Make the variable system more robust

Subscribe. variable_init() now variable_initialize() in Drupal 7.

This needs to put up a maintenance page with a nice message.

webchick asked for more hand holding here.Wrap the first if in a try-catch to make sure no exceptions are thrown when reading from the database or from cache. After that, check that the install_time variable is set -- given that's set by install.php it always will be set. If not then it's time to put up a maint page with a nice error message and leave.

  drupal_maintenance_theme()
  print theme('maintenance_page', array('content' => t('boo.')));
  exit;

Not sure what your definition of 'Novice' is, but by my definition, a novice would have no idea what to do here. So at risk of sounding like a complete novice myself, I ask that for a novice issue, please recommend at least a module to look at, if not an actual line number.

variable_init() looks like what?

D6: http://api.drupal.org/api/function/variable_init/6
D7: http://api.drupal.org/api/function/variable_initialize/7

Q: Where in the function is the problem?
A: The functions differ from D6 to D7 so there is an extra determination that must be made.
D6:

function variable_init($conf = array()) {
  // NOTE: caching the variables improves performance by 20% when serving cached pages.
  if ($cached = cache_get('variables', 'cache')) {
    $variables = $cached->data;
  }
  else {
    $result = db_query('SELECT * FROM {variable}');
    while ($variable = db_fetch_object($result)) {
      $variables[$variable->name] = unserialize($variable->value);
    }
    cache_set('variables', $variables);
  }

  foreach ($conf as $name => $value) {
    $variables[$name] = $value;
  }

  return $variables;
}

The error here is that it is assumed that the ...

D7:

function variable_initialize($conf = array()) {
  // NOTE: caching the variables improves performance by 20% when serving cached pages.
  if ($cached = cache_get('variables', 'cache_bootstrap')) {
    $variables = $cached->data;
  }
  else {
    $variables = array_map('unserialize', db_query('SELECT name, value FROM {variable}')->fetchAllKeyed());
    cache_set('variables', $variables, 'cache_bootstrap');
  }

  foreach ($conf as $name => $value) {
    $variables[$name] = $value;
  }

  return $variables;
}

The error here is...

Q: Where do I need to put a redirect to the maintenance page?

Q:How do I redirect to a maintenance page?

Q:How do I give the maintenance page a nice message?

Q:What are acceptable messages to give?

Sorry if this sounds just bothersome and inconsequential to you, but a novice would really have no idea and would most likely be asking these questions. I don't consider myself a novice, but I when it comes to D7 core, I must be since I am asking these questions. Though, a true 'novice' might not even know where to find these functions... not trying to be controversial, just encouraging you to keep it in perspective is all. And maybe tag with 'Intermediate' if a 'Novice' could not figure this out from the given information.

Interesting, so subscribing.

I think sirkitree crossposted with me. The variable_initialize is in bootstrap.inc and short of writing the code myself I gave as much instructions I could, I think. There is no need to redirect -- you need to print a maint page. What message to give, well figure out one, that's a challenge yes but not insurmountable.

I'm not sure this is as simple as it first seems.

I tried changing the function to

function variable_initialize($conf = array()) {
  // NOTE: caching the variables improves performance by 20% when serving cached pages.
  if ($cached = cache_get('variables', 'cache_bootstrap')) {
    $variables = $cached->data;
  }
  else {
    $variables = array_map('unserialize', db_query('SELECT name, value FROM {variable}')->fetchAllKeyed());
    cache_set('variables', $variables, 'cache_bootstrap');
  }

  if (count($variables) == 0){
    drupal_set_title(t('Site unavailable'));
    print theme('maintenance_page', array('content' => 'Drupal variables have failed to initialize', 'show_messages' => FALSE));
    exit;
  }

  foreach ($conf as $name => $value) {
    $variables[$name] = $value;
  }


  return $variables;
}

This doesn't work as the function is called at this point in the bootstrap process the theme layer is not available. There does not appear to be a standard way of presenting an error page before the theme layer is loaded - is there?

Haha... that's why drupal_maintenance_theme() exists!!! Cross-posting strikes again...

@alexpott thanks for trying could you please read #4?

@chx

So I slotted this into the function...

  drupal_maintenance_theme();
  drupal_add_http_header('503 Service unavailable');
  drupal_set_title(t('Site unavailable'));
  print theme('maintenance_page', array('content' => t('Testing')));
  exit;

just before the return... and I'm getting the white screen of death... which seems to be due to the theme_registry not loading correctly as this is returning nothing theme('maintenance_page', array('content' => t('Testing')))... with a few debug prints the theme function is returning nothing because theme_maintenance_page isn't set in $hooks:

  if (!isset($hooks[$hook])) {
    watchdog('theme', 'Theme key "@key" not found.', array('@key' => $hook), WATCHDOG_WARNING);
    return '';
  }

I'm trying to investigate this further...

That will teach me what do I call novice... drupal_maintenance_theme does not behave as it should since the database is active.

This still needs a nice message and likely other polish but it will get you going.

Used the same message as produced by _drupal_log_error() [in common.inc] as this message will be displayed any visitor to the site if the error occurs. The error will also generate a 503 http response with a retry time of 3 to indicate the site is temporarily unavailable.

The message is The website encountered an unexpected error. Please try again later.

Additionally, chx's original patch broke drupal installing as $variables is empty during an install so I've added a check on the global MAINTENANCE_MODE

Here's a patch to generate a service unavailable based on the apache server 503 text and looking somewhat like Damien's guru mediation page.

There are a couple of things I don't like about this patch - it's not using the maintenance theme, it's putting html into bootstrap.inc, it's not translateable. However, because this is an edge case and will happen before Drupal is fully bootstrapped perhaps this is acceptable? It does have an advantage over using the maintenance theme because it is generating a 503 status rather a 500 which indicates the error is temporary.

Apparently, I can't remove a tag without adding a comment. But I'm removing the "Novice" tag all the same.

Last patch does not apply, so setting to 'needs work'.