PHP - curl_exec hangs

Question

I am having a strange problem with the below php function. Unfortunately this is one of those special "Production only" case.

function requestPost($url, $data)
{
        set_time_limit(60);
        $output = array();
        $curlSession = curl_init();

        if($curlSession == false)
                syslog(LOG_INFO,"Falied to create a curl sessions");

        // Set the URL
        curl_setopt ($curlSession, CURLOPT_URL, $url);
        // No headers, please
        curl_setopt ($curlSession, CURLOPT_HEADER, 0);
        // It's a POST request
        curl_setopt ($curlSession, CURLOPT_POST, 1);
        // Set the fields for the POST
        curl_setopt ($curlSession, CURLOPT_POSTFIELDS, $data);
        // Return it direct, don't print it out
        curl_setopt($curlSession, CURLOPT_RETURNTRANSFER,1);
        // This connection will timeout in 30 seconds
        curl_setopt($curlSession, CURLOPT_TIMEOUT,30);
        //The next two lines must be present for the kit to work with newer version of cURL
        //You should remove them if you have any problems in earlier versions of cURL
        curl_setopt($curlSession, CURLOPT_SSL_VERIFYPEER, FALSE);
        curl_setopt($curlSession, CURLOPT_SSL_VERIFYHOST, 1);

        //Send the request and store the result in an array
        syslog(LOG_INFO,"base.php::requestPost() :  BEFORE SENDING CURL ");

        $rawresponse = curl_exec($curlSession);

}

PHP 5.3.6 (cli) (built: Mar 17 2011 21:19:28) 
curl Version          : 7.20.1
NSS Version           : 3.12.9
apr Version           : 1.4.5
Php Version           : 5.3.6

This seems to hang at curl_exec randomly.I am not a php developer so i have no idea where to begin.

I have noticed that when the curl requests are "hung" , on stopping the httpd daemon it attempts to send out these requests, so it might appear they are getting buffered or stuck in the httpd server. Any pointers would be appreciated.

Edit: I managed to get the stack trace out of the web server.

(gdb) where
#0  0x00c15416 in __kernel_vsyscall ()
#1  0x002f522c in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0x00a73a9d in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libc.so.6
#3  0x00b9b869 in PR_WaitCondVar () from /lib/libnspr4.so
#4  0x00809c0f in NSSRWLock_LockWrite_Util () from /usr/lib/libnssutil3.so
#5  0x05e9ae0e in ?? () from /usr/lib/libnss3.so
#6  0x05ebd014 in ?? () from /usr/lib/libnss3.so
#7  0x05ebd60d in ?? () from /usr/lib/libnss3.so
#8  0x05eb0506 in SECMOD_LoadModule () from /usr/lib/libnss3.so
#9  0x05eb047f in SECMOD_LoadModule () from /usr/lib/libnss3.so
#10 0x05e7c007 in ?? () from /usr/lib/libnss3.so
#11 0x05e7c95e in NSS_Initialize () from /usr/lib/libnss3.so
#12 0x008e8609 in ?? () from /usr/lib/libcurl.so.4
#13 0x008e9215 in Curl_nss_connect () from /usr/lib/libcurl.so.4
#14 0x008df9a3 in Curl_ssl_connect () from /usr/lib/libcurl.so.4
#15 0x008bc1fa in Curl_http_connect () from /usr/lib/libcurl.so.4
#16 0x008c44c6 in Curl_protocol_connect () from /usr/lib/libcurl.so.4
#17 0x008c5075 in ?? () from /usr/lib/libcurl.so.4
#18 0x008c58cf in Curl_async_resolved () from /usr/lib/libcurl.so.4
#19 0x008d1b2f in Curl_perform () from /usr/lib/libcurl.so.4
#20 0x008d2a74 in curl_easy_perform () from /usr/lib/libcurl.so.4
#21 0x006b4693 in ?? () from /usr/lib/php/modules/curl.so
#22 0x056e4ac9 in ?? () from /etc/httpd/modules/libphp5.so
#23 0x056bb87e in execute () from /etc/httpd/modules/libphp5.so
#24 0x05693a66 in zend_execute_scripts () from /etc/httpd/modules/libphp5.so
#25 0x05639cb6 in php_execute_script () from /etc/httpd/modules/libphp5.so
#26 0x057236b3 in ?? () from /etc/httpd/modules/libphp5.so
#27 0x00dc6421 in ap_run_handler ()
#28 0x00dca166 in ap_invoke_handler ()
#29 0x00dd6fa8 in ap_process_request ()
#30 0x00dd39e8 in ?? ()
#31 0x00dcec71 in ap_run_process_connection ()
#32 0x00ddc44a in ?? ()
#33 0x00ddc7ee in ?? ()
#34 0x00ddd793 in ap_mpm_run ()
#35 0x00db0ab2 in main ()

It appears to be stuck in a pthread_condition wait state. Does any one have a clue ? The same request is successful every single time via the command line; so it does point towards the libraries.

Edit:

Following is the call it never comes out from.

* About to connect() to live.sagepay.com port 443 (#0)
*   Trying x.x.x.x... * connected
* Connected to live.sagepay.com (x.x.x.x) port 443 (#0)
* warning: ignoring unsupported value (1) of ssl.verifyhost
*   CAfile: /etc/pki/tls/certs/ca-bundle.crt
  CApath: none
* SSL connection using SSL_RSA_WITH_RC4_128_MD5
* Server certificate:
*       subject: CN=live.sagepay.com,OU="Member, VeriSign Trust Network",OU=Authenticated by VeriSign,OU=Terms of use at www.verisign.co.uk/rpa (c)05,OU=Sage,O=Sage (UK) Limited,L=Newcastle Upon Tyne,ST=TYNE AND WEAR,C=GB,serialNumber=x.x.x,OID.x.x.x=Private Organization,OID.x.x.x.x=GB
*       start date: Mar 05 00:00:00 2011 GMT
*       expire date: Mar 04 23:59:59 2013 GMT
*       common name: live.sagepay.com
*       issuer: CN=VeriSign Class 3 Extended Validation SSL SGC CA,OU=Terms of use at https://www.verisign.com/rpa (c)06,OU=VeriSign Trust Network,O="VeriSign, Inc.",C=US
> POST /gateway/service/vspserver-register.vsp HTTP/1.1^M
Host: live.sagepay.com^M
Accept: */*^M
Content-Length: 664^M
Content-Type: application/x-www-form-urlencoded^M
^M
< HTTP/1.1 200 OK^M
< Date: Wed, 15 Jun 2011 16:11:43 GMT^M
< Server: Microsoft-IIS/6.0^M
< X-Powered-By: ASP.NET^M
< Content-Language: en-GB^M
< Content-Length: 276^M
< Set-Cookie: NSC_wjq-tbhfqbz-dpn-ofx=xxxx;expires=Wed, 15-Jun-2011 16:48:26 GMT;path=/;secure;httponly^M
< ^M
* Connection #0 to host live.sagepay.com left intact

Edit: Problem was with NSS, recompiled curl with OpenSSL and a few more hoops for dependencies( libssh2) & it seems to be working fine so far.

Cheers!

What url are you connecting to? If you are accessing a dynamic page you may just be waiting for the remote server to create and serve the content. — ben, Commented Jun 10, 2011 at 15:59
it is pointing to an e-commerce vendor like paypal. it is a https link. — Ricko M, Commented Jun 10, 2011 at 16:01
How long does the process hang before you stop the daemon? You say it hangs randomly, do you mean for some urls it doesn't hang, or for some post data it doesn't hang? Or, given the same url and data, sometimes it hangs and sometimes it succeeds? — ben, Commented Jun 10, 2011 at 16:50
Hi ben, sorry about the delay in getting back. It hangs randomly for same data/url. The response if successful is instantaneous. — Ricko M, Commented Jun 13, 2011 at 8:25

Frederic Bazin · Accepted Answer · 2011-06-13 09:08:26Z

12

add the following at the end your script to get the cause of failure

if( $rawresponse === false )
    syslog( LOG_INFO , "base.php::requestPost() : ".curl_error($curlSession) );

EDIT 1

It could be an internal problem of curl. Before all check all server runtimes are up to date ( php, php-curl and apache at least). Check all their logs..... Then I would recommand comparing results between several production environment or a dev/test environment.

Finally try to narrow down a minimal testcase that could reproduce your issue and publish full code for the test case.

edited Jun 13, 2011 at 9:08

answered Jun 10, 2011 at 18:25

Frederic Bazin

1,52912 silver badges27 bronze badges

It unfortunately does not come out of the curl_exec call at all. Is there any way to debug the function itself ? Being production env ; i might be short on few options.
– Ricko M
Commented Jun 13, 2011 at 8:26
I am not aware of any method to debug internals of libcurl expect low level C debugging. See my update above. Also you can try network traces ( wireshark or tcpdump) but I doubt it would solve your issue.
– Frederic Bazin
Commented Jun 13, 2011 at 9:05
unfortunately , this is one of those "rare" on production env only. I have tried to bring ever single library i could think of in synch.
– Ricko M
Commented Jun 14, 2011 at 16:37

Add a comment |

Alix Axel · Accepted Answer · 2011-06-16 14:37:09Z

8

+25

The stack trace clearly shows that the break you did occur within the NSS crypto library that your libcurl is built to use for SSL.

libcurl has got a lot of NSS-related fixes since the libcurl version you use, and possibly you're not using the most up-to-date NSS either. I would strongly suggest that you consider upgrading to the latest and greatest before you pull all your hair out on this problem.

To debug this problem, I would recommend you try to repeat it with the curl command line from the same server, and make good use of the --trace-ascii command.

edited Jun 16, 2011 at 14:37

Alix Axel

154k99 gold badges399 silver badges504 bronze badges

answered Jun 15, 2011 at 21:10

Daniel Stenberg

57k18 gold badges156 silver badges229 bronze badges

Thanks for your reply. Unfortunately i have all the libraries updated for FC 13. I am in fact considering a downgrade :( The same request is successful via command line every single time, so it does point out to one of the dependent libraries.
– Ricko M
Commented Jun 16, 2011 at 9:37
1

I would rather say it points to something in the PHP environment as the command line tool uses the same libcurl and NSS libraries...
– Daniel Stenberg
Commented Jun 16, 2011 at 12:53
That's a vital piece of information. Cheers! will try to downgrade php & wrestle it.
– Ricko M
Commented Jun 16, 2011 at 14:51
Is there any implication of a line which is facing severe packet loss to cause an issue as such ? As i understand the higher layers should take care of re-transmission .. Cheers!
– Ricko M
Commented Jun 21, 2011 at 14:02

Add a comment |

Ricko M · Accepted Answer · 2011-06-29 09:55:38Z

6

The problem was NSS. I recompiled curl with OpenSSL and so far it has not shown any issues.

Cheers!

answered Jun 29, 2011 at 9:55

Ricko M

1,7845 gold badges24 silver badges44 bronze badges

Add a comment |

Ярослав Рахматуллин · Accepted Answer · 2011-06-21 14:59:36Z

2

Have you tried installing a different version of apache and php? Do you have them in the package manager? If not, try compiling the latest apache, php and curl manually and see if you get the same result.

answered Jun 21, 2011 at 14:59

Ярослав Рахматуллин

7,7791 gold badge42 silver badges62 bronze badges

That is what i plan to do as well , i tried a few repos which would allow me to safely downgrade, in case of httpd , the chain is way to deep to be played around with. Thanks!
– Ricko M
Commented Jun 21, 2011 at 15:02
Screw binaries. Compile them by hand.
– Ярослав Рахматуллин
Commented Jun 21, 2011 at 15:06
My last experience of doing the same with httpd did not go down well unfortunately , but yes, it does seem like a time to take up arms :)
– Ricko M
Commented Jun 21, 2011 at 15:13

Add a comment |

dev4life · Accepted Answer · 2016-02-10 01:50:12Z

2

If curl_exec hangs, then it may be because of a DNS problem or a redirection loop. In other words, there may be nothing wrong with the function, but with the network route of your request. May be a deadlock with a localhost loop. Cheers!

answered Feb 10, 2016 at 1:50

dev4life

11.2k6 gold badges61 silver badges77 bronze badges

The php curl hangs forever, the sh curl works for the same url: http://localhost:4000/public/server.php. Server is the built-in php Server with php -S localhost:4000. curl php to https://reqbin.com/echo/get/json works, but not to the local address.
– Timo
Commented May 2, 2022 at 10:04

Add a comment |

user421944 · Accepted Answer · 2011-09-20 20:44:58Z

NSS is more strict than either OpenSSL or GnuTLS. Fedora/RHEL curl defaults to using NSS over OpenSSL, and can catch errors that don't arise using curl on OSX, Ubuntu, etc.

Here's a list of NSS error codes http://www.mozilla.org/projects/security/pki/nss/ref/ssl/sslerr.html

[root@mybox ~]# curl -k -v -E /etc/mycert.pem https://127.0.0.1/
* About to connect() to 127.0.0.1 port 443 (#0)
*   Trying 127.0.0.1... connected
* Connected to 127.0.0.1 (127.0.0.1) port 443 (#0)
* Initializing NSS with certpath: sql:/etc/pki/nssdb
* warning: ignoring value of ssl.verifyhost
* NSS error -8054
* Closing connection #0
* SSL connect error
curl: (35) SSL connect error

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