Understanding on 'Error to Origin (50x)' , 'Internal CDN Error (50x)' and 'External Error (50x)' in Chartron

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Overview

This document explains about definition of these values on OUI Chartron.

Definition of Error Types

• Error to Origin (50x) Hits/Sec
  • The hits per seconds of response 504. As RFC2616, "504" means "Gateway Timeout". But CS use this value for logging "Error to Origin".

  • The situation to return response 504 : If PX-503 response header starts with "O ", then log as 504.

    
• Internal CDN Error (50x) Hits/Sec
  • Definition : The hits per seconds of response 505. As RFC2616, "505" means "HTTP Version Not Supported". But CS use this value for logging "Internal CDN Error".

  • The situation to return response 505 : If PX-503 response header not starts with "O " , then log as 505.

    
• External Error (50x) Hits/Sec
  • Definition : The hits per seconds of response 50x received from origin.
  • If origin returns 504 or 505, CS logs as 503. (i.e. External Error = all of 5xx except 504,505)
• Internal timeout (202) 
  • Definition : The hits per seconds of response 202.
    The situation that a request has accepted, but internal timeout
    occurs. As RFC2616, "202" means "Accepted". CS use similary this
    meaning.
    • If a real 202 response come from origin, perhit log
      has other reponse headers like "Server" or "Date", etc. But 202 response
      without other headers, the situation is internal timeout.
    • While CS retries to other nodes, CS will disconnect client connection and log as 202. In this case, request client cannot receives any http response code nor headers.

Test environment

• Edge node : n5 (10.40.196.201)
• Shield node : n7 (10.40.196.203), n4(10.40.196.204)
• Origin : 10.40.198.222 (CustomHttpd)
• Attached file : very_small.mp4 (325117 bytes)
• Reproduce conditions
  • User -> CS edge
  • CS edge -> master or shield
  • CS shield -> origin
• 

Error Cases by connection state

• (CS Last level shield - origin)

  

  

  

• (CS node - CS node)

  

  

  

• Client - CS edge node

  

  

http.log messages