Understanding Chrome network log Stalled state

Question

I ve a following network log in chrome     I don t understand one thing in it  what s the difference between filled gray bars and transparent gray bars

User · Answer

https   developers google com web tools chrome-devtools network-performance understanding-resource-timing  This comes from the official site of Chome-devtools and it helps  Here i quote          Queuing   If a request is queued it indicated that          The request was postponed by the rendering engine because it s considered lower priority than critical resources  such as scripts styles   This often happens with images    The request was put on hold to wait for an unavailable TCP socket that s about to free up    The request was put on hold because the browser only allows six TCP connections per origin on HTTP 1    Time spent making disk cache entries  typically very quick        Stalled Blocking   Time the request spent waiting before it could be sent  It can be waiting for any of the reasons described for Queueing  Additionally  this time is inclusive of any time spent in proxy negotiation

User · Answer

DevTools   network  explain empty bars preceeding request     Investigated further and have identified that there s no significant difference between our Stalled and Queueing ranges  Both   are calculated from the delta s of other timestamps  rather than   provided from netstack or renderer             Currently  if we re waiting for a socket to become available          we ll call it stalled if some proxy negotiation happened   we ll call it queuing if no proxy ssl work was required

User · Answer

Google gives a breakdown of these fields in the Evaluating network performance section of their DevTools documentation  Excerpt from Resource network timing   Stalled Blocking Time the request spent waiting before it could be sent  This time is inclusive of any time spent in proxy negotiation  Additionally  this time will include when the browser is waiting for an already established connection to become available for re-use  obeying Chrome s maximum six TCP connection per origin rule    If you forget  Chrome has an  quot Explanation quot  link in the hover tooltip and under the  quot Timing quot  panel   Basically  the primary reason you will see this is because Chrome will only download 6 files per-server at a time and other requests will be stalled until a connection slot becomes available  This isn t necessarily something that needs fixing  but one way to avoid the stalled state would be to distribute the files across multiple domain names and or servers  keeping CORS in mind if applicable to your needs  however HTTP2 is probably a better option going forward  Resource bundling  like JS and CSS concatenation  can also help to reduce amount of stalled connections

User · Answer

My case is the page is sending multiple requests with different parameters when  it was open  So most are being  stalled   Following requests immediately sent gets  stalled   Avoiding unnecessary requests would be better  to be lazy

User · Answer

Since many people arrive here debugging their slow website I would like to inform you about my case which none of the google explanations helped to resolve  My huge stalled times  sometimes 1min  were caused by Apache running on Windows having too few worker threads to handle the connections  therefore they were being queued   This may apply to you if you apache log has following note   Server ran out of threads to serve requests  Consider raising the ThreadsPerChild setting   This issue is resolved in Apache httpd conf  Uncomment   Include conf extra httpd-mpm conf  And edit httpd-mpm conf    lt IfModule mpm winnt module gt     ThreadLimit              2000    ThreadsPerChild          2000    MaxConnectionsPerChild   0  lt  IfModule gt    Note that you may not need 2000 threads  or may need more  2000 was OK for my case

[google-chrome] Understanding Chrome network log "Stalled" state

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