timeout - Varnish stops waiting after 1 second -

this problem gonna make me crazy: varnish istance stops waiting backend response after 1 second. every first call page 503 backend

daemon configured way:

daemon_opts="-a :80 \          -t localhost:6082 \          -f /etc/varnish/default.vcl \          -s /etc/varnish/secret \          -p thread_pool_add_delay=2 \          -p thread_pools=4 \          -p thread_pool_min=200 \          -p thread_pool_max=4000 \          -p timeout_linger=50 \          -p connect_timeout=300 \          -p first_byte_timeout=300 \          -p between_bytes_timeout=300 \          -p send_timeout=900 \          -s malloc,3g" 

and vcl backend:

backend default {           # define 1 backend .host = "127.0.0.1";        # ip or hostname of backend .port = "8080";           # port apache or whatever listening .probe = {    .url = "/";    .timeout = 1s;    .interval = 1s;    .window = 10;    .threshold = 8;   }   .first_byte_timeout     = 60s;   # how long wait before receive first byte our backend?   .connect_timeout        = 60s;     # how long wait backend connection?   .between_bytes_timeout  = 60s;     # how long wait between bytes received our backend? } 

here 1 call in log:

*   << request  >> 3440734    -   begin          req 3440733 rxreq -   timestamp      start: 1462781837.623325 0.000000 0.000000 -   timestamp      req: 1462781837.623325 0.000000 0.000000 -   reqstart       10.20.129.118 58572 -   reqmethod      -   requrl         xxxxx.html -   reqprotocol    http/1.1 -   reqheader      accept: image/jpeg, application/x-ms-application, image/gif, application/xaml+xml, image/pjpeg, application/x-ms-xbap, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, image/pjpeg, application/x-shockwave-flash, */* -   reqheader      referer: http://xxxxxx.html -   reqheader      accept-language: it-it -   reqheader      user-agent: mozilla/4.0 (compatible; msie 7.0; windows nt 6.1; trident/7.0; slcc2; .net clr 2.0.50727; .net clr 3.5.30729; .net clr 3.0.30729; media center pc 6.0; .net4.0c; .net4.0e) -   reqheader      accept-encoding: gzip, deflate -   reqheader      host: xxxxxx -   reqheader      dnt: 1 -   reqheader      connection: keep-alive -   reqheader      cookie: fc_uid=p; __utma=127650066.830977012.1423064118.1426582505.1426588086.20; _ga=ga1.3.830977012.1423064118; _gat_ua-13041322-1=1; znpcq003-38303300=71a0f671; ff607e18ab6c715f4bb35b5bbcbe1c56=d82989olp2v0ur3gpl2ouprko6; _ga=ga1.2.830977012.142306411 -   reqheader      x-forwarded-for: 10.20.129.118 -   vcl_call       recv -   requnset       host: xxx -   reqheader      host: xxx -   requrl         /xxxx.html -   requnset       cookie: fc_uid=p; __utma=127650066.830977012.1423064118.1426582505.1426588086.20; _ga=ga1.3.830977012.1423064118; _gat_ua-13041322-1=1; znpcq003-38303300=71a0f671; ff607e18ab6c715f4bb35b5bbcbe1c56=d82989olp2v0ur3gpl2ouprko6; _ga=ga1.2.830977012.142306411 -   reqheader      cookie: fc_uid=p; __utma=127650066.830977012.1423064118.1426582505.1426588086.20; _ga=ga1.3.830977012.1423064118; _gat_ua-13041322-1=1; znpcq003-38303300=71a0f671; ff607e18ab6c715f4bb35b5bbcbe1c56=d82989olp2v0ur3gpl2ouprko6; _ga=ga1.2.830977012.142306411 -   requnset       cookie: fc_uid=p; __utma=127650066.830977012.1423064118.1426582505.1426588086.20; _ga=ga1.3.830977012.1423064118; _gat_ua-13041322-1=1; znpcq003-38303300=71a0f671; ff607e18ab6c715f4bb35b5bbcbe1c56=d82989olp2v0ur3gpl2ouprko6; _ga=ga1.2.830977012.142306411 -   reqheader      cookie: fc_uid=p; __utma=127650066.830977012.1423064118.1426582505.1426588086.20; _ga=ga1.3.830977012.1423064118; _gat_ua-13041322-1=1; znpcq003-38303300=71a0f671; ff607e18ab6c715f4bb35b5bbcbe1c56=d82989olp2v0ur3gpl2ouprko6; _ga=ga1.2.830977012.142306411 -   reqheader      surrogate-capability: key=esi/1.0 -   vcl_return     hash -   requnset       accept-encoding: gzip, deflate -   reqheader      accept-encoding: gzip -   vcl_call       hash -   vcl_return     lookup -   vcl_call       miss -   vcl_return     fetch -   link           bereq 3440735 fetch -   timestamp      fetch: 1462781838.492085 0.868760 0.868760 -   timestamp      process: 1462781838.492101 0.868776 0.000016 -   respheader     date: mon, 09 may 2016 08:17:18 gmt -   respheader     server: varnish -   respheader     x-varnish: 3440734 -   respprotocol   http/1.1 -   respstatus     503 -   respreason     service unavailable -   respreason     service unavailable -   vcl_call       synth -   vcl_return     deliver -   respheader     content-length: 0 -   storage        malloc transient -   debug          "res_mode 2" -   respheader     connection: keep-alive -   timestamp      resp: 1462781838.492145 0.868820 0.000044 -   reqacct        985 0 985 153 0 153 -   end 

any precious help? suggestion?

pretty sure issue here:

.timeout = 1s; .interval = 1s; 

notice of them have time of 1s = 1 second. think what's happening backend's probe timeouts varnish flags "unhealthy" until backend respond in second or less.

try modifying values check whether thats issue or not