Sporadic long response times with upstream server
Igor A. Ippolitov
iippolitov at nginx.com
Thu Feb 21 10:05:01 UTC 2019
Assume, you have a really slow client.
Nginx will get upstream response in milliseconds and will start feeding
data to a client
In 3 seconds nginx completed the transfer and issues a log entry.
And you see what you see.
If this issue involves a single client - most likely it's a client issue
(possibly even a subnet issue)
If suddenly a whole bunch of different requests start getting long
request time - check your network load and connectivity
On 21.02.2019 3:57, joncard wrote:
> This is similar to a previous question, but my log data shows the opposite
> problem. I am seeing rare requests that take perhaps 3s or more, but typical
> response times are 100ms or less. This is the log entry for one of the
> problematic responses:
> LOAD_BALANCER_IP - - [20/Feb/2019:13:36:12 +0000] "POST /DevicePost
> HTTP/1.1" 200 16 "-" "-" "client-ip-redacted" 3.052 0.002 .
> Here is the log format:
> log_format timed_main '$remote_addr - $remote_user [$time_local] "$request"
> '$status $body_bytes_sent "$http_referer" '
> '"$http_user_agent" "$http_x_forwarded_for" '
> '$request_time $upstream_response_time $pipe';
> The 0.002 matches what the Node.js logs are reporting from the upstream
> server, and 3.052 matches what the Elastic Load Balancer is reporting as the
> response time is recorded. This was set up by AWS Elastic Beanstalk as the
> (mostly) default configuration for a Node.js application. The only changes
> were for this logging entry, and manually setting the Content-Type header
> (the client is an embedded device and their HTTP library doesn't include
> this header, which creates problems for Node.js Express).
> I think this indicates a delay in Node.js, but it is sporadic and I cannot
> tell if it is some kind of garbage collection, a caching problem (there
> should be no caching), or something else. Any help would be appreciated.
> (I'm sorry I don't know how to format the quotes. I can't find any
> instructions on what the admin called "quoting conventions typically used on
> mailing lists" in the post "Please Read Before Posting in this Forum").
> Posted at Nginx Forum: https://forum.nginx.org/read.php?2,283099,283099#msg-283099
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