@loopback/docs

# @loopback/extension-metrics This module contains a component that reports metrics of Node.js, LoopBack framework, and your application to [Prometheus](https://prometheus.io/). ## Stability: ⚠️Experimental⚠️ > Experimental packages provide early access to advanced or experimental > functionality to get community feedback. Such modules are published to npm > using `0.x.y` versions. Their APIs and functionality may be subject to > breaking changes in future releases. ## Installation ```sh npm install --save @loopback/extension-metrics ``` ## Basic use The component should be loaded in the constructor of your custom Application class. Start by importing the component class: ```ts import {MetricsComponent} from '@loopback/extension-metrics'; ``` In the constructor, add the component to your application: ```ts this.component(MetricsComponent); ``` By default, Metrics route is mounted at `/metrics`. This path can be customized via Metrics configuration as follows: ```ts this.configure(MetricsBindings.COMPONENT).to({ endpoint: { basePath: '/metrics', }, defaultMetrics: { timeout: 5000, }, }); ``` ## Metrics Collected There are three types of metrics being collected by this component: 1. Node.js metrics - built-in by https://github.com/siimon/prom-client 2. LoopBack method invocations - built-in by this module using an interceptor 3. Metrics by the application code or other modules - instrumentations are required ## Pull vs Push Prometheus supports two modes to collect metrics: - pull - scraping from metrics http endpoint exposed by the system being monitored - push - pushing metrics from the system being monitored to a push gateway See https://prometheus.io/docs/introduction/faq/#why-do-you-pull-rather-than-push ## Try it out ```sh git clone https://github.com/strongloop/loopback-next npm install npm run build cd examples/metrics-prometheus npm run demo ``` Open http://localhost:9090 to load Prometheus web UI. ### /metrics endpoint http://localhost:3000/metrics returns metrics in plain text format. It includes information for the Node.js process as well as LoopBack method invocations. <details> <summary markdown="span">Example of plain text data</summary> <pre> # HELP process_cpu_user_seconds_total Total user CPU time spent in seconds. # TYPE process_cpu_user_seconds_total counter process_cpu_user_seconds_total 0.132181 1564508354524 # HELP process_cpu_system_seconds_total Total system CPU time spent in seconds. # TYPE process_cpu_system_seconds_total counter process_cpu_system_seconds_total 0.023608999999999998 1564508354524 # HELP process_cpu_seconds_total Total user and system CPU time spent in seconds. # TYPE process_cpu_seconds_total counter process_cpu_seconds_total 0.15578999999999998 1564508354524 # HELP process_start_time_seconds Start time of the process since unix epoch in seconds. # TYPE process_start_time_seconds gauge process_start_time_seconds 1564508343 # HELP process_resident_memory_bytes Resident memory size in bytes. # TYPE process_resident_memory_bytes gauge process_resident_memory_bytes 61800448 1564508354524 # HELP nodejs_eventloop_lag_seconds Lag of event loop in seconds. # TYPE nodejs_eventloop_lag_seconds gauge nodejs_eventloop_lag_seconds 0.002172946 1564508354526 # HELP nodejs_active_handles Number of active libuv handles grouped by handle type. Every handle type is C++ class name. # TYPE nodejs_active_handles gauge nodejs_active_handles{type="WriteStream"} 2 1564508354524 nodejs_active_handles{type="Server"} 1 1564508354524 nodejs_active_handles{type="Socket"} 2 1564508354524 # HELP nodejs_active_handles_total Total number of active handles. # TYPE nodejs_active_handles_total gauge nodejs_active_handles_total 5 1564508354526 # HELP nodejs_active_requests Number of active libuv requests grouped by request type. Every request type is C++ class name. # TYPE nodejs_active_requests gauge # HELP nodejs_active_requests_total Total number of active requests. # TYPE nodejs_active_requests_total gauge nodejs_active_requests_total 0 1564508354526 # HELP nodejs_heap_size_total_bytes Process heap size from node.js in bytes. # TYPE nodejs_heap_size_total_bytes gauge nodejs_heap_size_total_bytes 27545600 1564508354526 # HELP nodejs_heap_size_used_bytes Process heap size used from node.js in bytes. # TYPE nodejs_heap_size_used_bytes gauge nodejs_heap_size_used_bytes 23788272 1564508354526 # HELP nodejs_external_memory_bytes Nodejs external memory size in bytes. # TYPE nodejs_external_memory_bytes gauge nodejs_external_memory_bytes 1234918 1564508354526 # HELP nodejs_heap_space_size_total_bytes Process heap space size total from node.js in bytes. # TYPE nodejs_heap_space_size_total_bytes gauge nodejs_heap_space_size_total_bytes{space="read_only"} 524288 1564508354526 nodejs_heap_space_size_total_bytes{space="new"} 1048576 1564508354526 nodejs_heap_space_size_total_bytes{space="old"} 16900096 1564508354526 nodejs_heap_space_size_total_bytes{space="code"} 688128 1564508354526 nodejs_heap_space_size_total_bytes{space="map"} 1576960 1564508354526 nodejs_heap_space_size_total_bytes{space="large_object"} 6758400 1564508354526 nodejs_heap_space_size_total_bytes{space="code_large_object"} 49152 1564508354526 nodejs_heap_space_size_total_bytes{space="new_large_object"} 0 1564508354526 # HELP nodejs_heap_space_size_used_bytes Process heap space size used from node.js in bytes. # TYPE nodejs_heap_space_size_used_bytes gauge nodejs_heap_space_size_used_bytes{space="read_only"} 31712 1564508354526 nodejs_heap_space_size_used_bytes{space="new"} 9584 1564508354526 nodejs_heap_space_size_used_bytes{space="old"} 15723128 1564508354526 nodejs_heap_space_size_used_bytes{space="code"} 377600 1564508354526 nodejs_heap_space_size_used_bytes{space="map"} 918480 1564508354526 nodejs_heap_space_size_used_bytes{space="large_object"} 6726408 1564508354526 nodejs_heap_space_size_used_bytes{space="code_large_object"} 3456 1564508354526 nodejs_heap_space_size_used_bytes{space="new_large_object"} 0 1564508354526 # HELP nodejs_heap_space_size_available_bytes Process heap space size available from node.js in bytes. # TYPE nodejs_heap_space_size_available_bytes gauge nodejs_heap_space_size_available_bytes{space="read_only"} 492264 1564508354526 nodejs_heap_space_size_available_bytes{space="new"} 1038368 1564508354526 nodejs_heap_space_size_available_bytes{space="old"} 1105240 1564508354526 nodejs_heap_space_size_available_bytes{space="code"} 285952 1564508354526 nodejs_heap_space_size_available_bytes{space="map"} 657072 1564508354526 nodejs_heap_space_size_available_bytes{space="large_object"} 0 1564508354526 nodejs_heap_space_size_available_bytes{space="code_large_object"} 0 1564508354526 nodejs_heap_space_size_available_bytes{space="new_large_object"} 1047952 1564508354526 # HELP nodejs_version_info Node.js version info. # TYPE nodejs_version_info gauge nodejs_version_info{version="v12.4.0",major="12",minor="4",patch="0"} 1 # HELP loopback_invocation_duration_seconds method invocation # TYPE loopback_invocation_duration_seconds gauge # HELP loopback_invocation_duration_histogram method invocation histogram # TYPE loopback_invocation_duration_histogram histogram # HELP loopback_invocation_total method invocation counts # TYPE loopback_invocation_total counter loopback_invocation_total 1 # HELP loopback_invocation_duration_summary method invocation summary # TYPE loopback_invocation_duration_summary summary </pre> </details> ## Contributions - [Guidelines](https://github.com/strongloop/loopback-next/blob/master/docs/CONTRIBUTING.md) - [Join the team](https://github.com/strongloop/loopback-next/issues/110) ## Tests Run `npm test` from the root folder. ## Contributors See [all contributors](https://github.com/strongloop/loopback-next/graphs/contributors). ## License MIT