PayPal iPN intermittant failure HTTP error 500

We recently moved to a new ISP. Almost all transactions
are being processed to completion, but a few (less than
5%) are receiving IPN error 500, an HTTP error of a general
nature with no further information available.

I've requested our ISP to look at the Apache logs for those
dates and times to see if there is any information in the
logs that might help, but haven't heard back yet.

Searching for threads on the issue turn up 1.3.8-era problems
from 2008 and 2009, so they're not current.

Is there anything I can be doing to track down this anomaly?

Thanks.

Dr Doug

d0ugparker:

We recently moved to a new ISP. Almost all transactions
are being processed to completion, but a few (less than
5%) are receiving IPN error 500, an HTTP error of a general
nature with no further information available.

I've requested our ISP to look at the Apache logs for those
dates and times to see if there is any information in the
logs that might help, but haven't heard back yet.

Searching for threads on the issue turn up 1.3.8-era problems
from 2008 and 2009, so they're not current.

Is there anything I can be doing to track down this anomaly?

Thanks.

Dr Doug

Is there a reason the less problematic paypal express isn't used, or is this occurring with it?

I don't understand the interplay between ZC and
PP, its communications protocol, or its required
settings. I don't even know if IPN is something
that I need to have enabled or not for our site
to work properly. I really don't know how best
to go forward on this.

If PayPal's Instant Payment Notification (IPN)
isn't needed for generic ZC / PP processing, then
I can easily shut it off and be done with it, but
I'm afraid of shutting down the IPN feature and
having the site dead in the water.

I'm lost.

I just found this link, and I'm reviewing it:

Why am I getting 500 INTERNAL SERVER ERROR messages?

It's on ZenCart support. I know we're using IIS, so that's
already a not so good indicator. :(

Regarding paypal and paypal's ipn, take a look at the following as well:

About setting up a portion of the IPN information:
http://www.zen-cart.com/content.php?116-how-do-i-set-up-paypal-ipn-to-return-to-my-store-automatically

Which leads to the below link if selected at the top.

For paypal setup instructions:
Documents in the installation package and,
http://www.zen-cart.com/wiki/index.php/PayPal
As well as the instructions provided in the admin panel when modules, payments, and the applicable/desired payPal option is selected.

For a generic, vanilla ZenCart installation, with
no special, customized features programmed in
on our ZenCart side (just the ordinary, out-of-
the-box install that's done from the start),

1. do I even need to have IPNs activated, or
2. are the IPNs the method by which basic
   purchase confirmations are communicated back
   and forth between ZenCart and PayPal?

PayPal allows a setting to disable IPNs if I don't
want them. Again, I'm not clear on the purpose
of the IPNs. Were I to disable IPNs, would I
effectively shut down our online shopping
service? :-\

sigh

d0ugparker:

For a generic, vanilla ZenCart installation, with
no special, customized features programmed in
on our ZenCart side (just the ordinary, out-of-
the-box install that's done from the start),

1. do I even need to have IPNs activated, or
2. are the IPNs the method by which basic
   purchase confirmations are communicated back
   and forth between ZenCart and PayPal?

PayPal allows a setting to disable IPNs if I don't
want them. Again, I'm not clear on the purpose
of the IPNs. Were I to disable IPNs, would I
effectively shut down our online shopping
service? :-\

sigh

What paypal method is being used?

Keep saying generic paypal and the like, but there is more than one paypal method available. Paypal standard works solely via IPN and disabling it from the paypal side would disable that method of payment. Paypal express (which is also avail with a basic install of ZC does have some uses for it, but I forget the impact.

After some in depth myPHPAdmin sleuthing, PayPal
IPN error log reviews, and individual ZenCart invoice
lookups, the commonality I've found among all
of the orders with failed IPN notifications was that
for that brief period of time, all the error messages
were being generated with a payment method of

paypalwpp

All paypalwpp orders failed during that window of
time. All other orders went through, some with
paypaldp, some with moneyorder payment method.

Not all paypalwpp-related payments are failing –
there have been no IPN failures reported for the
last week on our installation. I really don't have
enough knowledge to know what a paypalwpp
failure means, nor where to turn next for my next
step in the process I'm in the middle of.

I don't mean to skirt around answering the
question of payments and methods, but ZenCart
has its own name for the communications it does
with payment gateways (i.e., PayPal, and I'm not
sure I'm even using the word 'gateway' in the
correct context), PayPal has its own naming of
the services it offers to different online shopping
carts, and PayPal's multiple services each provide
different features. I could understand it if it were
laid out in front of me, but I've never seen anything
that describes its construction well enough to know
what it is that's being laid down in front of me. I'm
a fairly bright guy, but right now, I'm confused. I'm
lost.

This is all starting to clear up to what seems to indicate
there being some sort of IIS server issue, that it's not
ZenCart, and not PayPal. IIS is, after all, not the 100%
reliable installation platform, and I found that out after
moving our cart over and researching the server
platform we were on.

I wish I were in a better space understanding it all
so I could definitively say what it was that I needed,
but seriously, I'm building this boat as I row it. :-j

d0ugparker:

After some in depth myPHPAdmin sleuthing, PayPal
IPN error log reviews, and individual ZenCart invoice
lookups, the commonality I've found among all
of the orders with failed IPN notifications was that
for that brief period of time, all the error messages
were being generated with a payment method of

paypalwpp

All paypalwpp orders failed during that window of
time. All other orders went through, some with
paypaldp, some with moneyorder payment method.

Not all paypalwpp-related payments are failing –
there have been no IPN failures reported for the
last week on our installation. I really don't have
enough knowledge to know what a paypalwpp
failure means, nor where to turn next for my next
step in the process I'm in the middle of.

I don't mean to skirt around answering the
question of payments and methods, but ZenCart
has its own name for the communications it does
with payment gateways (i.e., PayPal, and I'm not
sure I'm even using the word 'gateway' in the
correct context), PayPal has its own naming of
the services it offers to different online shopping
carts, and PayPal's multiple services each provide
different features. I could understand it if it were
laid out in front of me, but I've never seen anything
that describes its construction well enough to know
what it is that's being laid down in front of me. I'm
a fairly bright guy, but right now, I'm confused. I'm
lost.

This is all starting to clear up to what seems to indicate
there being some sort of IIS server issue, that it's not
ZenCart, and not PayPal. IIS is, after all, not the 100%
reliable installation platform, and I found that out after
moving our cart over and researching the server
platform we were on.

I wish I were in a better space understanding it all
so I could definitively say what it was that I needed,
but seriously, I'm building this boat as I row it. :-j

Yes there are "flavors" of paypal implementation, but we are here talking about zencart, and questions are being asked about the settings in zen cart. When looking in the admin panel under modules->payments, what paypal lines have a green dot to the right of the name?

***Check/Money Order
PayPal PaymentsPro
PayPal Express Checkout

are the modules installed.

I noticed that PayPal PaymentsPro requires CURL
and must be able to use SSL. Indicators are that
my admin is not set up for SSL – surprise, I'd thought
that had been configured in the config.php, but
apparently not.

Am I correct in thinking that the config.php needs
to be changed to have my admin running SSL, and
that this could be the cause of the non-communication
between PayPal and my ZenCart installation?

d0ugparker:

***Check/Money Order
PayPal PaymentsPro
PayPal Express Checkout

---

are the modules installed.

I noticed that PayPal PaymentsPro requires CURL
and must be able to use SSL. Indicators are that
my admin is not set up for SSL – surprise, I'd thought
that had been configured in the config.php, but
apparently not.

Am I correct in thinking that the config.php needs
to be changed to have my admin running SSL, and
that this could be the cause of the non-communication
between PayPal and my ZenCart installation?

If paypalwpp is the issue, from a quick net search that is indication that there is/was a problem with paypal express. Paypal express uses curl and should also be able to communicate (telnet on port 443) securely to the paypal system. That said, the settings should also be verified correct to be sure.

Check out this thread about getting started with paypal although it has already "begun" :)
http://www.zen-cart.com/content.php?20-PayPal
I did find a thread indicating that there is/was a test performed when using paypal paymentspro to verify that the admin was ssl, but dr. Byte provided a correction to lat9 on the issue and this has been incorporated into 1.5.2+ if it is/was a problem you more than likely also received an email related to that aspect when the sale was trying to be processed indicating something to the effect that the site was not secure or something... That "message" hasn't been reported here, so I'm not so sure it is the issue, but wouldn't be the first (nor last) time I was wrong about something.

mc12345678:

If paypalwpp is the issue, from a quick net search that is indication that there is/was a problem with paypal express. Paypal express uses curl and should also be able to communicate (telnet on port 443) securely to the paypal system. That said, the settings should also be verified correct to be sure.

Check out this thread about getting started with paypal although it has already "begun" :)
http://www.zen-cart.com/content.php?20-PayPal

Yup, all that's been done, and unfortunately
doesn't help me further my understanding of
the structure of the model in use.

mc12345678:

I did find a thread indicating that there is/was a test performed when using paypal paymentspro to verify that the admin was ssl, but dr. Byte provided a correction to lat9 on the issue and this has been incorporated into 1.5.2+ if it is/was a problem you more than likely also received an email related to that aspect when the sale was trying to be processed indicating something to the effect that the site was not secure or something... That "message" hasn't been reported here, so I'm not so sure it is the issue, but wouldn't be the first (nor last) time I was wrong about something.

The 500 error I'm receiving is a generic error
without further explanation. The following XML
code was what I received from my ISP that I
can reportedly add to my web.config file to get
more detailed failure messages reported in my
error logs:

**```
<configuration>
<system.webServer>
<httpErrors errorMode="Detailed"/>
</system.webServer>
</configuration>

I haven't added it yet. I'm currently waiting for 
their tech support to confirm the SSL on 80 and 
443. Then I need to go looking for my config.php 
and check my SSL status there. 

When I add the XML, the error may raise its head 
again, in which case I'll hopefully have a better 
snapshot taken of its failure mode. 

Then? I dunno. :-j

d0ugparker:

Yup, all that's been done, and unfortunately
doesn't help me further my understanding of
the structure of the model in use.

The 500 error I'm receiving is a generic error
without further explanation. The following XML
code was what I received from my ISP that I
can reportedly add to my web.config file to get
more detailed failure messages reported in my
error logs:

**```
<configuration>
<system.webServer>
<httpErrors errorMode="Detailed"/>
</system.webServer>
</configuration>

> I haven't added it yet. I'm currently waiting for 
> their tech support to confirm the SSL on 80 and 
> 443. Then I need to go looking for my config.php 
> and check my SSL status there. 
> 
> When I add the XML, the error may raise its head 
> again, in which case I'll hopefully have a better 
> snapshot taken of its failure mode. 
> 
> Then? I dunno. :-j

Sounds like a plan, though I wouldn't wait for the tech response in order to implement the tracking code. Personal choice, but might as well try to gather other information especially if the effect were to log something that might help the tech(s).

After a week of no IPN retries or failures, I've
received 13 today. I'll be checking phpMyAdmin,
PayPal, and ZenCart to see if the same pattern
holds.

I implemented the addition web.server code,
but not in time to generate any additional,
verbose error messages with the 13 new retries
PayPal effected today.

Update: All IPN retries on 9/17, today, that PayPal
is needing to resend are being caused by paypalwpp
payment transactions. This is the same condition I
uncovered earlier.

Our ZenCart installation was copied to a subdomain

ourstore.ourdomain.org

and the SSL certificate is listed as covering that
subdomain

ourstore.ourdomain.org

yet if I log in to the admin side, I'm not getting
an HTTPS indicated in the address bar, only HTTP.
ZenCart is said to be smart enough to know when
to enable HTTPS, but have I set all the proper
switches to tell ZenCart to do so? In the old version
of ZenCart, there used to be a separate setting
for ADMIN and for CATALOG SSLs. I wonder if
that's been wrapped up into the few lines below.

I've checked my includes/configure.php file, and
I have these settings

  define('HTTP_SERVER', 'http://ourstore.ourdomain.org');
  define('HTTPS_SERVER', 'https://ourstore.ourdomain.org');

  define('ENABLE_SSL', 'true');

  define('DIR_WS_CATALOG', '/');
  define('DIR_WS_HTTPS_CATALOG', '/');

I'll know more as I get more detailed HTTP error
reporting in my log file.

The https for the YourAdmin is NOT covered by the includes/configure.php but by the YourAdmin/includes/configure.php. You will need to set both the http_server and https_server to https://.....

It is NOT recommended to do this in the includes/configure.php as you only need the cart to be in secure mode when logging in or checking out.