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Longview App for Apache

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Longview for Apache is a Longview App. The Longview Apache tab appears in the Linode Manager when Longview detects that you have Apache installed on your Linode. With the Longview Apache App, you’ll be able to view statistics for Apache on your Linode. It can help you keep track of Apache’s settings, workers and requests, system resource consumption, and other information.

Installing

Prerequisites:

Debian and Ubuntu Automatic Configuration

If Apache is installed and running when you install the Longview client, the Apache App should enable and configure itself automatically.

If you already have Longview installed, and later want to install Apache and enable the Longview App for it, you can run Longview through its automatic configuration sequence again. In most cases, it will find everything it needs to get the Apache App started. And don’t worry - your old Longview data will stay safe. To run the automatic Longview configuration, first make sure that Apache is running, and then run the following command on your Linode via SSH:

dpkg-reconfigure -phigh linode-longview

For most people, Longview should be able to configure itself automatically, and you will receive output something like this:

  
    [ ok ] Stopping Longview Agent: longview.
    Checking Apache configuration...
    Found Apache status page at http://127.0.0.1/server-status?auto (default URL)
    [ ok ] Starting Longview Agent: longview.
    update-rc.d: using dependency based boot sequencing

Once you see this successful message, the Longview Apache App should automatically start collecting Apache data. Refresh the Longview Apache tab in the Linode Manager to start viewing your stats.

If you receive a failure message or the popup shown below, you should visit the Troubleshooting section at the end of this article.

Longview has detected Apache running on this server but was unable to access the server status page. Would you like to attempt to automatically configure mod\_status? This will require reloading Apache to enable. Autoconfigure Mod\_Status: \<Yes\> \<No\>

Manual Configuration (All Distributions)

To enable the Apache Longview app manually, follow these steps on your Linode via SSH:

  1. Make sure mod_status is enabled for Apache (it should be by default). You can follow the apache.org instructions at the link. Or, on Debian and Ubuntu systems, run this command:

    sudo a2enmod status

  2. Your httpd.conf file (or the file where you enabled mod_status; status.conf is another common location) should look like the following:

    httpd.conf 
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    <IfModule mod_status.c>
    ExtendedStatus On
    <Location /server-status>
        SetHandler server-status
        Require local
    </Location>
</IfModule>

  3. Edit /etc/linode/longview.d/Apache.conf to look like the following:

    /etc/linode/longview.d/Apache.conf 
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    location http://127.0.0.1/server-status?auto

  4. Restart Apache:

    Debian and Ubuntu:

    service apache2 restart

    CentOS and Fedora:

    apachectl restart

  5. Restart Longview:

    service longview restart

  6. Refresh the Longview Apache tab in the Linode Manager.

You should now be able to see Longview data for Apache. If that’s not the case, proceed to the Troubleshooting section at the end of this article.

Viewing Statistics

To see the output for the Longview Apache App:

  1. Log in to the Linode Manager.
  2. Select the Longview tab.
  3. Select the Apache tab.

Click the image for a full-size view.

The Longview Apache App.

You’ll see the current version of Apache listed on the upper right.

Mouse over a data point to see the exact numbers for that time. You can also zoom in on data points, or view older time periods with Longview Pro. For details, jump to this section in the main article about navigating the Longview interface. The next sections cover the Longview Apache App in detail.

Requests

The Requests graph shows the total number of requests Apache handled at the selected time. This is every HTTP and HTTPS request to your Linode.

Throughput

The Throughput graph shows the amount of data that Apache sent and received via web requests at the time selected.

Workers

The Workers graph shows all of the Apache workers at the selected time. The workers are broken down by state:

  • Waiting
  • Starting
  • Reading
  • Sending
  • Keepalive
  • DNS Lookup
  • Closing
  • Logging
  • Finishing
  • Cleanup

CPU

The CPU graph shows the percentage of your Linode’s CPU being used by Apache at the selected time. If you want to see the total CPU use instead, check the Overview tab.

Memory

The Memory graph shows the amount of RAM being used by Apache at the selected time. If you want to see your Linode’s total memory use instead, check the Overview tab.

Disk IO

The Disk IO graph shows the amount of input to and output from the disk caused by Apache at the selected time. To see the total IO instead, visit the Disks tab.

Process Count

The Process Count graph shows the total number of processes on your Linode spawned by Apache at the selected time. If you want to see more details, and how this stacks up against the total number of processes on your Linode, see the Process Explorer tab.

Troubleshooting

If you don’t see Longview data for Apache, you’ll instead get an error on the page and instructions on how to fix it. As a general tip, you can check the /var/log/linode/longview.log file for errors as well. You should also compare your mod_status configuration file (typically httpd.conf or status.conf) to the example shown in Step 2 of the Manual Configuration (All Distributions) section of this article.

By default Longview uses port 80 for its automatic configuration. In the event you are experiencing problems you may need to edit the /etc/apache2/ports.conf file to use port 8080 or another non-standard port.

Autoconfigure Mod_Status Popup

If you run the automatic Longview configuration tool, and get the popup message shown below:

Longview has detected Apache running on this server but was unable to access the server status page. Would you like to attempt to automatically configure mod\_status? This will require reloading Apache to enable. Autoconfigure Mod\_Status: \<Yes\> \<No\>

This indicates that Longview can’t locate the Apache status page. In turn, this could indicate that either:

  1. The status page is in an unusual and unspecified location.

  2. mod_status isn’t enabled.

  3. An Apache virtual host setting is interfering with requests to the status page.

  4. Apache itself is misconfigured.

If you choose:

  • <No>: the Longview tool will quit, and you can do a manual configuration. This is the safer option.

  • <Yes>: the Longview tool will attempt to enable mod_status, set the status page location, and restart Apache. This option is easier, but has the potential to disrupt your current Apache configuration. If you choose yes, and the configuration is successful, you should see output like the following:

      
        [ ok ] Stopping Longview Agent: longview.
        Checking Apache configuration...
        Enabling module status.
        To activate the new configuration, you need to run:
          service apache2 restart
        [....] Reloading web server config: . ok
        Apache mod_status enabled
        [ ok ] Starting Longview Agent: longview.
        update-rc.d: using dependency based boot sequencing

Refresh the Longview Apache tab in the Linode Manager to verify that it’s working now.

If instead you receive a failure message, such as:

  
    [FAIL] Reloading web server config: apache2 failed!

You will need to double-check your Apache installation, and then do a manual configuration.

Unable to Access Local Server Status for Apache

More specifically, the error will state Unable to access local server status for Apache at <http://example.com/example?auto>: <error>:. This error occurs when either:

  1. Apache’s mod_status setting is disabled or has been changed from the default location.

  2. An Apache virtual host configuration is interfering with web requests to the mod_status location.

Note
This error occurs when Longview attempts to check the status page location listed in /etc/linode/longview.d/Apache.conf, or the default page at 127.0.0.1/server-status?auto, but receives a non-200 HTTP response code. Basically, it means that the status page Longview is expecting is not being returned by the server.

To fix this, follow these steps:

  1. Make sure Apache is running:

    Debian and Ubuntu:

    service apache2 restart

    CentOS and Fedora:

    apachectl restart

  2. Make sure mod_status is enabled. See the Apache website for details. You can also check the output of the following command:

    apachectl -M | grep status

  3. Check the location for mod_status. The default location on Debian and Ubuntu systems is http://127.0.0.1/server-status?auto on localhost. In the Apache configuration file (typically httpd.conf or status.conf), this is designated with the lines:

    httpd.conf 
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    <Location /server-status>
    SetHandler server-status

    The SetHandler server-status line indicates that this is the location block for mod_status. The location line itself sets the location.

    On cPanel/WHM

    To direct Longview to the cPanel customized status page, edit the location line in /etc/linode/longview.d/Apache.conf to match the following:

    /etc/linode/longview.d/Apache.conf 
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    location http://localhost/whm-server-status?auto

  4. Longview is designed to check the default location automatically. If you use the default location shown above, you should be done. Refresh the Longview Apache tab in the Linode Manager to verify that it’s working now.

  5. If you’re not using the default location, you need to create a new file, /etc/linode/longview.d/Apache.conf, and set the location variable to match what you set in the Apache configuration file:

    /etc/linode/longview.d/Apache.conf 
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    location http://127.0.0.1/custom/location/path

  6. Determine if an Apache virtual host configuration is interfering with requests to the mod_status location. Use a tool like curl or wget to request the server status location:

    curl http://127.0.0.1/server-status?auto

    Observe the output. If the output looks like something other than a simple status page, then you’ll have to fix your Apache virtual host configuration.

  7. Restart Longview:

    service longview restart

  8. Refresh the Longview Apache tab in the Linode Manager to verify that it’s working now.

The Apache Status Page Doesn’t Look Right

More specifically, the error will state The Apache status page doesn't look right. Check <http://example.com/example?auto> and investigate any redirects for misconfiguration. This error occurs when Longview is able to reach the mod_status page, but doesn’t receive the expected content.

Note
This error occurs when Longview attempts to check the status page, and receives a 200 HTTP response code, but can’t scrape the expected status content from the page. That is, the page exists on your Linode, but it doesn’t have the right content. If, for example, Longview was to check your website’s home page, you would get this error.

To resolve this issue, follow these steps:

  1. Visit the URL shown in the error. See if it directs or redirects you to a page that isn’t the Apache status page.

  2. Update your Apache and Longview settings so that they specify the same location:

    • The <Location > line in httpd.conf or status.conf
    • The location line in /etc/linode/longview.d/Apache.conf

    If neither of these is set, the default location of http://127.0.0.1/server-status?auto on localhost will be used.

  3. Make sure there aren’t any Apache redirects or other settings that are affecting this page.

  4. Restart Longview:

    service longview restart

  5. Refresh the Longview Apache tab in the Linode Manager to verify that it’s working now.

Missing Graphs: Enable ExtendedStatus

If some of your Apache graphs are missing, you may see the error Enable ExtendedStatus in your Apache configuration for throughput and request graphs.

This indicates that you need to add the following line to your Apache configuration file (typically httpd.conf or status.conf) in the <IfModule mod_status.c> section:

httpd.conf 
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ExtendedStatus On

When you’ve finished modifying the configuration file, restart Apache:

Debian and Ubuntu:

service apache2 restart

CentOS and Fedora:

apachectl restart

Apache Tab is Missing

If the Longview Apache tab is missing entirely, this indicates that Apache is either not installed, or has stopped. If you restart Apache, you will be able to see the tab again and view all of your old data.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

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