postgresql plugin: Unregister all writers on shutdown.

This will make sure that all pending transactions will be committed. Else, the
open transactions would be rolled back by the PostgreSQL backend when closing
the connection.

In order to do so, all database connections are now stored in a plugin-global
array (this will also make further changes possible). Also, a ref-count has
been added to the database object in order to support "deleting" an object
twice when having it in use by a connection doing queries and writes.

diff --git a/src/postgresql.c b/src/postgresql.c
index 4d9fc56..4d24360 100644 (file)
--- a/src/postgresql.c
+++ b/src/postgresql.c
@@ -152,6 +152,8 @@ typedef struct {
        char *krbsrvname;
 
        char *service;
+
+       int ref_cnt;
 } c_psql_database_t;
 
 static char *def_queries[] = {
@@ -165,6 +167,9 @@ static char *def_queries[] = {
 };
 static int def_queries_num = STATIC_ARRAY_SIZE (def_queries);
 
+static c_psql_database_t *databases     = NULL;
+static size_t             databases_num = 0;
+
 static udb_query_t      **queries       = NULL;
 static size_t             queries_num   = 0;
 
@@ -214,12 +219,17 @@ static c_psql_database_t *c_psql_database_new (const char *name)
 {
        c_psql_database_t *db;
 
-       db = (c_psql_database_t *)malloc (sizeof (*db));
+       db = (c_psql_database_t *)realloc (databases,
+                       (databases_num + 1) * sizeof (*db));
        if (NULL == db) {
                log_err ("Out of memory.");
                return NULL;
        }
 
+       databases = db;
+       db = databases + databases_num;
+       ++databases_num;
+
        db->conn = NULL;
 
        C_COMPLAIN_INIT (&db->conn_complaint);
@@ -254,6 +264,8 @@ static c_psql_database_t *c_psql_database_new (const char *name)
        db->krbsrvname = NULL;
 
        db->service    = NULL;
+
+       db->ref_cnt    = 0;
        return db;
 } /* c_psql_database_new */
 
@@ -263,6 +275,11 @@ static void c_psql_database_delete (void *data)
 
        c_psql_database_t *db = data;
 
+       --db->ref_cnt;
+       /* readers and writers may access this database */
+       if (db->ref_cnt > 0)
+               return;
+
        /* wait for the lock to be released by the last writer */
        pthread_mutex_lock (&db->db_lock);
 
@@ -298,6 +315,9 @@ static void c_psql_database_delete (void *data)
        sfree (db->krbsrvname);
 
        sfree (db->service);
+
+       /* don't care about freeing or reordering the 'databases' array
+        * this is done in 'shutdown' */
        return;
 } /* c_psql_database_delete */
 
@@ -308,7 +328,7 @@ static int c_psql_connect (c_psql_database_t *db)
        int   buf_len = sizeof (conninfo);
        int   status;
 
-       if (! db)
+       if ((! db) || (! db->database))
                return -1;
 
        status = ssnprintf (buf, buf_len, "dbname = '%s'", db->database);
@@ -916,8 +936,23 @@ static int c_psql_write (const data_set_t *ds, const value_list_t *vl,
 
 static int c_psql_shutdown (void)
 {
+       size_t i = 0;
+
        plugin_unregister_read_group ("postgresql");
 
+       for (i = 0; i < databases_num; ++i) {
+               c_psql_database_t *db = databases + i;
+               size_t j = 0;
+
+               for (j = 0; j < db->writers_num; ++j) {
+                       char cb_name[DATA_MAX_NAME_LEN];
+
+                       ssnprintf (cb_name, sizeof (cb_name), "postgresql-%s",
+                                       db->database);
+                       plugin_unregister_write (cb_name);
+               }
+       }
+
        udb_query_free (queries, queries_num);
        queries = NULL;
        queries_num = 0;
@@ -926,6 +961,10 @@ static int c_psql_shutdown (void)
        writers = NULL;
        writers_num = 0;
 
+       sfree (databases);
+       databases = NULL;
+       databases_num = 0;
+
        return 0;
 } /* c_psql_shutdown */
 
@@ -1178,11 +1217,13 @@ static int c_psql_config_database (oconfig_item_t *ci)
        if (db->queries_num > 0) {
                CDTIME_T_TO_TIMESPEC (db->interval, &cb_interval);
 
+               ++db->ref_cnt;
                plugin_register_complex_read ("postgresql", cb_name, c_psql_read,
                                /* interval = */ (db->interval > 0) ? &cb_interval : NULL,
                                &ud);
        }
        if (db->writers_num > 0) {
+               ++db->ref_cnt;
                plugin_register_write (cb_name, c_psql_write, &ud);
        }
        else if (db->commit_interval > 0) {