Linux – Cannot assign requested address
While running a performance test on a local web service, I encountered below error –
$ ab -n 600000 -c 10000 http://localhost:8080/test
...
Benchmarking localhost (be patient)
Test aborted after 10 failures
apr_socket_connect(): Cannot assign requested address (99)
Clearly the number of concurrent requests(-n) and concurrent connections(-c) is high. But would it be possible to tweak my system so that it can handle this? Apparently yes. Doing some reading no Ephemeral port range. For a typical TCP connection, a 4-tuple of source IP/port and destination IP/port is required. In our case, the source and destination IP is fixed (127.0.0.1) as well as the destination port (8080). How many source port range do we have?
$ cat /proc/sys/net/ipv4/ip_local_port_range
32768 60999
$ echo $((60999-32768))
28231
By increasing this port range, the system will accept more concurrent connections. Run below command under root –
root@lindell:~# echo "16000 65535" > /proc/sys/net/ipv4/ip_local_port_range
root@lindell:~# cat /proc/sys/net/ipv4/ip_local_port_range
16000 65535
The performance test now runs successfully –
$ ab -n 600000 -c 10000 http://localhost:8080/test
This is ApacheBench, Version 2.3 <$Revision: 1706008 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking localhost (be patient)
Completed 60000 requests
Completed 120000 requests
Completed 180000 requests
Completed 240000 requests
Completed 300000 requests
Completed 360000 requests
Completed 420000 requests
Completed 480000 requests
Completed 540000 requests
Completed 600000 requests
Finished 600000 requests
Server Software:
Server Hostname: localhost
Server Port: 8080
Document Path: /test
Document Length: 13 bytes
Concurrency Level: 10000
Time taken for tests: 122.307 seconds
Complete requests: 600000
Failed requests: 0
Total transferred: 78000000 bytes
HTML transferred: 7800000 bytes
Requests per second: 4905.69 [#/sec] (mean)
Time per request: 2038.449 [ms] (mean)
Time per request: 0.204 [ms] (mean, across all concurrent requests)
Transfer rate: 622.79 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 308 848 180.0 833 3955
Processing: 293 1175 198.5 1190 1967
Waiting: 88 882 210.3 946 1738
Total: 932 2023 208.9 2018 5146
Percentage of the requests served within a certain time (ms)
50% 2018
66% 2085
75% 2115
80% 2138
90% 2216
95% 2298
98% 2411
99% 2961
100% 5146 (longest request)
$ netstat -talpn |grep '127.0.0.1:8080' |wc -l
34241
