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README.md

LOOP Plugins

⚠️ Experimental ⚠️

This directory supports Local-Out-Of-Process (LOOP) Plugins, an alternative node runtime where some systems execute in separate processes, plug-in via github.com/hashicorp/go-plugin, and communicate via GRPC.

There are currently two kinds of plugins, and one implementation of each: a Solana Relayer plugin, and a Median Reporting plugin. The cmd directory contains their package mains for now. These can be built via make install-solana and make install-median.

How to use

chainlink.Dockerfile extends the regular core/chainlink.Dockerfile to include the plugin binaries, and enables support by setting CL_SOLANA_CMD, CL_STARKNET_CMD, and CL_MEDIAN_CMD. Either plugin can be disabled by un-setting the environment variable, which will revert to the original in-process runtime. Images built from this Dockerfile can otherwise be used normally, provided that the pre-requisites have been met.

Pre-requisites

Timeouts

LOOPPs communicate over GRPC, which always includes a context.Context and requires realistic timeouts. Placeholder/dummy values (e.g. MaxDurationQuery = 0) will not work and must be updated to realistic values. In lieu of reconfiguring already deployed contracts on Solana, the environment variable CL_MIN_OCR2_MAX_DURATION_QUERY can be set establish a new minimum via libocr's LocalConfig.MinOCR2MaxDurationQuery. If left unset, the default value is 100ms.

Prometheus

LOOPPs are dynamic, and so must be monitoring. We use Plugin discovery to dynamically determine what to monitor based on what plugins are running and we route external prom scraping to the plugins without exposing them directly

The endpoints are

/discovery : HTTP Service Discovery [https://prometheus.io/docs/prometheus/latest/configuration/configuration/#http_sd_config] Prometheus server is configured to poll this url to discover new endpoints to monitor. The node serves the response based on what plugins are running,

/plugins/<name>/metrics: The node acts as very thin middleware to route from Prometheus server scrape requests to individual plugin /metrics endpoint Once a plugin is discovered via the discovery mechanism above, the Prometheus service calls the target endpoint at the scrape interval The node acts as middleware to route the request to the /metrics endpoint of the requested plugin

The simplest change to monitor LOOPPs is to add a service discovery to the scrape configuration

  • job_name: 'chainlink_node' ...
  • http_sd_configs:
  •  - url: "http://127.0.0.1:6688/discovery"

  •    refresh_interval: 30s

See the Prometheus documentation for full details [https://prometheus.io/docs/prometheus/latest/configuration/configuration/#http_sd_config]