Multcasting - Hosts Do Not Contain the Same Image Assignments

[Wayne Workman]

Moved to bug reports.

[jgurka]

@Tom-Elliott

This was on a CentOS 7 Hyper-V installation using 6120. The issue still persists in 6124, but appears to be a minor issue with the PHP from the 6018 revision of the doMembersHaveUniformImages function within group.class.php:

After changing it back to the previous version (5527) of the function:

I haven’t had a chance to test it out, but my guess is that multicast is going to work now. I’ll update in the AM.

[Wayne Workman]

@jgurka Hey that’s great work, awesome.

[jgurka]

@Wayne-Workman & @Tom-Elliott

I had a chance to test out my configuration yesterday and it seemed to be working AOK. Now I’m just working on getting all of the FOG services to play nice with systemd and the nfs services at boot up.

I saw Tom changed “array_sum” to “array_count_values” in one of his commits yesterday, but unfortunately that does not resolve the issue. I’m by no means a dev, but from the logic I see it’s always going to return a false value due to the second half of the validation:

... && $images[0] == $this->getHostCount());

$images should be counting and outputting the number of hosts in the group (let’s say $images=2). The $images[0] would be # hosts + 1 (so 2+1=3) resulting in there always being an output of one value greater than the number of hosts being pulled from GetHostCount().

Since you can’t use a decrementing operator on an array, I’d assume you need to create another array to then subtract from $images.

Maybe there is another way for you to validate number of hosts counted in $images and getHostCount() that would be easier. As a temporary fix, I’ve just been removing the second half of the validation so it’ll return true and allow me to create the task.

Hope that helps!

[Tom Elliott]

@jgurka
I don’t know what you mean.

If i count the values returned, the value should be the same as the count of hosts within the group.

[Hanz]

@Tom-Elliott I just messaged you that SVN 6138 is still throwing this error

[jgurka]

@Tom-Elliott

I’m not well-versed at all in OOP, but from what I understand, the way you had it setup was that it was taking the highest key in the output array and then adding one onto the value. Apparently that’s how PHP interprets it.

Your latest code, as noted by Hanz, is still broken. I was able to alter your previous version of group.class.php (6128) to get both pieces of the validation working properly (at least it appears):

    public function doMembersHaveUniformImages() {
        $images = array_count_values($this->getSubObjectIDs('Host',array('id'=>$this->get('hosts')),'imageID'));
        return (count($images) == 1 && count($images['Host'] == $this->getHostCount()));

-JG

[Tom Elliott]

@jgurka I’m not understanding at all.

I can take a look more definitively about the code, but the lines you reference are comparison’s not add/remove/etc…

So:

... && $images[0] == $this->getHostCount());

From before is compariing if the value in array [0] of variable $images is equal to the value returned by $this->getHostCount().

Theres no adding 1 to it or anything.

[Wayne Workman]

@jgurka Can you please pull down the latest via GIT and make your changes to the source, and then do a commit and push and then a pull requesT?

[Tom Elliott]

@jgurka In regards to this:

$images[‘Host’] doesn’t exist.

return (count($images) ==1) works, but the problem with this is it isn’t counting the values and matching it to all the hosts in the group.

Why?

Because count($images) == 1 will return true if only a single host in the group has an image where all the others do not.

[Tom Elliott]

My revised code: explained if you need to understand a bit more.

    public function doMembersHaveUniformImages() {
        $imageID = $this->getSubObjectIDs('Host',array('id'=>$this->get('hosts')),'imageID','','', '','','array_count_values');
        return (count($imageID) == 1 && $imageID[0] == $this->getHostCount());
    }

First, we get all the counts of the values returned. This return will store in an array, not an associative array. Meaning values in this will be:

imageID[0]
imageID[1]
imageID[2]

etc…

the return will count the total number of items in the array,

if it’s 0, or greater than 1, we know they aren’t uniform.

If it is one, the count should match that of the number of hosts in the group.

If that doesn’t match, we know they aren’t uniform.

If both tests pass, we know they are uniform.

Does this help?

[jgurka]

@Tom-Elliott

This is how I understand it:

$images = array_count_values…

• Outputs an array of the counts for each item listed.
  • E.g., Host = 2, imageID = 1

$images[0]

• References the output array and will take the maximum of existing integer indices as the value.
  • If Host = 2 and imageID = 1, PHP would be taking a value of 2.
• [0] specifies the key value. Since PHP starts counting at 0 for integers, the value 0 is actually equal to “maximum of existing integer + 1.”
• So, if $images pulled value of 2 and we add [0], it’s actually doing “2+1=3.”

[Tom Elliott]

@jgurka What you’re saying is wrong. I coded it, I know what it’s doing. I’m trying to help.

[Tom Elliott]

Further,

Array count values, doesn’t matter how it gets the informatin, it’s only counting the values.

for example:

this[0] = 1
this[1] = 1
this[2] = 2

Array count values on it will return:

this[1] => 2
this[2] => 1

So i do have an error: but the error is not the way you’re seeing it.

[Tom Elliott]

Hopefully this one works:

    public function doMembersHaveUniformImages() {
        $imageID = $this->getSubObjectIDs('Host',array('id'=>$this->get('hosts')),'imageID','','', '','','array_count_values');
        $imageID = count($imageID) == 1 ? array_shift($imageID) : 0;
        return $imageID == $this->getHostCount();
    }

[jgurka]

@Tom-Elliott

‘Host’ is defined in the output array for $images?

PHP.net reference on array_count_values

• array_count_values() returns an array using the values of array as keys and their frequency in array as values.

This shows an example output at bottom of page for array_count_values

Btw, I’m not trying to attack you at all.

[Tom Elliott]

@jgurka You’re reading it incorrectly though.

Understand, I’m not trying to attack either.

I’m not passing anything with a value of Host.

THe “getSubObjectIDs” is only getting the id’s of an object. So, without the array_count_values, it returns only the id’s of the manager and field it is requesting. (in this case the imageID field).

So it will receiving the values in non associative form:

eg.

$imageID[0] = 15 (15 here is the image id returned.)
$imageID[1] = 16 (16 here is the image id returned.)

It then passes (if array_count_values) is passed, through that and returns:

imageID[15] = 1 (here the array key is swapped from a normal associative array to whatever the value was, and the number is the total count of the 15 values, so from above it is only 1 count.)

[jgurka]

@Tom-Elliott

I’m doing my best to follow your explanation. Please note I’ve been referring to the older version that I edited and not your latest (I’ll spin up a VM in a little to see if it’s working).

Let me see if I’m following correctly. I’m referencing the older version of the code:

    public function doMembersHaveUniformImages() {
        $images = array_count_values($this->getSubObjectIDs('Host',array('id'=>$this->get('hosts')),'imageID'));
        return (count($images) == 1 && $images[0] == $this->getHostCount());

$images defines the new array & equals sets that variable to the output of what follows.

array_count_values will count all of the values that are output from what follows.

$this is used to reference the calling object (in this case getSubObjectIDs) and -> points it to the object.

‘Host’ is referring to the class Host that is set by host.class.php

array(‘id’=>$this->get(‘hosts’) tells it to create an array, referencing ‘id’ that’s defined in group.class.php (database field ‘groupID’). $this references the call object of get(‘hosts’), which is defined within tasklog.class.php as returning the hosts listed in the ‘taskID.’

array_count_values($this->getSubObjectIDs(‘Host’,array(‘id’=>$this->get(‘hosts’)),‘imageID’) as a whole is telling it to get the subobject IDs from ‘Host’ following the condition that they have the same GroupIDs assigned and also the subobject ID(s) of imageID based on qualifying as same groupID. It is then counting the number of each subobject IDs that resulted for ‘hosts’ and ‘imageID.’

Note: I’m under the impression this would be outputting in a format like ([hosts] => 2 [imageID] =>1).

return specifies what follows as evaluating to either true or false.

count($images) is using the count function on array that was outputted from above.

Note: it appears that using count on an array like it is here will count the entire array as a whole, which is always going to result in an output of 1.

count($images) == 1 is a validation that the number of images being used is equal to one.

&& ties on an additional validation qualifier check

$images[0] is referencing the array output and setting the key to 0.

Note: from what I’ve been able to find, non-associative arrays automatically use the next integer value in the key sequence, starting at 0, for key if you do not provide one. Non-associative arrays also increment by 1 starting with the value 0, thus key 0 is adding a value 1 on. I’m understanding it as taking the value “2”, since it’s the largest of the two values in the output array and then incrementing it by one.

$images[0] == $this->getHostCount() is validating that the number of hosts found by $images array is equal to that found by the getHostCount() function specified in group.class.php

return (count($images) == 1 && $images[0] == $this->getHostCount()); as a whole this is validating that both the number of images is equal to one and that the number of hosts match and will return true if both are true or false if either fail.

Let me know your thoughts on my logic – I’m just interested in PHP after looking at this and want to better understand exactly what is occurring.

Thanks,
JG

[jgurka]

@Tom-Elliott

Just had a chance to try out your latest revision – working like a charm.

After writing all that up and re-reading your post, I get what you’re saying now. Really, all you’re doing is retrieving two sets of items:

1. ID of the manager
2. IDs of all images in the specified group

Since ‘Host’ isn’t included in the following array call (where array_count_values is now located), it is only counting the values that it pulled from imageID that are members of the group. It then counts up how many of each imageID there is (should only be one) and sets the variable equal to that.

I also see what you’re saying about $array[0] not being an actual array but the output number now that I can see that you’re really only interested in counting imageIDs – not multiple items like I thought.

Thanks for the explanation & fix!

[Hanz]

This post is deleted!