healthcheck/server.js

import express from 'express'
import Docker from 'dockerode'

const app = express()
const PORT = 8080
const docker = new Docker({ socketPath: '/var/run/docker.sock' })

async function getServiceStatusCode(service_name) {
  try {
    const service = docker.getService(service_name)
    await service.inspect()
    const tasks = await docker.listTasks({ filters: { service: [service_name] } })

    if (tasks.length === 0) {
      return 503
    }

    const isHealthy = tasks.some(task => {
      const state = task.Status.State
      const healthStatus = task.Status.ContainerStatus?.Health?.Status

      if (healthStatus === 'healthy' || (state === 'running' && !healthStatus)) {
        return true
      }

      return false
    })

    return isHealthy ? 200 : 503
  } catch (error) {
    console.error(error.message)

    if (error.statusCode === 404) {
      return 404
    }

    return 503
  }
}

app.get('/health/:service', async (req, res) => {
  const service = req.params.service

  if (!service || !/^[a-zA-Z0-9_-]+$/.test(service)) {
    return res.sendStatus(400)
  }

  const statusCode = await getServiceStatusCode(service)
  res.sendStatus(statusCode)
})

app.use((_, response) => response.sendStatus(404))

const server = app.listen(PORT, () => {
  console.log(`@syncraft/healthcheck listening on port ${PORT}`)
})

const shutdown_handler = (signal) => {
  console.log(`${signal} received. Initiating graceful shutdown.`)

  server.close((error) => {
    if (error) {
      console.error('Error during HTTP server close:', error)
      process.exit(1)
    }
    
    console.log('HTTP server closed. Exiting process.')
    process.exit(0)
  });
}

process.on('SIGTERM', () => shutdown_handler('SIGTERM'))
process.on('SIGINT', () => shutdown_handler('SIGINT'))