fieldLevelPathEnabled: true # Include paths for debugging
    trivialDataFetchersEnabled: true

Production - Targeted Monitoring

graphQL:
  metrics:
    enabled: true
    fieldLevelEnabled: true
    fieldLevelOperations: "getSearchResultsForMultiple,searchAcrossLineage"
    fieldLevelPaths: "/search/results/*,/lineage/upstream/**,/lineage/downstream/**"
    fieldLevelPathEnabled: false
    trivialDataFetchersEnabled: false

Production - Minimal Overhead

graphQL:
  metrics:
    enabled: true
    fieldLevelEnabled: false # Only request-level metrics

Debugging Slow Queries

When investigating GraphQL performance issues:

1. Enable request-level metrics first to identify slow operations
2. Temporarily enable field-level metrics for the slow operation:

   fieldLevelOperations: "problematicQuery"
   

3. Analyze field duration metrics to find bottlenecks
4. Optionally enable path tags (briefly) for precise identification:

   fieldLevelPathEnabled: true # Temporary only!
   

5. Optimize identified resolvers and disable detailed instrumentation

Integration with Monitoring Stack

The GraphQL metrics integrate seamlessly with DataHub's monitoring infrastructure:

• Prometheus: Metrics exposed at /actuator/prometheus
• Grafana: Create dashboards showing:
  • Request rates and latencies by operation
  • Error rates and types
  • Field resolver performance heatmaps
  • Top slow operations and fields

Example Prometheus queries:

# Average request duration by operation
rate(graphql_request_duration_seconds_sum[5m])
/ rate(graphql_request_duration_seconds_count[5m])

# Field resolver p99 latency
histogram_quantile(0.99,
  rate(graphql_field_duration_seconds_bucket[5m])
)

# Error rate by operation
rate(graphql_request_errors_total[5m])

Cache Monitoring (Micrometer)

Overview

Micrometer provides automatic instrumentation for cache implementations, offering deep insights into cache performance and efficiency. This instrumentation is crucial for DataHub, where caching significantly impacts query performance and system load.

Automatic Cache Metrics

When caches are registered with Micrometer, comprehensive metrics are automatically collected without code changes:

Core Metrics

• cache.size (Gauge) - Current number of entries in the cache
• cache.gets (Counter) - Cache access attempts, tagged with:
  • result=hit - Successful cache hits
  • result=miss - Cache misses requiring backend fetch
• cache.puts (Counter) - Number of entries added to cache
• cache.evictions (Counter) - Number of entries evicted
• cache.eviction.weight (Counter) - Total weight of evicted entries (for size-based eviction)

Derived Metrics

Calculate key performance indicators using Prometheus queries:

# Cache hit rate (should be >80% for hot caches)
sum(rate(cache_gets_total{result="hit"}[5m])) by (cache) /
sum(rate(cache_gets_total[5m])) by (cache)

# Cache miss rate
1 - (cache_hit_rate)

# Eviction rate (indicates cache pressure)
rate(cache_evictions_total[5m])

DataHub Cache Configuration

DataHub uses multiple cache layers, each automatically instrumented:

1. Entity Client Cache

cache.client.entityClient:
  enabled: true
  maxBytes: 104857600 # 100MB
  entityAspectTTLSeconds:
    corpuser:
      corpUserInfo: 20 # Short TTL for frequently changing data
      corpUserKey: 300 # Longer TTL for stable data
    structuredProperty:
      propertyDefinition: 300
      structuredPropertyKey: 86400 # 1 day for very stable data

2. Usage Statistics Cache

cache.client.usageClient:
  enabled: true
  maxBytes: 52428800 # 50MB
  defaultTTLSeconds: 86400 # 1 day
  # Caches expensive usage calculations

3. Search & Lineage Cache

cache.search.lineage:
  ttlSeconds: 86400 # 1 day

Monitoring Best Practices

Key Indicators to Watch

1. Hit Rate by Cache Type

   # Alert if hit rate drops below 70%
   cache_hit_rate < 0.7
   

2. Memory Pressure

   # High eviction rate relative to puts
   rate(cache_evictions_total[5m]) / rate(cache_puts_total[5m]) > 0.1
   

Thread Pool Executor Monitoring (Micrometer)

Overview

Micrometer automatically instruments Java ThreadPoolExecutor instances, providing crucial visibility into concurrency bottlenecks and resource utilization. For DataHub's concurrent operations, this monitoring is essential for maintaining performance under load.

Automatic Executor Metrics

Pool State Metrics

• executor.pool.size (Gauge) - Current number of threads in pool
• executor.pool.core (Gauge) - Core (minimum) pool size
• executor.pool.max (Gauge) - Maximum allowed pool size
• executor.active (Gauge) - Threads actively executing tasks

Queue Metrics

• executor.queued (Gauge) - Tasks waiting in queue
• executor.queue.remaining (Gauge) - Available queue capacity

Performance Metrics

• executor.completed (Counter) - Total completed tasks
• executor.seconds (Timer) - Task execution time distribution
• executor.rejected (Counter) - Tasks rejected due to saturation

DataHub Executor Configurations

1. GraphQL Query Executor

graphQL.concurrency:
  separateThreadPool: true
  corePoolSize: 20 # Base threads
  maxPoolSize: 200 # Scale under load
  keepAlive: 60 # Seconds before idle thread removal
  # Handles complex GraphQL query resolution

2. Batch Processing Executors

entityClient.restli:
  get:
    batchConcurrency: 2 # Parallel batch processors
    batchQueueSize: 500 # Task buffer
    batchThreadKeepAlive: 60
  ingest:
    batchConcurrency: 2
    batchQueueSize: 500

3. Search & Analytics Executors

timeseriesAspectService.query:
  concurrency: 10 # Parallel query threads
  queueSize: 500 # Buffered queries

Critical Monitoring Patterns

Saturation Detection

# Thread pool utilization (>0.8 indicates pressure)
executor_active / executor_pool_size > 0.8

# Queue filling up (>0.7 indicates backpressure)
executor_queued / (executor_queued + executor_queue_remaining) > 0.7

Rejection & Starvation

# Task rejections (should be zero)
rate(executor_rejected_total[1m]) > 0

# Thread starvation (all threads busy for extended period)
avg_over_time(executor_active[5m]) >= executor_pool_core

Performance Analysis

# Average task execution time
rate(executor_seconds_sum[5m]) / rate(executor_seconds_count[5m])

# Task throughput by executor
rate(executor_completed_total[5m])

Tuning Guidelines

Symptoms & Solutions

Symptom	Metric Pattern	Solution
High latency	executor_queued rising	Increase pool size
Rejections	executor_rejected > 0	Increase queue size or pool max
Memory pressure	Many idle threads	Reduce keepAlive time
CPU waste	Low executor_active	Reduce core pool size

Capacity Planning

1. Measure baseline: Monitor under normal load
2. Stress test: Identify saturation points
3. Set alerts:
   • Warning at 70% utilization
   • Critical at 90% utilization
4. Auto-scale: Consider dynamic pool sizing based on queue depth

Distributed Tracing

Traces let us track the life of a request across multiple components. Each trace is consisted of multiple spans, which are units of work, containing various context about the work being done as well as time taken to finish the work. By looking at the trace, we can more easily identify performance bottlenecks.

We enable tracing by using the OpenTelemetry java instrumentation library. This project provides a Java agent JAR that is attached to java applications. The agent injects bytecode to capture telemetry from popular libraries.

Using the agent we are able to

1. Plug and play different tracing tools based on the user's setup: Jaeger, Zipkin, or other tools
2. Get traces for Kafka, JDBC, and Elasticsearch without any additional code
3. Track traces of any function with a simple @WithSpan annotation

You can enable the agent by setting env variable ENABLE_OTEL to true for GMS and MAE/MCE consumers. In our example docker-compose, we export metrics to a local Jaeger instance by setting env variable OTEL_TRACES_EXPORTER to jaeger and OTEL_EXPORTER_JAEGER_ENDPOINT to http://jaeger-all-in-one:14250, but you can easily change this behavior by setting the correct env variables. Refer to this doc for all configs.

Once the above is set up, you should be able to see a detailed trace as a request is sent to GMS. We added the @WithSpan annotation in various places to make the trace more readable. You should start to see traces in the tracing collector of choice. Our example docker-compose deploys an instance of Jaeger with port 16686. The traces should be available at http://localhost:16686.

Configuration Note

We recommend using either grpc or http/protobuf, configured using OTEL_EXPORTER_OTLP_PROTOCOL. Avoid using http will not work as expected due to the size of the generated spans.

Micrometer

DataHub is transitioning to Micrometer as its primary metrics framework, representing a significant upgrade in observability capabilities. Micrometer is a vendor-neutral application metrics facade that provides a simple, consistent API for the most popular monitoring systems, allowing you to instrument your JVM-based application code without vendor lock-in.

Why Micrometer?

1. Native Spring Integration

   As DataHub uses Spring Boot, Micrometer provides seamless integration with:

   • Auto-configuration of common metrics
   • Built-in metrics for HTTP requests, JVM, caches, and more
   • Spring Boot Actuator endpoints for metrics exposure
   • Automatic instrumentation of Spring components

2. Multi-Backend Support

   Unlike the legacy DropWizard approach that primarily targets JMX, Micrometer natively supports:

   • Prometheus (recommended for cloud-native deployments)
   • JMX (for backward compatibility)
   • StatsD
   • CloudWatch
   • Datadog
   • New Relic
   • And many more...

3. Dimensional Metrics

   Micrometer embraces modern dimensional metrics with labels/tags, enabling:

   • Rich querying and aggregation capabilities
   • Better cardinality control
   • More flexible dashboards and alerts
   • Natural integration with cloud-native monitoring systems

Micrometer Transition Plan

DataHub is undertaking a strategic transition from DropWizard metrics (exposed via JMX) to Micrometer, a modern vendor-neutral metrics facade. This transition aims to provide better cloud-native monitoring capabilities while maintaining backward compatibility for existing monitoring infrastructure.

Current State

What We Have Now:

• Primary System: DropWizard metrics exposed through JMX
• Collection Method: Prometheus-JMX exporter scrapes JMX metrics
• Dashboards: Grafana dashboards consuming JMX-sourced metrics
• Code Pattern: MetricUtils class for creating counters and timers
• Integration: Basic Spring integration with manual metric creation

Limitations:

• JMX-centric approach limits monitoring backend options
• No unified observability (separate instrumentation for metrics and traces)
• No support for dimensional metrics and tags
• Manual instrumentation required for most components
• Legacy naming conventions without proper tagging

Transition State

What We're Building:

• Primary System: Micrometer with native Prometheus support
• Collection Method: Direct Prometheus scraping via /actuator/prometheus
• Unified Telemetry: Single instrumentation point for both metrics and traces
• Modern Patterns: Dimensional metrics with rich tagging
• Multi-Backend: Support for Prometheus, StatsD, CloudWatch, Datadog, etc.
• Auto-Instrumentation: Automatic metrics for Spring components

Key Decisions and Rationale:

1. Dual Registry Approach

   Decision: Run both systems in parallel with tag-based routing

   Rationale:

   • Zero downtime or disruption
   • Gradual migration at component level
   • Easy rollback if issues arise

2. Prometheus as Primary Target

   Decision: Focus on Prometheus for new metrics

   Rationale:

   • Industry standard for cloud-native applications
   • Rich query language and ecosystem
   • Better suited for dimensional metrics

3. Observation API Adoption

   Decision: Promote Observation API for new instrumentation

   Rationale:

   • Single instrumentation for metrics + traces
   • Reduced code complexity
   • Consistent naming across telemetry types

Future State

Once fully adopted, Micrometer will transform DataHub's observability from a collection of separate tools into a unified platform. This means developers can focus on building features while getting comprehensive telemetry "for free."

Intelligent and Adaptive Monitoring

• Dynamic Instrumentation: Enable detailed metrics for specific entities or operations on-demand without code changes
• Environment-Aware Metrics: Automatically route metrics to Prometheus in Kubernetes, CloudWatch in AWS, or Azure Monitor in Azure
• Built-in SLO Tracking: Define Service Level Objectives declaratively and automatically track error budgets

Developer and Operator Experience

• Adding @Observed to a method automatically generates latency percentiles, error rates, and distributed trace spans
• Every service exposes golden signals (latency, traffic, errors, saturation) out-of-the-box
• Business metrics (entity ingestion rates, search performance) seamlessly correlate with system metrics
• Self-documenting telemetry where metrics, traces, and logs tell a coherent operational story

DropWizard & JMX

We originally decided to use Dropwizard Metrics to export custom metrics to JMX, and then use Prometheus-JMX exporter to export all JMX metrics to Prometheus. This allows our code base to be independent of the metrics collection tool, making it easy for people to use their tool of choice. You can enable the agent by setting env variable ENABLE_PROMETHEUS to true for GMS and MAE/MCE consumers. Refer to this example docker-compose for setting the variables.

In our example docker-compose, we have configured prometheus to scrape from 4318 ports of each container used by the JMX exporter to export metrics. We also configured grafana to listen to prometheus and create useful dashboards. By default, we provide two dashboards: JVM dashboard and DataHub dashboard.

In the JVM dashboard, you can find detailed charts based on JVM metrics like CPU/memory/disk usage. In the DataHub dashboard, you can find charts to monitor each endpoint and the kafka topics. Using the example implementation, go to http://localhost:3001 to find the grafana dashboards! (Username: admin, PW: admin)

To make it easy to track various metrics within the code base, we created MetricUtils class. This util class creates a central metric registry, sets up the JMX reporter, and provides convenient functions for setting up counters and timers. You can run the following to create a counter and increment.

metricUtils.counter(this.getClass(),"metricName").increment();

You can run the following to time a block of code.

try(Timer.Context ignored=metricUtils.timer(this.getClass(),"timerName").timer()){
    ...block of code
    }

Enable monitoring through docker-compose

We provide some example configuration for enabling monitoring in this directory. Take a look at the docker-compose files, which adds necessary env variables to existing containers, and spawns new containers (Jaeger, Prometheus, Grafana).

You can add in the above docker-compose using the -f <<path-to-compose-file>> when running docker-compose commands. For instance,

docker-compose \
  -f quickstart/docker-compose.quickstart.yml \
  -f monitoring/docker-compose.monitoring.yml \
  pull && \
docker-compose -p datahub \
  -f quickstart/docker-compose.quickstart.yml \
  -f monitoring/docker-compose.monitoring.yml \
  up

We set up quickstart.sh, dev.sh, and dev-without-neo4j.sh to add the above docker-compose when MONITORING=true. For instance MONITORING=true ./docker/quickstart.sh will add the correct env variables to start collecting traces and metrics, and also deploy Jaeger, Prometheus, and Grafana. We will soon support this as a flag during quickstart.

Health check endpoint

For monitoring healthiness of your DataHub service, /admin endpoint can be used.