Reading Time: 4minutes
I've recenty tried Update my WordPress blog sites and being unattentive I've selected all the plugins possitble for Upgrade by checking the "Select All" check box on the Update dialogs and almost automatically int he hurry pressing Update button however out of a sudden I've realized I could screw up my websites brutally as some of the plugins to upgraded might be lacking 100% compitability with their prior versions.
I've made a messes out of my blog many times during upgrades because of choosing to upgrade the wrong not 100% compatible plugins and I know well how painful and hard to track it could be a misbehaving incompatible plugin or how ot could cause a severe sluggishness to blog which automatically reflects on how well the website search engine ranked in Google / Yahoo / Bing indexed etc.
Thus as an almost unconcsious reaction to prevent myself the future troubles I've tried to cancel the update request in Firefox browser and trying to reload the Update page with a hope that I might be quick enough for the Apache / WP / MySQLbackend Update Update queries request to be delaying for processing but I was too slow and bang! I ended up with the following unpleasent message in my browser:
Briefly unavailable for scheduled maintenance.
As you could guess that message caused me quite a lot of worries at hand especially since I've already break up my sites many times by doing quick unmindful reactions and the fact that there is Google Adsense ads appearing which does give me some Return on Investment cents every now and then …
It took me few minutes of research online to find what really happened and how to fix / resolve the WebSites normal operations.
So what causes the Briefly unavailable for scheduled maintenance. appears ?
When WordPress does some of its integrated maintenance jobs a plugin enable / disable or any task that has to modify crucial configurations inside the database WordPress does disable access to all end clients to itself in order to protect its sensitive data to appear to browser requestors as showing some unexpected information to end client browser could be later used by crackers / hackers or a possibly open a security hole for an attacker.
The message is wordpress generated notice and it is pretty normal for the end user to see it during the WP site installation update depending on how many plugins are installed and loaded to the site and how long it will take for the backend Linux / Windows server to fetch the archived .zips of plugins and substitute with the new ones and update the files extracting them to wp-content/plugins and updating the respective required SQL database / tables it could be showing for end users from few secs to few minutes.
However under some circumstances on Browser request timeout to remote wordpress site due to a network connectivity issue or just a bad configuration of Apache for requests timeout (or a slow remote server Apache responce time due to server Hardware / Mem overload) or a stupid browser "Stop" / cancel request like in my case you end up with the Briefly unavailable for scheduled maintenance and you can can longer access the your https://siteurl.com/wp-admin Admin Panel.
The message is triggered by a WP craeted file .maintenance inside /var/www/blog-site/ e.g. WordPress PHP scripts does check for/var/www/blog-site/.maintenance
existence and if it is matched the WP scripts does generate the Briefly unavailble … message.
How to resolve the "Briefly unavailable for scheduled maintenance. Check back in a minute" WordPress error ?
As you might guess removing the maintenance "coming soon" like message in most of the cases comes to just deleting the .maintenance file, to do so:
1. Login to remote server via FTP or SFTP
2. Locate your WP website root folder that should be something like /var/www/blog-site/.maintenance and issue:
issue something like:
$ rm -rf /var/www/bog-site/.maintenance
Assuming that some plugin Update .zip extraction or SQL update query did not ended being half installed/ executedthat should solve the error.
To check whether all is back to normal just refresh your browser pointing to the "broken" site. If it appears well you can thank God for that 🙂
If not check the apache error logs and php error logs and see which of the php scripts is failing and then try to manually fetch and unzip the WP .zip package to wp-content/plugins folder and give it another try and if God bless so it will work as before 🙂
How to prevent your WP based business in future from such nasty errors using A Staging site (test) version of your blog ?
Just run a duplicate of your website under a separate folder on your hosting and do enable the same plugins as on the primary website and copy over the MySQL / PostgreSQL Database from your Live site to the Staging, then once it is enabled before doing any crucial WordPress version updates or Plugins Update always do try the Upgrade first on your Test Staging site. If it does execute fine there in most of the cases the result should be the same on the Production host and that could solve you effors and nerves of debugging a hard to get failure errors or faulty plugins without affecting what your End users see.
If you're not hosting the WordPress install under your own hosting like me you can always use some of the public available hostings like BlueHost or WPEngine
How to resolve (fix) WordPress wp-cron.php errors like “POST /wp-cron.php?doing_wp_cron HTTP/1.0″ 404” / What is wp-cron.php and what it does
Monday, March 12th, 2012Reading Time: 5minutes
One of the WordPress websites hosted on our dedicated server produces all the time a wp-cron.php 404 error messages like:
xxx.xxx.xxx.xxx - - [15/Apr/2010:06:32:12 -0600] "POST /wp-cron.php?doing_wp_cron HTTP/1.0
I did not know until recently, whatwp-cron.php does, so I checked in google and red a bit. Many of the places, I've red are aa bit unclear and doesn't give good exlanation on what exactly wp-cron.php does. I wrote this post in hope it will shed some more light on wp-config.php and how this major 404 issue is solved..
So
what is wp-cron.php doing?
Suppose you're writting a new post and you want to take advantage of WordPress functionality to schedule a post to appear Online at specific time:
The Publish Immediately, field execution is being issued on the scheduled time thanks to the wp-cron.php periodic invocation.
Another example for wp-cron.php operation is in handling flushing of WP old HTML Caches generated by some wordpress caching plugin like W3 Total Cache
wp-cron.php takes care for dozens of other stuff silently in the background. That's why many wordpress plugins are depending heavily on wp-cron.php proper periodic execution. Therefore if something is wrong with wp-config.php, this makes wordpress based blog or website partially working or not working at all.
Our company wp-cron.php errors case
In our case the:
212.235.185.131 – – [15/Apr/2010:06:32:12 -0600] "POST /wp-cron.php?doing_wp_cron HTTP/1.0" 404
is occuring in Apache access.log (after each unique vistor request to wordpress!.), this is cause wp-cron.php is invoked on each new site visitor site request.
This puts a "vain load" on the Apache Server, attempting constatly to invoke the script … always returning not found 404 err.
As a consequence, the WP website experiences "weird" problems all the time. An illustration of a problem caused by the impoper wp-cron.php execution is when we are adding new plugins to WP.
Lets say a new wordpress extension is download, installed and enabled in order to add new useful functioanlity to the site.
Most of the time this new plugin would be malfunctioning if for example it is prepared to add some kind of new html form or change something on some or all the wordpress HTML generated pages.WP cache directory is manually deleted with rm -rf /var/www/blog/wp-content/cache/…
This troubles are result of wp-config.php's inability to update settings in wp SQL database, after each new user request to our site.
So the newly added plugin website functionality is not showing up at all, until
I don't know how thi whole wp-config.php mess occured, however my guess is whoever installed this wordpress has messed something in the install procedure.
Anyways, as I researched thoroughfully, I red many people complaining of having experienced same wp-config.php 404 errs. As I red, most of the people troubles were caused by their shared hosting prohibiting the wp-cron.php execution.
It appears many shared hostings providers choose, to disable the wordpress default wp-cron.php execution. The reason is probably the script puts heavy load on shared hosting servers and makes troubles with server overloads.
Anyhow, since our company server is adedicated server I can tell for sure in our case wordpress had no restrictions for how and when wp-cron.php is invoked.
I've seen also some posts online claiming, the wp-cron.php issues are caused of improper localhost records in /etc/hosts, after a thorough examination I did not found any hosts problems:
hipo@debian:~$ grep -i 127.0.0.1 /etc/hosts
127.0.0.1 localhost.localdomain localhost
You see from below paste, our server, /etc/hosts has perfectly correct 127.0.0.1 records.
Changing default way wp-cron.php is executed
As I've learned it is generally a good idea for WordPress based websites which contain tens of thousands of visitors, to alter the default way wp-cron.php is handled. Doing so will achieve some efficiency and improve server hardware utilization.
Invoking the script, after each visitor request can put a heavy "useless" burden on the server CPU. In most wordpress based websites, the script did not need to make frequent changes in the DB, as new comments in posts did not happen often. In most wordpress installs out there, big changes in the wordpress are not common.
Therefore, a good frequency to exec wp-cron.php, for wordpress blogs getting only a couple of user comments per hour is, half an hour cron routine.
To disable automatic invocation of wp-cron.php, after each visitor request open /var/www/blog/wp-config.php and nearby the line 30 or 40, put:
define('DISABLE_WP_CRON', true);
An important note to make here is that it makes sense the position in wp-config.php, where define('DISABLE_WP_CRON', true); is placed. If for instance you put it at the end of file or near the end of the file, this setting will not take affect.
With that said be sure to put the variable define, somewhere along the file initial defines or it will not work.
Next, with Apache non-root privileged user lets say www-data, httpd, www depending on the Linux distribution or BSD Unix type add a php CLI line to invoke wp-cron.php every half an hour:
linux:~# crontab -u www-data -e
0,30 * * * * cd /var/www/blog; /usr/bin/php /var/www/blog/wp-cron.php 2>&1 >/dev/null
To assure, the php CLI (Command Language Interface) interpreter is capable of properly interpreting the wp-cron.php, check wp-cron.php for syntax errors with cmd:
linux:~# php -l /var/www/blog/wp-cron.php
No syntax errors detected in /var/www/blog/wp-cron.php
That's all, 404 wp-cron.php error messages will not appear anymore in access.log! 🙂
Just for those who can find the root of the /wp-cron.php?doing_wp_cron HTTP/1.0" 404 and fix the issue in some other way (I'll be glad to know how?), there is also another external way to invoke wp-cron.php with a request directly to the webserver with short cron invocation via wget or lynx text browser.
– Here is how to call wp-cron.php every half an hour with lynxPut inside any non-privileged user, something like:
01,30 * * * * /usr/bin/lynx -dump "http://www.your-domain-url.com/wp-cron.php?doing_wp_cron" 2>&1 >/dev/null
– Call wp-cron.php every 30 mins with wget:
01,30 * * * * /usr/bin/wget -q "http://www.your-domain-url.com/wp-cron.php?doing_wp_cron"
Invoke the wp-cron.php less frequently, saves the server from processing the wp-cron.php thousands of useless times.
Altering the way wp-cron.php works should be seen immediately as the reduced server load should drop a bit.
Consider you might need to play with the script exec frequency until you get, best fit cron timing. For my company case there are only up to 3 new article posted a week, hence too high frequence of wp-cron.php invocations is useless.
With blog where new posts occur once a day a script schedule frequency of 6 up to 12 hours should be ok.
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