defaultClientErrorHandler() — fastify Function Reference

Architecture documentation for the defaultClientErrorHandler() function in fastify.js from the fastify codebase.

Function javascript CoreKernel InstanceFactory

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CoreKernel→ InstanceFactory→ defaultClientErrorHandler() — fastify Function Reference

Dependency Diagram

graph TD
  b7187f8b_e1ca_c935_a50a_ce22faef4f11["defaultClientErrorHandler()"]
  2bf9986b_b7fb_0c78_f075_72fbe6f4672b["fastify.js"]
  b7187f8b_e1ca_c935_a50a_ce22faef4f11 -->|defined in| 2bf9986b_b7fb_0c78_f075_72fbe6f4672b
  style b7187f8b_e1ca_c935_a50a_ce22faef4f11 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

fastify.js lines 921–959

function defaultClientErrorHandler (err, socket) {
  // In case of a connection reset, the socket has been destroyed and there is nothing that needs to be done.
  // https://nodejs.org/api/http.html#http_event_clienterror
  if (err.code === 'ECONNRESET' || socket.destroyed) {
    return
  }

  let body, errorCode, errorStatus, errorLabel

  if (err.code === 'ERR_HTTP_REQUEST_TIMEOUT') {
    errorCode = '408'
    errorStatus = http.STATUS_CODES[errorCode]
    body = `{"error":"${errorStatus}","message":"Client Timeout","statusCode":408}`
    errorLabel = 'timeout'
  } else if (err.code === 'HPE_HEADER_OVERFLOW') {
    errorCode = '431'
    errorStatus = http.STATUS_CODES[errorCode]
    body = `{"error":"${errorStatus}","message":"Exceeded maximum allowed HTTP header size","statusCode":431}`
    errorLabel = 'header_overflow'
  } else {
    errorCode = '400'
    errorStatus = http.STATUS_CODES[errorCode]
    body = `{"error":"${errorStatus}","message":"Client Error","statusCode":400}`
    errorLabel = 'error'
  }

  // Most devs do not know what to do with this error.
  // In the vast majority of cases, it's a network error and/or some
  // config issue on the load balancer side.
  this.log.trace({ err }, `client ${errorLabel}`)
  // Copying standard node behavior
  // https://github.com/nodejs/node/blob/6ca23d7846cb47e84fd344543e394e50938540be/lib/_http_server.js#L666

  // If the socket is not writable, there is no reason to try to send data.
  if (socket.writable) {
    socket.write(`HTTP/1.1 ${errorCode} ${errorStatus}\r\nContent-Length: ${body.length}\r\nContent-Type: application/json\r\n\r\n${body}`)
  }
  socket.destroy(err)
}