function createInfuraMiddleware(opts = {}) {
const network = opts.network || 'mainnet'
const maxAttempts = opts.maxAttempts || 5
// validate options
if (!maxAttempts) throw new Error(`Invalid value for 'maxAttempts': "${maxAttempts}" (${typeof maxAttempts})`)
return createAsyncMiddleware(async (req, res, next) => {
// retry MAX_ATTEMPTS times, if error matches filter
for (let attempt = 1; attempt <= maxAttempts; attempt++) {
try {
// attempt request
await performFetch(network, req, res)
// request was succesful
break
} catch (err) {
// an error was caught while performing the request
// if not retriable, resolve with the encountered error
if (!isRetriableError(err)) {
// abort with error
throw err
}
// if no more attempts remaining, throw an error
const remainingAttempts = maxAttempts - attempt
if (!remainingAttempts) {
const errMsg = `InfuraProvider - cannot complete request. All retries exhausted.\nOriginal Error:\n${err.toString()}\n\n`
const retriesExhaustedErr = new Error(errMsg)
throw retriesExhaustedErr
}
// otherwise, ignore error and retry again after timeout
await timeout(1000)
}
}
// request was handled correctly, end
})
}
function createInfuraMiddleware({
network = 'mainnet'
}) {
return createAsyncMiddleware(async (req, res) => {
const {
fetchUrl,
fetchParams
} = fetchConfigFromReq({
network,
req
})
const response = await fetch(fetchUrl, fetchParams)
const rawData = await response.text()
// handle errors
if (!response.ok) {
switch (response.status) {
case 405: {
throw new JsonRpcError.MethodNotFound()
}
case 418: {
const msg = 'Request is being rate limited.'
const error = new Error(msg)
throw new JsonRpcError.InternalError(error)
}
case 503:
case 504: {
const msg = 'Gateway timeout. The request took too long to process.'
const error = new Error(msg)
throw new JsonRpcError.InternalError(error)
}
default: {
const error = new Error(rawData)
throw new JsonRpcError.InternalError(error)
}
}
}
// special case for now
if (req.method === 'eth_getBlockByNumber' && rawData === 'Not Found') {
res.result = null
return
}
const data = JSON.parse(rawData)
res.result = data.result
res.error = data.error
})
}