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Phalcon 2.0: Segmentation fault, empty response

Randomly, a Phalcon 2.0 application returns empty response. After retrying, without changing any code or input, I get a response.

I have two subdomains on the same physical machine. The first subdomain is a frontend API, and the second is a backend API. The frontend calls the backend over HTTP (not HTTPS) using CURL. Approximately 2/3 of the calls come back empty. When I retry 2 or 3 times, I get a response. The problem is less pronounced when I access the backend directly, and more pronounced when I access the frontend and it in turn calls the backend before responding. Depending on which of the two subdomans failed, I get either an empty response from the frontend, or an error "Empty reply from server" when the internal call to the backend service comes back empty.

Cache-Control header set to no-cache, and curl option CURLOPT_FRESH_CONNECT set to true don't have any effect.

Apache error log shows the following when the error occurs:

[core:notice] [pid 7062] AH00052: child pid 7070 exit signal Segmentation fault (11)

7070 is the process of the currently executing request.

On several occasions, I also noticed the index.php being executed twice back-to-back.

My application works fine with Phalcon 1.3.4.

My configuration: Apache 2.4 and PHP 5.5.9 on Linux Mint 64-bit running in a VMWare virtual machine with 4 GB of memory and 4 CPU cores.

Thank you for your help.

-Stan

UPDATE: I don't believe it is any of these already reported issues:

https://github.com/phalcon/cphalcon/issues/10126

https://github.com/phalcon/cphalcon/issues/2269

If I retry, it would eventually work without me changing any code, settings, or input.



34.6k

Could you please post a script that allow us to reproduce the issue?



3.0k

Same problem here. how does one debug these problems?



3.0k

the problem disapper on server restart though



34.6k
in reply to Faiz Mohamed Haneef

Could you please post a script that allow us to reproduce the issue?

Same problem here. how does one debug these problems?



3.0k

Code available here https://bitbucket.org/faizmh/phalcontest Deployed here https://phalcontest.azurewebsites.net/

Phalcon Author Phalcon Team and contributors Version 2.0.7 Build Date Aug 17 2015 14:25:34 Powered by Zephir Version 0.7.1b

PHPINFO Compiler MSVC9 (Visual C++ 2008) Architecture x86 Zend Extension Build API220100525,NTS,VC9

issue not reproducible now. Please check the code. I will report back once I find the problem



34.6k
edited Sep '15

How do you know you're having a segmentation fault?, this concept does not exactly exist on Windows. Also, what steps do I have to follow to see the problem?



3.0k
edited Sep '15

sorry. I was referring to Approximately 2/3 of the calls come back empty. When I retry 2 or 3 times, I get a response. This was happening when I was on IIS/Windows. The response were blank and 200 OK.

  1. Home https://phalcontest.azurewebsites.net/
  2. Login
  3. Access Logged in resource

step 3 would give intermediate blank response. (although not happening now. I will wait for another 2 weeks to update you on the result)



3.0k

recevied the same blank response once again; and this gets worse once you are in production environment



3.0k

So how does one debug these problems, there is no error in php log. Its a shame to get handicapped and relying on a forum with limited help



34.6k

I followed your steps, it never gives me a blank page



3.0k

I just have fiddler sessions to back my claim. no php error logs. Andres, how can I debug? what should I enable? if you could skype or team viewer, I could just show them. the issue resolves on server restart



34.6k
edited Sep '15

Could you please run ab against your host?

ab -n 100 -c 3 https://phalcontest.azurewebsites.net/sec/test
This is ApacheBench, Version 2.3 <$Revision: 1663405 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, https://www.zeustech.net/
Licensed to The Apache Software Foundation, https://www.apache.org/

Benchmarking phalcontest.azurewebsites.net (be patient).....done

Server Software:        Microsoft-IIS/8.0
Server Hostname:        phalcontest.azurewebsites.net
Server Port:            80

Document Path:          /sec/test
Document Length:        156 bytes

Concurrency Level:      3
Time taken for tests:   19.754 seconds
Complete requests:      100
Failed requests:        0
Total transferred:      75700 bytes
HTML transferred:       15600 bytes
Requests per second:    5.06 [#/sec] (mean)
Time per request:       592.631 [ms] (mean)
Time per request:       197.544 [ms] (mean, across all concurrent requests)
Transfer rate:          3.74 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      281  282   4.1    282     322
Processing:   287  304  60.5    290     797
Waiting:      287  302  44.7    290     612
Total:        568  587  61.1    572    1083

Percentage of the requests served within a certain time (ms)
  50%    572
  66%    574
  75%    575
  80%    576
  90%    607
  95%    677
  98%    824
  99%   1083
 100%   1083 (longest request)


3.0k
edited Sep '15

Blank response once again.

C:\wamp\bin\apache\Apache2.4.4\bin>ab -n 100 -c 3 https://xxx.azurewebsites.net/
This is ApacheBench, Version 2.3 <$Revision: 1430300 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, https://www.zeustech.net/
Licensed to The Apache Software Foundation, https://www.apache.org/

Benchmarking xxx.azurewebsites.net (be patient).....done

Server Software:        Microsoft-IIS/8.0
Server Hostname:        xxx.azurewebsites.net
Server Port:            80

Document Path:          /
Document Length:        100617 bytes

Concurrency Level:      3
Time taken for tests:   64.737 seconds
Complete requests:      100
Failed requests:        0
Write errors:           0
Total transferred:      10102500 bytes
HTML transferred:       10061700 bytes
Requests per second:    1.54 [#/sec] (mean)
Time per request:       1942.101 [ms] (mean)
Time per request:       647.367 [ms] (mean, across all concurrent requests)
Transfer rate:          152.40 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:       64  465 990.3    100    3265
Processing:   485 1468 1274.4    782    4144
Waiting:       82  364 718.7    154    3269
Total:        582 1933 1512.6    921    6768

Percentage of the requests served within a certain time (ms)
  50%    921
  66%   3589
  75%   3756
  80%   3796
  90%   3929
  95%   3986
  98%   4524
  99%   6768
 100%   6768 (longest request)


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Failed requests: 0 Write errors: 0



3.0k

the ab test was after I restarted the servers. Mind you these are production servers and I have to restart them immediately

Also please note during failures, the responses are always 200 OK Content-Length: 0 Content-Type: text/html

eventhough these failed responses are supposed to return content with json content-type

How do I tracing? shall I introduce some tracing code into my php to troubleshoot? It seems I will face this problem again in 48hrs