Alert thresholds depend on the nature of your applications. Some queries may have arbitrary tolerance thresholds. Building an efficient monitoring platform takes time. 😉
5 Prometheus alerting rules for Ruby. Exported via prometheus_exporter. These rules cover critical and warning conditions — copy and paste the YAML into your Prometheus configuration.
groups:
- name: RubyExporter
rules:
# Threshold is a rough default. Adjust based on your application's normal heap size.
- alert: RubyHeapLiveSlotsHigh
expr: ruby_heap_live_slots > 500000
for: 5m
labels:
severity: warning
annotations:
summary: Ruby heap live slots high (instance {{ $labels.instance }})
description: "Ruby heap has too many live slots (> 500k), heap bloat\n VALUE = {{ $value }}\n LABELS = {{ $labels }}"
- alert: RubyHeapFreeSlotsHigh
expr: ruby_heap_free_slots > 500000
for: 5m
labels:
severity: warning
annotations:
summary: Ruby heap free slots high (instance {{ $labels.instance }})
description: "Ruby heap has too many free slots (> 500k), memory fragmentation after large allocations\n VALUE = {{ $value }}\n LABELS = {{ $labels }}"
# Major GC rate > 5/s only fires if the app is essentially non-functional. Threshold of 2/s provides earlier detection.
- alert: RubyMajorGCRateHigh
expr: rate(ruby_major_gc_ops_total[5m]) > 2
for: 5m
labels:
severity: warning
annotations:
summary: Ruby major GC rate high (instance {{ $labels.instance }})
description: "Ruby is performing too many major GC cycles, indicating memory pressure\n VALUE = {{ $value }}\n LABELS = {{ $labels }}"
- alert: RubyRSSHigh
expr: ruby_rss > 1e9
for: 5m
labels:
severity: warning
annotations:
summary: Ruby RSS high (instance {{ $labels.instance }})
description: "Ruby process RSS is high (> 1GB)\n VALUE = {{ $value }}\n LABELS = {{ $labels }}"
- alert: RubyAllocatedObjectsSpike
expr: rate(ruby_allocated_objects_total[5m]) > 100000
for: 5m
labels:
severity: warning
annotations:
summary: Ruby allocated objects spike (instance {{ $labels.instance }})
description: "Ruby is allocating objects at a high rate\n VALUE = {{ $value }}\n LABELS = {{ $labels }}" wget https://raw.githubusercontent.com/samber/awesome-prometheus-alerts/refs/heads/master/dist/rules/ruby/ruby-exporter.yml
Ruby heap has too many live slots (> 500k), heap bloat
# Threshold is a rough default. Adjust based on your application's normal heap size.
- alert: RubyHeapLiveSlotsHigh
expr: ruby_heap_live_slots > 500000
for: 5m
labels:
severity: warning
annotations:
summary: Ruby heap live slots high (instance {{ $labels.instance }})
description: "Ruby heap has too many live slots (> 500k), heap bloat\n VALUE = {{ $value }}\n LABELS = {{ $labels }}" Ruby heap has too many free slots (> 500k), memory fragmentation after large allocations
- alert: RubyHeapFreeSlotsHigh
expr: ruby_heap_free_slots > 500000
for: 5m
labels:
severity: warning
annotations:
summary: Ruby heap free slots high (instance {{ $labels.instance }})
description: "Ruby heap has too many free slots (> 500k), memory fragmentation after large allocations\n VALUE = {{ $value }}\n LABELS = {{ $labels }}" Ruby is performing too many major GC cycles, indicating memory pressure
# Major GC rate > 5/s only fires if the app is essentially non-functional. Threshold of 2/s provides earlier detection.
- alert: RubyMajorGCRateHigh
expr: rate(ruby_major_gc_ops_total[5m]) > 2
for: 5m
labels:
severity: warning
annotations:
summary: Ruby major GC rate high (instance {{ $labels.instance }})
description: "Ruby is performing too many major GC cycles, indicating memory pressure\n VALUE = {{ $value }}\n LABELS = {{ $labels }}" Ruby process RSS is high (> 1GB)
- alert: RubyRSSHigh
expr: ruby_rss > 1e9
for: 5m
labels:
severity: warning
annotations:
summary: Ruby RSS high (instance {{ $labels.instance }})
description: "Ruby process RSS is high (> 1GB)\n VALUE = {{ $value }}\n LABELS = {{ $labels }}" Ruby is allocating objects at a high rate
- alert: RubyAllocatedObjectsSpike
expr: rate(ruby_allocated_objects_total[5m]) > 100000
for: 5m
labels:
severity: warning
annotations:
summary: Ruby allocated objects spike (instance {{ $labels.instance }})
description: "Ruby is allocating objects at a high rate\n VALUE = {{ $value }}\n LABELS = {{ $labels }}"