import lndService from 'ln-service' import lnd from '@/api/lnd' const cache = new Map() const expiresIn = 1000 * 30 // 30 seconds in milliseconds async function fetchBlockHeight () { let blockHeight = 0 try { const height = await lndService.getHeight({ lnd }) blockHeight = height.current_block_height } catch (err) { console.error('fetchBlockHeight', err) } cache.set('block', { height: blockHeight, createdAt: Date.now() }) return blockHeight } async function getBlockHeight () { if (cache.has('block')) { const { height, createdAt } = cache.get('block') const expired = createdAt + expiresIn < Date.now() if (expired) fetchBlockHeight().catch(console.error) // update cache return height // serve stale block height (this on the SSR critical path) } else { fetchBlockHeight().catch(console.error) } return 0 } export default { Query: { blockHeight: async (parent, opts, ctx) => { return await getBlockHeight() } } }