Resolution

• The following code calculates failure score

    183 /*
    184  * This function is designed to serve a fairly specific purpose.
    185  * Occasionally our vBNS-connected caches can talk to each other, but not
    186  * the rest of the world.  Here we try to detect frequent failures which
    187  * make the cache unusable (e.g. DNS lookup and connect() failures).  If
    188  * the failure:success ratio goes above 1.0 then we go into "hit only"
    189  * mode where we only return UDP_HIT or UDP_MISS_NOFETCH.  Neighbors
    190  * will only fetch HITs from us if they are using the ICP protocol.  We
    191  * stay in this mode for 5 minutes.
    192  *
    193  * Duane W., Sept 16, 1996
    194  */
    195 
:
    198 static void
    199 checkFailureRatio(err_type etype, hier_code hcode)
    200 {
    201     static double magic_factor = 100.0;
    202     double n_good;
    203     double n_bad;
    204 
    205     if (hcode == HIER_NONE)
    206         return;
    207 
    208     n_good = magic_factor / (1.0 + request_failure_ratio);
    209 
    210     n_bad = magic_factor - n_good;
    211 
    212     switch (etype) {
    213 
    214     case ERR_DNS_FAIL:
    215 
    216     case ERR_CONNECT_FAIL:
    217     case ERR_SECURE_CONNECT_FAIL:
    218 
    219     case ERR_READ_ERROR:
    220         n_bad++;
    221         break;
    222 
    223     default:
    224         n_good++;
    225     }
    226 
    227     request_failure_ratio = n_bad / n_good;
    228 
    229     if (hit_only_mode_until > squid_curtime)
    230         return;
    231 
    232     if (request_failure_ratio < 1.0)
    233         return;
    234 
    235     debugs(33, 0, "Failure Ratio at "<< std::setw(4)<<
    236            std::setprecision(3) << request_failure_ratio);
    237 
    238     debugs(33, 0, "Going into hit-only-mode for " <<
    239            FAILURE_MODE_TIME / 60 << " minutes...");
    240 
    241     hit_only_mode_until = squid_curtime + FAILURE_MODE_TIME;
    242 
    243     request_failure_ratio = 0.8;        /* reset to something less than 1.0 */
    244 }

    246 ClientHttpRequest::~ClientHttpRequest()
    247 {
    248     debugs(33, 3, "httpRequestFree: " << uri);
    249     PROF_start(httpRequestFree);
    250 
    251     // Even though freeResources() below may destroy the request,
    252     // we no longer set request->body_pipe to NULL here
    253     // because we did not initiate that pipe (ConnStateData did)
    254 
    255     /* the ICP check here was erroneous
    256      * - StoreEntry::releaseRequest was always called if entry was valid
    257      */
    258     assert(logType < LOG_TYPE_MAX);
    259 
    260     logRequest();
    261 
    262     loggingEntry(NULL);
    263 
    264     if (request)
    265         checkFailureRatio(request->errType, al.hier.code);
    266 
    267     freeResources();
    268 
    269 #if USE_ADAPTATION
    270     announceInitiatorAbort(virginHeadSource);
    271 
    272     if (adaptedBodySource != NULL)
    273         stopConsumingFrom(adaptedBodySource);
    274 #endif
    275 
    276     if (calloutContext)
    277         delete calloutContext;
    278 
    279     if (conn_)
    280         cbdataReferenceDone(conn_);
    281 
    282     /* moving to the next connection is handled by the context free */
    283     dlinkDelete(&active, &ClientActiveRequests);
    284 
    285     PROF_stop(httpRequestFree);
    286 }