apache traffic server interpret via header，how to decode this code by myself - apache-traffic-server

Question

{ server: 'ATS/5.0.1',
date: 'Thu, 04 Sep 2014 05:34:16 GMT',
'content-type': 'image/jpeg',
'content-length': '47265',
'last-modified': 'Sat, 09 Aug 2014 07:32:06 GMT',
expires: 'Mon, 25 Aug 2014 06:45:37 GMT',
'cache-control': 'max-age=604800',
'load-balancing': 'web39',
'x-cache-status': 'HIT',
'accept-ranges': 'bytes',
age: '94784',
connection: 'keep-alive',
via: 'http/1.1 upyun (ApacheTrafficServer/5.0.1 [cHs f ])'
}
The ATS protocol-encoded field ("cHs f") can be decoded at http://trafficserver.apache.org/tools/via
What should be done to decode it locally, on my server?
Is there any description of the encode-protocol?
Having the encode-protocol definition, I can decode it myself.

Answer 1

var codes = {}
codes[1] = {}
codes[1]['title'] = "client-info Request headers received from client. Value is one of:"
codes[1]['I'] = "If Modified Since (IMS)"
codes[1]['C'] = "cookie"
codes[1]['E'] = "error in request"
codes[1]['S'] = "simple request (not conditional)"
codes[1]['N'] = "no-cache"
codes[2] = {}
codes[2]['title'] = "cache-lookup Result of Traffic Server cache lookup for URL. Value is one of:"
codes[2]['A'] = "in cache, not acceptable (a cache \"MISS\")"
codes[2]['H'] = "in cache, fresh (a cache \"HIT\")"
codes[2]['S'] = "in cache, stale (a cache \"MISS\")"
codes[2]['R'] = "in cache, fresh Ram hit (a cache \"HIT\")"
codes[2]['M'] = "miss (a cache \"MISS\")"
codes[2][' '] = "no cache lookup performed"
codes[3] = {}
codes[3]['title'] = "server-info Response information received from origin server. Value is one of:"
codes[3]['E'] = "error in response"
codes[3][' '] = "no server connection needed"
codes[3]['S'] = "served"
codes[3]['N'] = "not-modified"
codes[4] = {}
codes[4]['title'] = "cache-fill Result of document write to cache. Value is one of:"
codes[4]['U'] = "updated old cache copy"
codes[4]['D'] = "cached copy deleted"
codes[4]['W'] = "written into cache (new copy)"
codes[4][' '] = "no cache write performed"
codes[5] = {}
codes[5]['title'] = "proxy-info Proxy operation result. Value is one of:"
codes[5]['R'] = "origin server revalidated"
codes[5][' '] = "unknown?"
codes[5]['S'] = "served"
codes[5]['N'] = "not-modified"
codes[6] = {}
codes[6]['title'] = "error-codes Value is one of:"
codes[6]['A'] = "authorization failure"
codes[6]['H'] = "header syntax unacceptable"
codes[6]['C'] = "connection to server failed"
codes[6]['T'] = "connection timed out"
codes[6]['S'] = "server related error"
codes[6]['D'] = "dns failure"
codes[6]['N'] = "no error"
codes[6]['F'] = "request forbidden"
codes[7] = {}
codes[7]['title'] = "tunnel-info Proxy-only service operation. Value is one of:"
codes[7][' '] = "no tunneling"
codes[7]['U'] = "tunneling because of url (url suggests dynamic content)"
codes[7]['M'] = "tunneling due to a method (e.g. CONNECT)"
codes[7]['O'] = "tunneling because cache is turned off"
codes[7]['F'] = "tunneling due to a header field (such as presence of If-Range header)"
codes[8] = {}
codes[8]['title'] = "cache-type and cache-lookup cache result values (2 characters)"
codes[8]['I'] = "icp"
codes[8][' '] = "cache miss or no cache lookup"
codes[8]['C'] = "cache"
codes[9] = {}
codes[9]['title'] = "cache-lookup-result character value is one of:"
codes[9][' '] = "no cache lookup"
codes[9]['S'] = "cache hit, but expired"
codes[9]['U'] = "cache hit, but client forces revalidate (e.g. Pragma: no-cache)"
codes[9]['D'] = "cache hit, but method forces revalidated (e.g. ftp, not anonymous)"
codes[9]['I'] = "conditional miss (client sent conditional, fresh in cache, returned 412)"
codes[9]['H'] = "cache hit"
codes[9]['M'] = "cache miss (url not in cache)"
codes[9]['C'] = "cache hit, but config forces revalidate"
codes[9]['N'] = "conditional hit (client sent conditional, doc fresh in cache, returned 304)"
codes[10] = {}
codes[10]['title'] = "icp-conn-info ICP status"
codes[10][' '] = "no icp"
codes[10]['S'] = "connection opened successfully"
codes[10]['F'] = "connection open failed"
codes[11] = {}
codes[11]['title'] = "parent-proxy parent proxy connection status"
codes[11][' '] = "no parent proxy"
codes[11]['S'] = "connection opened successfully"
codes[11]['F'] = "connection open failed"
codes[12] = {}
codes[12]['title'] = "server-conn-info origin server connection status"
codes[12][' '] = "no server connection"
codes[12]['S'] = "connection opened successfully"
codes[12]['F'] = "connection open failed"
function showVia(form, value) {
var text = value? value : form.via.value;
if (value) {
document.getElementById("via").value = value;
}
var via = document.getElementById("viaoutput")
var output = "";
var txtonly = text.match(/([a-zA-Z: ]+)/);
text = txtonly[1];
if (text.length == 5) {
text = text + " "
}
if (text.length == 24) {
var arr = text.match(/([a-zA-Z ]+):([a-zA-Z ]+)/);
output = output + "<h3>Proxy request results:</h3>";
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Request headers received from client:</div> <font color="#003399">' + codes[1][arr[1][1]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Result of Traffic Server cache lookup for URL:</div> <font color="#003399">' + codes[2][arr[1][3]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Response information received from origin server:</div> <font color="#003399">' + codes[3][arr[1][5]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Result of document write-to-cache:</div> <font color="#003399">' + codes[4][arr[1][7]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Proxy operation result:</div> <font color="#003399">' + codes[5][arr[1][9]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Error codes (if any):</div> <font color="#003399">' + codes[6][arr[1][11]] + '</font><br/>';
output = output + "<h3>Operational results:</h3>";
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Tunnel info:</div> <font color="#003399">' + codes[7][arr[2][1]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Cache-type and cache-lookup cache result values:</div> <font color="#003399">' + codes[8][arr[2][3]] + " / " + codes[9][arr[2][4]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">ICP status:</div> <font color="#003399">' + codes[10][arr[2][6]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Parent proxy connection status:</div> <font color="#003399">' + codes[11][arr[2][8]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Origin server connection status:</div> <font color="#003399">' + codes[12][arr[2][10]] + '</font><br/>';
} else if (text.length == 6) {
output = output + "<h3>Proxy request results:</h3>";
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Result of Traffic Server cache lookup for URL:</div> <font color="#003399">' + codes[2][text[1]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Response information received from origin server:</div> <font color="#003399">' + codes[3][text[3]] + '</font><br/>';
output = output + '<div style="width: 450px; font-weight: bold; float: left;">Result of document write-to-cache:</div> <font color="#003399">' + codes[4][text[5]] + '</font><br/>';
} else {
output = "Invalid VIA data, must be 24 or 6 characters long.";
}
via.innerHTML = output;
if (form) {
window.location.hash = escape(text);
}
return false;
}
function checkQuery() {
var url = location.href;
if (url.indexOf("#") > 0) {
var qs = url.substring(url.indexOf("#")+1).replace("%20", " ").replace("+", " ");
if (qs && qs.length > 5) {
showVia(false, qs);
}
}
}

Answer 2

As of v5.3.0 (I think), there's a new command line utility, traffic_via, which decodes this header. E.g.
% traffic_via '[cHs f ]'
Via header is [cHs f ], Length is 8
Via Header Details:
Result of Traffic Server cache lookup for URL :in cache, fresh (a cache "HIT")
Response information received from origin server :no server connection needed
Result of document write-to-cache: :no cache write performed