Allow plugin execution order to be defined

This patch adds support for assigning a precedence to each plugin.
This precedence value is used to determine what order the plugins
should be called in within a given plugin type.

The precedence value is an integer between 1 and 99.  The value is
set in the nsslapd-pluginPrecedence attribute in a plugin config
entry in "cn=config".  If a plugin does not have a precedence
value set, the plugin is treated as if it has a precedence of 50.

For more details, see the feature design document at:

    http://directory.fedoraproject.org/wiki/Plugin_Ordering

I also removed an incorrect log message in the linked attrs plugin
that I noticed while debugging this patch.

1 files changed, 90 insertions, 2 deletions

diff --git a/ldap/servers/slapd/plugin.c b/ldap/servers/slapd/plugin.c
index 75ec4f92..1664cc16 100644
--- a/ldap/servers/slapd/plugin.c
+++ b/ldap/servers/slapd/plugin.c
@@ -105,11 +105,43 @@ static void
 add_plugin_to_list(struct slapdplugin **list, struct slapdplugin *plugin)
 {
 	struct slapdplugin **tmp;
+	struct slapdplugin *last = NULL;
+	int plugin_added = 0;
+
+	/* Insert the plugin into list based off of precedence. */
 	for ( tmp = list; *tmp; tmp = &(*tmp)->plg_next )
 	{
-	  ;	/* NULL */
+		if (plugin->plg_precedence < (*tmp)->plg_precedence)
+		{
+			if (last)
+			{
+				/* Insert item between last and tmp. */
+				plugin->plg_next = *tmp;
+				last->plg_next = plugin;
+			} else {
+				/* Add as the first list item. */
+				plugin->plg_next = *tmp;
+				*list = plugin;
+			}
+
+			plugin_added = 1;
+
+			/* We've added the plug-in to the
+ 			 * list, so bail from the loop. */
+			break;
+		}
+
+		/* Save a pointer to this plugin so we can
+		 * refer to it on the next loop iteration. */
+		last = *tmp;
+	}
+
+	/* If we didn't add the plug-in to the list yet,
+	 * it needs to be added to the end of the list. */
+	if (!plugin_added)
+	{
+		*tmp = plugin;
 	}
-	*tmp = plugin;
 }
 
 struct slapdplugin *
@@ -2024,6 +2056,37 @@ plugin_setup(Slapi_Entry *plugin_entry, struct slapi_componentid *group,
 		plugin->plg_name = value; /* plugin owns value's memory now, don't free */
 	}
 
+	if (!(value = slapi_entry_attr_get_charptr(plugin_entry, ATTR_PLUGIN_PRECEDENCE)))
+	{
+		/* A precedence isn't set, so just use the default. */
+		plugin->plg_precedence = PLUGIN_DEFAULT_PRECEDENCE;
+	}
+	else
+	{
+		/* A precedence was set, so let's make sure it's valid. */
+		int precedence = 0;
+		char *endptr = NULL;
+
+		/* Convert the value. */
+		precedence = strtol(value, &endptr, 10);
+
+		/* Make sure the precedence is within our valid
+		 * range and that we had no conversion errors. */
+		if ((*value == '\0') || (*endptr != '\0') ||
+			(precedence < PLUGIN_MIN_PRECEDENCE) || (precedence > PLUGIN_MAX_PRECEDENCE))
+		{
+			LDAPDebug(LDAP_DEBUG_ANY, "Error: value for attribute %s must be "
+				"an integer between %d and %d\n", ATTR_PLUGIN_PRECEDENCE,
+				PLUGIN_MIN_PRECEDENCE, PLUGIN_MAX_PRECEDENCE);
+			status = -1;
+			goto PLUGIN_CLEANUP;
+		}
+		else
+		{
+			plugin->plg_precedence = precedence;
+		}
+	}
+
 	if (!(value = slapi_entry_attr_get_charptr(plugin_entry,
 											   ATTR_PLUGIN_INITFN)))
 	{
@@ -2797,6 +2860,31 @@ void plugin_print_versions(void)
 }
 
 /*
+ * Prints a list of plugins in execution order for each
+ * plug-in type.  This will only be printed at the
+ * SLAPI_LOG_PLUGIN log level.
+ */
+void plugin_print_lists(void)
+{
+	int i;
+	struct slapdplugin *list = NULL;
+	struct slapdplugin *tmp = NULL;
+
+	for (i = 0; i < PLUGIN_LIST_GLOBAL_MAX; i++) {
+		if (list = get_plugin_list(i))
+		{
+			slapi_log_error(SLAPI_LOG_PLUGIN, NULL,
+				"---- Plugin List (type %d) ----\n", i);
+			for ( tmp = list; tmp; tmp = tmp->plg_next )
+			{
+				slapi_log_error(SLAPI_LOG_PLUGIN, NULL, "  %s (precedence: %d)\n",
+					tmp->plg_name, tmp->plg_precedence);
+			}
+		}
+	}
+}
+
+/*
  * check the spedified plugin entry and its nssladp-pluginEnabled value
  * Return Value: 1 if the plugin is on.
  *             : 0 otherwise.