502 Bad Gateway

This definitely sounds like a configuration problem in either PHP or Apache.

Quote from stackoverflow:

A segementation fault is an internal error in php (or, less likely, apache). Oftentimes, the segmentation fault is caused by one of the newer and lesser-tested php modules such as imagemagick or subversion.

Try disabling all non-essential modules (in php.ini), and then re-enabling them one-by-one until the error occurs. You may also want to update php and apache.

Since this issue appears in different shops with the very same hosting provider, it is very likely that the issue is caused by the server setup. Are you able to configure any of this yourself with WPEngine?

I will try and check with WP Engine, since I can’t do anything about this myself.

However, I still find it hard to believe that the bug is at their end, since everything else on my site and all other plugins run fine. And that the old version of your plugin (2.1.5) also works fine.

But of course it’s also hard for you to check if you cannot reproduce the error.

Im positive that this is a combination of something in the plugin and something on the server causing the problem. If WPEngine is able to point out what might cause the problem, I can try modifying the plugin in a way that will work well with their setup as well.

So here’s the reply I got from WPEngine after they spent a lot of efforts on investigating it.

I hope I gives you some inout, so you can investigate further.

— Reply 1 —

Thanks for your patience with this.

I’ve generated a new staging area for testing, and I’m afraid I’m not making much progress. Even with all other plugins disabled and your theme reverted back to a standard theme, I’m still seeing that 502 error. It would appear the long query that was originally mentioned isn’t related. That query is related to tax tables in Woocommerce, and even with taxes disabled, I’m still seeing the error. So while we haven’t made much progress, we are (at least) ruling things out.

At this point, I’m pretty sure it’s plugin-related. Especially considering the older version of the plugin works fine.

Just to give it one more try, I’m going to get this sent up to our engineering team to have a look. Keep an eye on your email, and we’ll let you know as soon as we’ve heard back from them.

Thanks,

— Reply 2 —

Hi Peter,

I’ve spent quite a bit of time on this and unfortunately I haven’t had much luck. I was able to strace the process to see what was running before the seg fault and here’s what I got:

09:46:09.209430 rt_sigaction(SIGHUP, {0x7f2c07caf540, [], SA_RESTORER|SA_INTERRUPT, 0x7f2c0718dcb0}, {0x7f2c07caed10, [HUP USR1], SA_RESTORER, 0x7f2c0718dcb0}, 8) = 0
09:46:09.209632 rt_sigaction(SIGTERM, {0x7f2c07caf540, [], SA_RESTORER|SA_INTERRUPT, 0x7f2c0718dcb0}, {0x7f2c07caece0, [], SA_RESTORER, 0x7f2c0718dcb0}, 8) = 0
09:46:09.209805 rt_sigaction(SIGUSR1, {0x7f2c07caef20, [], SA_RESTORER|SA_INTERRUPT, 0x7f2c0718dcb0}, {0x7f2c07caed10, [HUP USR1], SA_RESTORER, 0x7f2c0718dcb0}, 8) = 0
09:46:09.210021 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2c060f3000
09:46:09.210200 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2c060f1000
09:46:09.210327 geteuid()               = 0
09:46:09.210430 setgid(33)              = 0
09:46:09.210546 open("/proc/sys/kernel/ngroups_max", O_RDONLY) = 48
09:46:09.210719 read(48, "65536\n", 31) = 6
09:46:09.210845 close(48)               = 0
09:46:09.211369 open("/etc/group", O_RDONLY|O_CLOEXEC) = 48
09:46:09.211584 lseek(48, 0, SEEK_CUR)  = 0
09:46:09.211750 fstat(48, {st_mode=S_IFREG|0644, st_size=3127, ...}) = 0
09:46:09.211903 mmap(NULL, 3127, PROT_READ, MAP_SHARED, 48, 0) = 0x7f2c060f0000
09:46:09.212013 lseek(48, 3127, SEEK_SET) = 3127
09:46:09.212160 lseek(48, 252, SEEK_SET) = 252
09:46:09.212275 fstat(48, {st_mode=S_IFREG|0644, st_size=3127, ...}) = 0
09:46:09.212434 lseek(48, 3127, SEEK_SET) = 3127
09:46:09.212538 lseek(48, 252, SEEK_SET) = 252
09:46:09.212642 fstat(48, {st_mode=S_IFREG|0644, st_size=3127, ...}) = 0
09:46:09.212785 lseek(48, 3127, SEEK_SET) = 3127
09:46:09.212898 fstat(48, {st_mode=S_IFREG|0644, st_size=3127, ...}) = 0
09:46:09.213041 munmap(0x7f2c060f0000, 3127) = 0
09:46:09.213148 close(48)               = 0
09:46:09.213252 setgroups(1, [33])      = 0
09:46:09.213353 geteuid()               = 0
09:46:09.213443 setuid(33)              = 0
09:46:09.213623 gettid()                = 2971
09:46:09.213737 open("/proc/2971/attr/current", O_WRONLY) = 48
/Seg
09:46:26.178179 close(52)               = 0
09:46:26.178287 fcntl(51, F_GETFL)      = 0x8000 (flags O_RDONLY|O_LARGEFILE)
09:46:26.178390 fstat(51, {st_mode=S_IFREG|0664, st_size=7093, ...}) = 0
09:46:26.178526 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2c0195c000
09:46:26.178616 lseek(51, 0, SEEK_CUR)  = 0
09:46:26.178701 lseek(51, 0, SEEK_SET)  = 0
09:46:26.178789 read(51, "<?php\n/**\n * Checkout Shortcode\n"..., 4096) = 4096
09:46:26.178909 lseek(51, 4096, SEEK_SET) = 4096
09:46:26.178989 stat("/nas/wp/www/cluster-10624/jsontesting/wp-content/plugins/woocommerce/includes/shortcodes/class-wc-shortcode-checkout.php", {st_mode=S_IFREG|0664, st_size=7093, ...}) = 0
09:46:26.179238 munmap(0x7f2c0195d000, 7093) = 0
09:46:26.179357 lseek(51, -4096, SEEK_CUR) = 0
09:46:26.179440 close(51)               = 0
09:46:26.179520 munmap(0x7f2c0195c000, 4096) = 0
09:46:26.182305 --- SIGSEGV (Segmentation fault) @ 0 (0) ---

This just tells us that during the checkout process it encounters a segmentation fault. There really isn’t much more we can do to troubleshoot at this point.

I’d pass this to the developer to see if helps! If he has any questions for us, please let us know!

WP Engine

Hi

Just wanted to let you know that I have the exact same problem. My webshop is hosted at WPengine.com and when I move forward from checkout page to quickpay payment gateway, I get a 502 Bad gateway error… ??

Sure hope someone can figure this out… ??

/David

Hello,

I also get the 502 problem when i use the newest version of the plugin. And when i download the old 2.1.5 then it works again.

The problems with 502 Bad Gateway on checkout, mainly on wpengine hosted websites, has been solved in the newly released 3.0.5.

I have just updated the plugin and tested everything. It works as a charm – even on WP Engine.

Thank you so much for pursuing this and fixing it.