Within httpd.conf or vhosts file it’s possible to:
log all errors to a log file using http://httpd.apache.org/docs/1.3/mod/core.html#errorlog
forward a user on to a custom error page depending on what the error code is http://httpd.apache.org/docs/2.0/mod/core.html#errordocument
Are there any other alternatives to dealing with apache error? What i'd really like to do is somehow get hold of an apache error when it occurs in php.
(We're looking to build a tool which monitors errors that occur globally on our servers in a web based interface (using php). Currently I'm thinking of logging errors to a log file and then use php to monitor this file for changes and parse it in to something usable with PHP.)
You can use the ErrorDocument directive to redirect errors to your own PHP application that:
Displays an error message to the user, and
Performs any other work necessary to handle the error.
That is, the target of your ErrorDocument does not need to be simply a static error page; it can be any URL you want and you can take whatever action you would like in response to the request.
This will probably be more effective than scraping the log.
Related
I have two servers. They are both running the same code and are connected to the same database. But when I make a certain ajax call, one server works fine, and the other throws an Internal Server Error. Inside the Apache log of the internal service error server, it says 'Premature end of script headers'. This makes me think that there is some Apache error on one machine, but the Apache folder looks identical on both machines.
What sort of differences between servers would cause one to throw this error?
The error tells that you that no headers were output where they should be output. Typically it happens with a cgi script that fails for some reason and hence does not output anything, or outputs stuff before outputting the headers.
To debug it: Look in the apache error log. It will most likely tell you what went wrong.
To find the error_log: Look for the ErrorLog directive in the apache configuration file.
Swa66 etc have provided good answers but I thought that I would add a few more things to look into after you you reviewed the apache error logs which should give you the text that was returned where Apache was expecting a valid http header.
You mentioned that the servers are responding to Ajax queries and so it is possible that you are having some kind of CORS issues or issues relating to how Apache is configured to allow HTTP headers to be passed through to the CGI process.
It is not uncommon to include JWT or other auth headers as part of an ajax service and you may find that you need to add either a .htaccess file permitting these to flow through
Check your working server to see if the headers module is enabled ( - something like this in you httpd.conf - LoadModule headers_module libexec/apache2/mod_headers.so )
Also look for the .htaccess or domain specific configuration of the header related options. If need be, have a dig around relating to Apache CORS configuration and header related issues.
You may need some kinds of configuration similar to the following.
.htaccess
SetEnvIf Authorization .+ HTTP_AUTHORIZATION=$0
Header set Access-Control-Allow-Origin "*"
It is a little difficult to be certain of your issue without more specific diagnostics. Perhaps you could provide debugger details from your browser describing the Ajax/XHR requests including the headers etc and the relevant error log entries from apache. Assuming that you are using Perl/CGI perhaps snippets describing the CGI configuration from the config and any .htaccess files on the working and errant server.
You may also want to do a quick check of the permissions of the executables and try to run them from the command line.
It could be a very basic configuration option such as described at apache centos fails to serve images - premature end of script headers .. we really need a little more diagnostic detail to focus on possible causes.
I want to you Apache 2.2 httpd to SSI include URLs using
<!--#include virtual="/content/foo.html" -->
My problem is if, the SSI included page doesnt exist on my App server, it responds with a 404 response and a default error page HTML, which is then stitched into my page via the include.
For failing (4xx,5xx) SSI includes I simply want the SSI include to add the empty string to my page.
It doesn't appear Apache 2.2. supports the 'onerror' directive (which I think would solve this) - and i dont see any other options.
http://httpd.apache.org/docs/2.2/mod/mod_include.html
You could potentially add a rewrite to handle those portions of your application's URI space, but I'd advise against it. The approach being investigated seems to not fix the main problem: the concept of SSIs hinges on the files being included should be consistently available. If the included files are returning 4xx or 5xx class errors, the onus is on you to fix these errors.
I've discovered from Google Webmaster Tools that Google has found a bad link somewhere that is throwing a 403 error on my server.
The url is like this:
http://www.example.com/directory/.php
I don't know how that url has come about and the site is too complicated for me to find out, but I'd like to simply place a 301 redirect to:
http://www.example.com/directory/
I've put the correct rule in .htaccess for the redirect, but it doesn't appear to be triggered. It's almost as if the 403 is being generated before .htaccess is processed. Does anyone know why this might be and how I can successfully get the user redirected to the new page?
Except for the fact that the rule may be indeed incorrect, this could also be because this involves looking for a file with a filename starting with a ..
These files are usually "hidden" from the outside world, so it might be that either your Apache (configuration) or your OS does not allow serving this file.
Without knowing more about the configuration, this cannot be analyzed though. You could test it by creating a file called ".test" and see if that's reachable.
I had a hard time deciding how I should manage these errors (404, 500, ...) and when I finally decided, I am encountering problems. This is a reeeeeally long question, I appreciate anyone's attempt to help!
Let me first describe how I decided to set it up. I have several sites hosted on a shared Dreamhost account. In the folder structure that I see, everything of mine on the server is under /home/username, and for example, site1.com's web root is at /home/username/site1.com
I am creating a generic error handler (php script) for errors like 404 not found, 500, etc. that I want to store above the web roots of my sites at /home/username/error_handler/index.php so that I can use an .htaccess file at /home/username/.htaccess which includes something like the following:
ErrorDocument 404 /error_handler/index.php
ErrorDocument 500 /error_handler/index.php
...and many more
When these errors occur on any of my sites, I want it to be directed to /home/username/error_handler/index.phpThis is the problem I'm having a hard time figuring out. The ErrorDocument directives above will actually cause Apache to look for /home/username/site1.com/error_handler/index.php
Anyway, the errors should be redirected to my error handling php script. The script will use $_SERVER['REDIRECT_STATUS'] to get the error code, then use $_SERVER['REDIRECT_URL'] and $_SERVER['HTTP_HOST'] to decide what to do. It will check if an error handler specific to that site exists (for example: site1.com/errors/404.php). If this custom page doesn't exist, it will output a generic message that is slightly more user-friendly and styled, and perhaps will include some contact info for me depending on the error.
Doing it this way lets me funnel all these errors through this 1 php script. I can log the errors however I like or send email notifications if I want. It also lets me set up the ErrorDocument Apache directives once for all my sites instead of having to do it for every site. It will also continue to work without modification when I move the site around, since I already have a system that scans the folder structure to figure out where my site roots are when they really aren't at the web root technically speaking. This may not be possible with other solutions like using mod_rewrite for all 404 problems, which I know is common. Or if it is possible, it may be very difficult to do. Plus, I have already done that work, so it will be easy for me to adapt.
When I am working on sites for which I don't have a domain name yet (or sites where the domain name is already in use at the moment), I store them temporarily in site1.com/dev/site3.com for example. Moving the site to site3.com eventually would cause me to have to update the htaccess files if I had one for each site. Changing the domain name would do the same.
Ex: a site stored at site1.com/dev/site3.com would have this in its htaccess file:
ErrorDocument 404 /site1.com/dev/site3.com/error/404.php
And it would have to be changed to this:
ErrorDocument 404 /site3.com/error/404.php
Obviously, this isn't a huge amount of work, but I already manage a lot of sites and I will probably be making more every year, 95% of which will be hosted on my shared DreamHost account. And most of them get moved at least once. So setting up something automatic will save me a some effort in the long run.
I already have a system set up for managing site-relative links on all my sites. These links will work whether the site exists in a subdirectory of an existing site, or in their own domain. They also work without change in a local development server despite a difference in the web root location. For example, on the live server, the site-relative http link /img/1.jpg would resolve to the file /home/username/site1.com/img/1.jpg while on my local development server it would resolve to C:\xampp\htdocs\img\1.jpg, despite what I consider the logical site root being at C:\xampp\htdocs\site1.com. I love this system, and it is what gave me the idea to set up something that would work automatically like I expected it to, based on the file structure I used.
So, if I could get it to work, I think this seems like a pretty good system. But I am still very new to apache configuration, mod_rewrite, etc. It's possible there is a much easier and better way to do this. If you know of one, please let me know.
Anyway, all that aside, I can't get it working. The easiest thing would be if I could have the ErrorDocument directive send the requests to folders above the web root. But the path is a URL path relative to the document root. Using the following in /home/username/.htaccess,
ErrorDocument 404 /error_handler/index.php
a request for a non-existent resource causes Apache to look for the file at
site1.com/error_handler/index.php
So I thought I should set up a redirection (on all my sites) that would redirect those URLS to /home/username/error_handler. I tried a few things and couldn't get any of them to work.
Alias seemed like the simplest solution, but it is something that has to be set at server runtime (not sure if that is the right terminology - when the server is started). On my local server, it worked fine using:
Alias /error_handler C:\xampp\htdocs\error_handler2
I changed the local folder to test that the Alias was functioning properly. (On the local server, the URL path specified by the ErrorDocument directive is actually pointing to the right folder, since in my local server the web root is technically C:\xampp\htdocs and I store the error handler I want to use is stored locally at C:\xampp\htdocs\error_handler\index.php)
Dreamhost has a web client that can create what I am guessing is an Alias. When I tried to redirect the folder error_handler on site1.com to /home/username/error_handler, it would seem to work right if I typed site1.com/error_handler in the browser. But if I typed site1.com/test1234 (non-existant), it would say there was a 404 error trying to use the error handler. Also, I would have to login through the web client and point and click (and wait several minutes for the server to restart) every time I wanted to set this up for a new site, even if I could get it to work.
So I tried getting it to work with mod_rewrite, which seems like the most flexible solution. My first attempt looked something like this (stored in /home/username/site1.com/.htaccess for now, though it would eventually be at /home/username/.htaccess:
RewriteEngine On
RewriteRule ^error_handler/index.php$ /home/username/error_handler/index.php
The plain english version of what I was trying to do above is to send requests on any of my sites for error_handler/index.php to /home/username/error_handler/index.php. The mis-understanding I had is that the subsitution will be treated as a file path if it exists. But I missed that the documentation says "(or, in the case of using rewrites in a .htaccess file, relative to your document root)". So instead of rewriting to /home/username/error_handler/index.php, it's actually trying to rewrite to /home/username/site1.com/home/username/error_handler/index.php.
I tried including Options +FollowSymLinks because in the Apache documentation it says this:
To enable the rewrite engine in this context [per-directory re-writes in htaccess], you need to set "RewriteEngine On" and "Options FollowSymLinks" must be enabled. If your administrator has disabled override of FollowSymLinks for a user's directory, then you cannot use the rewrite engine. This restriction is required for security reasons.
I searched around for a while and I couldn't find anything about how Dreamhost handles this (probably because I don't know where to look).
I experimented with RewriteBase because in the Apache documentation it says this:
"This directive is required when you use a relative path in a substitution in per-directory (htaccess) context unless either of the following conditions are true:
The original request, and the substitution, are underneath the DocumentRoot (as opposed to reachable by other means, such as Alias)."
Since this is supposed to be a URL path, in my case it should be RewriteBase /, since all my redirects will be from site1.com/error_handler. I also tried Rewrite Base /home/username and RewriteRule ^error_handler/index.php$ error_handler/index.php. However, the Rewrite Base is a URL path relative to the document root. So I need to use something like an alias still. The implication in the quote from the documentation above is that it is possible to use mod_rewrite to send content above the web root. One of the many things I don't know is what the 'other means' besides Alias might be. I believe Alias might not be an option on Dreamhost. At least I couldn't make sense of it.
Why not use error pages in the site root, then include the actual file from the shared section?
I'm building a web tool which allows users to upload PDFs to a server using their web browsers. The server is based on Python (Paste + Pyramid).
The problem I have right now is the following: If a user uploads a rather large file (let's say 100 MB) and they cancel the upload before it is completed, my handler code on the server is still called (instead of the request being aborted).
The problem is that the request.POST['myfile'].file is incomplete when that happens. This effectively means that the PDF file is corrupted if I simply write it to some place on the server.
When I watch the server's log, it shows a "broken pipe" exception within the Paste server; however I have no idea how to catch that exception and have it prevent my view/handler code from executing and storing the incomplete file.
Seems like the paster HTTP server does not correctly validate the uploaded form data and simply passes the request down the WSGI pipeline even if the connection (HTTP POST) was closed by the user.
I worked around this issue by simply setting up NGINX to act as a reverse proxy. This also adds some security benefits as it might be better tested than paster.
Update:
My main problem was that I was using runserver (the built in web server of manage.py). After some trial and error we ended up using WSGI.
More specifically, uWSGI and Nginx as web server. Static content is served directly by Nginx while dynamic pages are piped through uWSGI and are handled by the Python web app.
Unless you are doing something fancy (like tracking the upload progress, etc), your pylons controller should not be invoked until the entire file has been uploaded.