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I have inherited a server with some performance issues. It is running node js, nginx, basic MEAN stack. (DB on another server though)

Whenever I copied a file (log file with size of around 150MB) or vim a file with that size, the output of "iostat -x 1" will be like below

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
scd0              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda               0.00  8137.62    0.00   49.50     0.00 29924.75   604.48    17.32  123.54  16.50  81.68

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.59    0.00   24.34    0.00    0.00   74.07

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
scd0              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda               0.00     0.00    0.00   39.39     0.00 36606.06   929.23     2.42  351.64   1.87   7.37

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           2.78    0.00   24.44    0.00    0.00   72.78

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
scd0              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00

The main reason I am bringing this up is because sometimes a simple RESTFUL API that my nodejs is serving will respond slowly (from 10ms to 500ms) and I am not sure what to look for or check what is causing this.

The same codebase copied to another server will run smoothly without issues, the problem mentioned above is the only lead I can find that there might be something wrong with the server but I am not sure what is it.

The codes are like below:

In one file statistic/index.js:

var tracker = function (data) {
  piwik.tracker(data);
};

exports.tracker = tracker;

In another file statistic/piwik.js:

exports.tracker = function (data) {
  var params = {};

  /** Assign params with data - just static string **/

  /** API_URL is another machine in same LAN **/
  needle.post(API_URL, params, function (err, response, body) {
    if (err || (response.statusCode !== 200 && response.statusCode !== 204)) {
      util.error(err);
    }
  });
};

In the file that is calling the above route/getuser.js:

exports.getUser = function (req, res) {

  async.auto({
    get_user: function (cb) {
      /** Read user data from DB **/
      cb();
    },
    record_statistic: ['get_user', function (cb) {
      statistic.tracker({ /** Pass static string data **/});
      cb();
    }]
  }, function (err) {
    if (err) {
      res.json(err);
    } else {
      res.json();
    }
  });
};

The reason I am mentioning the above codes is because when I remarked out statistic.tracker({ /** Pass static string data **/}); The function will response within 50ms, but if I include it most of the time it will respond between 100ms - 500ms. I have even put a timestamp check for the "needle" HTTP post, and it respond within 10 - 20ms.

When I copy a file (cp -p x.txt y.txt) especially when it is a > 100MB file, it will also slow down my node js. But even when I am not doing anything on the server besides nginx and node js listening for request the codes below will respond slowly. (If I didn't remark out the code)

I am suspecting IO but where else to check? or what to look out for?

Below are some info about the server:

[ec2-user@tlp-backend logs]$ uname -a
Linux tlp-backend 2.6.32-71.el6.x86_64 #1 SMP Fri May 20 03:51:51 BST 2011 x86_64 x86_64 x86_64 GNU/Linux

[ec2-user@tlp-backend logs]$ cat /proc/scsi/scsi 
Attached devices:
Host: scsi1 Channel: 00 Id: 00 Lun: 00
  Vendor: NECVMWar Model: VMware IDE CDR10 Rev: 1.00
  Type:   CD-ROM                           ANSI  SCSI revision: 05
Host: scsi2 Channel: 00 Id: 00 Lun: 00
  Vendor: VMware,  Model: VMware Virtual S Rev: 1.0 
  Type:   Direct-Access                    ANSI  SCSI revision: 02
[ec2-user@tlp-backend logs]$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 30502
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 1024
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

[ec2-user@tlp-backend logs]$ more /proc/meminfo 
MemTotal:        3918960 kB
MemFree:          392260 kB
Buffers:          296116 kB
Cached:          1205652 kB
SwapCached:          364 kB
Active:          1725084 kB
Inactive:        1155564 kB
Active(anon):     949492 kB
Inactive(anon):   430528 kB
Active(file):     775592 kB
Inactive(file):   725036 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       4095992 kB
SwapFree:        4092872 kB
Dirty:                28 kB
Writeback:             0 kB
AnonPages:       1378528 kB
Mapped:            29860 kB
Shmem:              1140 kB
Slab:             588628 kB
SReclaimable:     461108 kB
SUnreclaim:       127520 kB
KernelStack:        2296 kB
PageTables:        16940 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     6055472 kB
Committed_AS:    1829320 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      288456 kB
VmallocChunk:   34359446140 kB
HardwareCorrupted:     0 kB
AnonHugePages:    507904 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       10240 kB
DirectMap2M:     4184064 kB

[ec2-user@tlp-backend logs]$ more /proc/cpuinfo 
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 44
model name  : Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz
stepping    : 2
cpu MHz     : 2400.000
cache size  : 12288 KB
physical id : 0
siblings    : 2
core id     : 0
cpu cores   : 2
apicid      : 0
initial apicid  : 0
fpu     : yes
fpu_exception   : yes
cpuid level : 11
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat 
pse36 clflush dts mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc arch
_perfmon pebs bts rep_good xtopology tsc_reliable nonstop_tsc aperfmperf unfair_
spinlock pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 x2apic popcnt aes hypervisor lah
f_lm ida arat
bogomips    : 4800.00
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

processor   : 1
vendor_id   : GenuineIntel
cpu family  : 6
model       : 44
model name  : Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz
stepping    : 2
cpu MHz     : 2400.000
cache size  : 12288 KB
physical id : 0
siblings    : 2
core id     : 1
cpu cores   : 2
apicid      : 1
initial apicid  : 1
fpu     : yes
fpu_exception   : yes
cpuid level : 11
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat 
pse36 clflush dts mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc arch
_perfmon pebs bts rep_good xtopology tsc_reliable nonstop_tsc aperfmperf unfair_
spinlock pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 x2apic popcnt aes hypervisor lah
f_lm ida arat
bogomips    : 4800.00
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

processor   : 2
vendor_id   : GenuineIntel
cpu family  : 6
model       : 44
model name  : Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz
stepping    : 2
cpu MHz     : 2400.000
cache size  : 12288 KB
physical id : 1
siblings    : 2
core id     : 0
cpu cores   : 2
apicid      : 2
initial apicid  : 2
fpu     : yes
fpu_exception   : yes
cpuid level : 11
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat 
pse36 clflush dts mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc arch
_perfmon pebs bts rep_good xtopology tsc_reliable nonstop_tsc aperfmperf unfair_
spinlock pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 x2apic popcnt aes hypervisor lah
f_lm ida arat
bogomips    : 4800.00
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

processor   : 3
vendor_id   : GenuineIntel
cpu family  : 6
model       : 44
model name  : Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz
stepping    : 2
cpu MHz     : 2400.000
cache size  : 12288 KB
physical id : 1
siblings    : 2
core id     : 1
cpu cores   : 2
apicid      : 3
initial apicid  : 3
fpu     : yes
fpu_exception   : yes
cpuid level : 11
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat 
pse36 clflush dts mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc arch
_perfmon pebs bts rep_good xtopology tsc_reliable nonstop_tsc aperfmperf unfair_
spinlock pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 x2apic popcnt aes hypervisor lah
f_lm ida arat
bogomips    : 4800.00
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

 top - 18:02:58 up 26 days, 18:49,  2 users,  load average: 0.00, 0.00, 0.00
Tasks: 176 total,   1 running, 175 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.1%sy,  0.0%ni, 99.9%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   3918960k total,  3522368k used,   396592k free,   295340k buffers
Swap:  4095992k total,     3120k used,  4092872k free,  1201660k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND           
    1 root      20   0 19340 1248 1040 S  0.0  0.0   0:03.45 init               
    2 root      20   0     0    0    0 S  0.0  0.0   0:00.01 kthreadd           
    3 root      RT   0     0    0    0 S  0.0  0.0   0:02.55 migration/0        
    4 root      20   0     0    0    0 S  0.0  0.0   0:01.57 ksoftirqd/0        
    5 root      RT   0     0    0    0 S  0.0  0.0   0:00.00 watchdog/0         
    6 root      RT   0     0    0    0 S  0.0  0.0   0:18.87 migration/1        
    7 root      20   0     0    0    0 S  0.0  0.0   0:01.34 ksoftirqd/1        
    8 root      RT   0     0    0    0 S  0.0  0.0   0:00.00 watchdog/1         
    9 root      RT   0     0    0    0 S  0.0  0.0   0:01.90 migration/2        
   10 root      20   0     0    0    0 S  0.0  0.0   0:01.30 ksoftirqd/2        
   11 root      RT   0     0    0    0 S  0.0  0.0   0:00.00 watchdog/2  
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Apparently, the main problem is coming from the code itself. When you are mixing async.auto with needle package, you need to explicitly stating { connection: 'keep-alive' } in HTTP header

See more info here: https://github.com/tomas/needle/issues/148

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