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MDEV-31400 Simple plugin dependency resolution
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We introduce simple plugin dependency. A plugin init function may
return HA_ERR_RETRY_INIT. If this happens during server startup when
the server is trying to initialise all plugins, the failed plugins
will be retried, until no more plugins succeed in initialisation or
want to be retried.

This will fix spider init bugs which is caused in part by its
dependency on Aria for initialisation.

The reason we need a new return code, instead of treating every
failure as a request for retry, is that it may be impossible to clean
up after a failed plugin initialisation. Take InnoDB for example, it
has a global variable `buf_page_cleaner_is_active`, which may not
satisfy an assertion during a second initialisation try, probably
because InnoDB does not expect the initialisation to be called
twice.
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@mariadb-YuchenPei
mariadb-YuchenPei committed Jul 25, 2023
1 parent 668eb2c commit 734583b
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Showing 3 changed files with 108 additions and 55 deletions.
1 change: 1 addition & 0 deletions include/my_base.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -442,6 +442,7 @@ enum ha_base_keytype {
#define HA_ERR_CRASHED 126 /* Indexfile is crashed */
#define HA_ERR_WRONG_IN_RECORD 127 /* Record-file is crashed */
#define HA_ERR_OUT_OF_MEM 128 /* Out of memory */
#define HA_ERR_RETRY_INIT 129 /* Initialization failed and should be retried */
#define HA_ERR_NOT_A_TABLE 130 /* not a MYI file - no signature */
#define HA_ERR_WRONG_COMMAND 131 /* Command not supported */
#define HA_ERR_OLD_FILE 132 /* old databasfile */
Expand Down
22 changes: 15 additions & 7 deletions sql/handler.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -550,6 +550,7 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
{
handlerton *hton;
static const char *no_exts[]= { 0 };
int ret= 0;
DBUG_ENTER("ha_initialize_handlerton");
DBUG_PRINT("plugin", ("initialize plugin: '%s'", plugin->name.str));

Expand All @@ -559,6 +560,7 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
{
sql_print_error("Unable to allocate memory for plugin '%s' handlerton.",
plugin->name.str);
ret= 1;
goto err_no_hton_memory;
}

Expand All @@ -568,12 +570,16 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
hton->slot= HA_SLOT_UNDEF;
/* Historical Requirement */
plugin->data= hton; // shortcut for the future
if (plugin->plugin->init && plugin->plugin->init(hton))
{
sql_print_error("Plugin '%s' init function returned error.",
plugin->name.str);
/* [remove after merge] notes on merge conflict (MDEV-31400):
10.5: 81cd93bbb81d75e7cf14dedede0c9ec0712ace68
10.6-10.11: 13ba00ff4933cfc1712676f323587504e453d1b5
11.0-11.2: 42f8be10f18163c4025710cf6a212e82bddb2f62
The 10.11->11.0 conflict is trivial, but the reference commit also
contains different non-conflict changes needs to be applied to 11.0
(and beyond).
*/
if (plugin->plugin->init && (ret= plugin->plugin->init(hton)))
goto err;
}

// hton_ext_based_table_discovery() works only when discovery
// is supported and the engine if file-based.
Expand Down Expand Up @@ -616,6 +622,7 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
if (idx == (int) DB_TYPE_DEFAULT)
{
sql_print_warning("Too many storage engines!");
ret= 1;
goto err_deinit;
}
if (hton->db_type != DB_TYPE_UNKNOWN)
Expand Down Expand Up @@ -643,6 +650,7 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
{
sql_print_error("Too many plugins loaded. Limit is %lu. "
"Failed on '%s'", (ulong) MAX_HA, plugin->name.str);
ret= 1;
goto err_deinit;
}
hton->slot= total_ha++;
Expand Down Expand Up @@ -699,7 +707,7 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
resolve_sysvar_table_options(hton);
update_discovery_counters(hton, 1);

DBUG_RETURN(0);
DBUG_RETURN(ret);

err_deinit:
/*
Expand All @@ -717,7 +725,7 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
my_free(hton);
err_no_hton_memory:
plugin->data= NULL;
DBUG_RETURN(1);
DBUG_RETURN(ret);
}

int ha_init()
Expand Down
140 changes: 92 additions & 48 deletions sql/sql_plugin.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1411,6 +1411,50 @@ void plugin_unlock_list(THD *thd, plugin_ref *list, uint count)
DBUG_VOID_RETURN;
}

static void print_init_failed_error(st_plugin_int *p)
{
sql_print_error("Plugin '%s' registration as a %s failed.",
p->name.str,
plugin_type_names[p->plugin->type].str);
}

static int plugin_do_initialize(struct st_plugin_int *plugin, uint &state)
{
DBUG_ENTER("plugin_do_initialize");
mysql_mutex_assert_not_owner(&LOCK_plugin);
plugin_type_init init= plugin_type_initialize[plugin->plugin->type];
if (!init)
init= (plugin_type_init) plugin->plugin->init;
if (init)
if (int ret= init(plugin))
{
/* Plugin init failed and did not requested a retry */
if (ret != HA_ERR_RETRY_INIT)
print_init_failed_error(plugin);
DBUG_RETURN(ret);
}
state= PLUGIN_IS_READY; // plugin->init() succeeded

if (plugin->plugin->status_vars)
{
/*
historical ndb behavior caused MySQL plugins to specify
status var names in full, with the plugin name prefix.
this was never fixed in MySQL.
MariaDB fixes that but supports MySQL style too.
*/
SHOW_VAR *show_vars= plugin->plugin->status_vars;
SHOW_VAR tmp_array[2]= {{plugin->plugin->name,
(char *) plugin->plugin->status_vars, SHOW_ARRAY},
{0, 0, SHOW_UNDEF}};
if (strncasecmp(show_vars->name, plugin->name.str, plugin->name.length))
show_vars= tmp_array;

if (add_status_vars(show_vars))
DBUG_RETURN(1);
}
DBUG_RETURN(0);
}

static int plugin_initialize(MEM_ROOT *tmp_root, struct st_plugin_int *plugin,
int *argc, char **argv, bool options_only)
Expand All @@ -1433,52 +1477,10 @@ static int plugin_initialize(MEM_ROOT *tmp_root, struct st_plugin_int *plugin,
{
ret= !options_only && plugin_is_forced(plugin);
state= PLUGIN_IS_DISABLED;
goto err;
}

if (plugin_type_initialize[plugin->plugin->type])
{
if ((*plugin_type_initialize[plugin->plugin->type])(plugin))
{
sql_print_error("Plugin '%s' registration as a %s failed.",
plugin->name.str, plugin_type_names[plugin->plugin->type].str);
goto err;
}
}
else if (plugin->plugin->init)
{
if (plugin->plugin->init(plugin))
{
sql_print_error("Plugin '%s' init function returned error.",
plugin->name.str);
goto err;
}
}
state= PLUGIN_IS_READY; // plugin->init() succeeded

if (plugin->plugin->status_vars)
{
/*
historical ndb behavior caused MySQL plugins to specify
status var names in full, with the plugin name prefix.
this was never fixed in MySQL.
MariaDB fixes that but supports MySQL style too.
*/
SHOW_VAR *show_vars= plugin->plugin->status_vars;
SHOW_VAR tmp_array[2]= {
{plugin->plugin->name, (char*)plugin->plugin->status_vars, SHOW_ARRAY},
{0, 0, SHOW_UNDEF}
};
if (strncasecmp(show_vars->name, plugin->name.str, plugin->name.length))
show_vars= tmp_array;

if (add_status_vars(show_vars))
goto err;
}

ret= 0;
else
ret= plugin_do_initialize(plugin, state);

err:
if (ret)
plugin_variables_deinit(plugin);

Expand Down Expand Up @@ -1557,7 +1559,7 @@ int plugin_init(int *argc, char **argv, int flags)
uint i;
struct st_maria_plugin **builtins;
struct st_maria_plugin *plugin;
struct st_plugin_int tmp, *plugin_ptr, **reap;
struct st_plugin_int tmp, *plugin_ptr, **reap, **retry_end, **retry_start;
MEM_ROOT tmp_root;
bool reaped_mandatory_plugin= false;
bool mandatory= true;
Expand Down Expand Up @@ -1707,11 +1709,16 @@ int plugin_init(int *argc, char **argv, int flags)
*/

mysql_mutex_lock(&LOCK_plugin);
/* List of plugins to reap */
reap= (st_plugin_int **) my_alloca((plugin_array.elements+1) * sizeof(void*));
*(reap++)= NULL;
/* List of plugins to retry */
retry_start= retry_end=
(st_plugin_int **) my_alloca((plugin_array.elements+1) * sizeof(void*));

for(;;)
{
int error;
for (i=0; i < MYSQL_MAX_PLUGIN_TYPE_NUM; i++)
{
HASH *hash= plugin_hash + plugin_type_initialization_order[i];
Expand All @@ -1720,15 +1727,51 @@ int plugin_init(int *argc, char **argv, int flags)
plugin_ptr= (struct st_plugin_int *) my_hash_element(hash, idx);
if (plugin_ptr->state == PLUGIN_IS_UNINITIALIZED)
{
if (plugin_initialize(&tmp_root, plugin_ptr, argc, argv,
(flags & PLUGIN_INIT_SKIP_INITIALIZATION)))
error= plugin_initialize(&tmp_root, plugin_ptr, argc, argv,
(flags & PLUGIN_INIT_SKIP_INITIALIZATION));
if (error)
{
plugin_ptr->state= PLUGIN_IS_DYING;
*(reap++)= plugin_ptr;
/* The plugin wants a retry of the initialisation,
possibly due to dependency on other plugins */
if (unlikely(error == HA_ERR_RETRY_INIT))
*(retry_end++)= plugin_ptr;
else
*(reap++)= plugin_ptr;
}
}
}
}
/* Retry plugins that asked for it */
while (retry_start < retry_end)
{
st_plugin_int **to_re_retry, **retrying;
for (to_re_retry= retrying= retry_start; retrying < retry_end; retrying++)
{
plugin_ptr= *retrying;
uint state= plugin_ptr->state;
mysql_mutex_unlock(&LOCK_plugin);
error= plugin_do_initialize(plugin_ptr, state);
mysql_mutex_lock(&LOCK_plugin);
plugin_ptr->state= state;
if (error == HA_ERR_RETRY_INIT)
*(to_re_retry++)= plugin_ptr;
else if (error)
*(reap++)= plugin_ptr;
}
/* If the retry list has not changed, i.e. if all retry attempts
result in another retry request, empty the retry list */
if (to_re_retry == retry_end)
while (to_re_retry > retry_start)
{
plugin_ptr= *(--to_re_retry);
*(reap++)= plugin_ptr;
/** `plugin_do_initialize()' did not print any error in this
case, so we do it here. */
print_init_failed_error(plugin_ptr);
}
retry_end= to_re_retry;
}

/* load and init plugins from the plugin table (unless done already) */
if (flags & PLUGIN_INIT_SKIP_PLUGIN_TABLE)
Expand All @@ -1754,6 +1797,7 @@ int plugin_init(int *argc, char **argv, int flags)
}

mysql_mutex_unlock(&LOCK_plugin);
my_afree(retry_start);
my_afree(reap);
if (reaped_mandatory_plugin)
goto err;
Expand Down

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