mxqsub: Implement per user limits

This patch implements two limits:

1) The number of active groups per user (default: 100)
2) The number of pending jobs per group (default: 10000)

The limits can be changed at compile time e.g.

    EXTRA_CFLAGS="$EXTRA_CFLAGS -DMXQ_MAX_ACTIVE_GROUPS_PER_USER=200"
    EXTRA_CFLAGS="$EXTRA_CFLAGS -DMXQ_MAX_PENDING_JOBS_PER_GROUP=20000"
    make install EXTRA_CFLAGS="$EXTRA_CFLAGS"

mxsub will abort with an error message if adding a further job would
exceed a limit. E.g.:

    ERROR: Limit of 10000 pending jobs per group reached for group_id 20

    ERROR: Limit of 100 active groups reached for user buczek

An active group is a group with pending (inq) or running jobs.

mxq.h

@@ -52,6 +52,14 @@
 #   define MXQ_LOGDIR "/var/log"
 #endif
 
+#ifndef MXQ_MAX_ACTIVE_GROUPS_PER_USER
+#   define MXQ_MAX_ACTIVE_GROUPS_PER_USER 100
+#endif
+
+#ifndef MXQ_MAX_PENDING_JOBS_PER_GROUP
+#   define MXQ_MAX_PENDING_JOBS_PER_GROUP 10000
+#endif
+
 static void mxq_print_generic_version(void)
 {
     printf(

mxqsub.c

@@ -152,7 +152,8 @@ static int load_group_id(struct mx_mysql *mysql, struct mxq_group *g)
 
     stmt = mx_mysql_statement_prepare(mysql,
             "SELECT"
-                " group_id"
+                " group_id,"
+                " group_jobs_inq"
             " FROM mxq_group "
             " WHERE group_name = ?"
                 " AND user_uid = ?"
@@ -198,6 +199,7 @@ static int load_group_id(struct mx_mysql *mysql, struct mxq_group *g)
 
     if (num_rows) {
         mx_mysql_statement_result_bind(stmt, 0, uint64, &(g->group_id));
+        mx_mysql_statement_result_bind(stmt, 1, uint64, &(g->group_jobs_inq));
 
         res = mx_mysql_statement_fetch(stmt);
         if (res < 0) {
@@ -513,6 +515,43 @@ static int add_job(struct mx_mysql *mysql, struct mxq_job *j)
     return (int)num_rows;
 }
 
+static int get_active_groups_for_user(struct mx_mysql *mysql, char *username)
+{
+    struct mx_mysql_stmt *stmt;
+    int res;
+    unsigned long long num_rows;
+    uint64_t count;
+
+    stmt = mx_mysql_statement_prepare(mysql,
+            "SELECT"
+                " count(*)"
+            " FROM mxq_group"
+            " WHERE user_name = ?"
+              " AND (group_jobs_inq > 0 OR group_jobs_running > 0)");
+    if (!stmt) {
+        mx_log_err("mx_mysql_statement_prepare(): %m");
+        return -errno;
+    }
+    mx_mysql_statement_param_bind(stmt, 0, string, &username);
+    res = mx_mysql_statement_execute(stmt, &num_rows);
+    if (res < 0) {
+        mx_log_err("mx_mysql_statement_execute(): %m");
+        mx_mysql_statement_close(&stmt);
+        return res;
+    }
+    assert(num_rows == 1);
+    mx_mysql_statement_result_bind(stmt, 0, uint64, &count);
+    res = mx_mysql_statement_fetch(stmt);
+    if (res < 0) {
+        mx_log_err("mx_mysql_statement_fetch(): %m");
+        mx_mysql_statement_close(&stmt);
+        return res;
+    }
+    mx_mysql_statement_close(&stmt);
+    assert(count<INT_MAX);
+    return count;
+}
+
 static int mxq_submit_task(struct mx_mysql *mysql, struct mxq_job *j, int flags, uint64_t group_id)
 {
     int res;
@@ -537,6 +576,10 @@ static int mxq_submit_task(struct mx_mysql *mysql, struct mxq_job *j, int flags,
         return res;
 
     if (res == 0) {
+        if (get_active_groups_for_user(mysql,g->user_name)>=MXQ_MAX_ACTIVE_GROUPS_PER_USER) {
+            mx_log_err("Limit of %d active groups reached for user %s",MXQ_MAX_ACTIVE_GROUPS_PER_USER,g->user_name);
+            return -(errno=EDQUOT);
+        }
         res = add_group(mysql, g);
         if (res < 0)
             return res;
@@ -549,6 +592,11 @@ static int mxq_submit_task(struct mx_mysql *mysql, struct mxq_job *j, int flags,
         mx_log_info("The new job will be added to new group with group_id=%lu", g->group_id);
 
     } else {
+        mx_log_debug("pending: %lu",g->group_jobs_inq);
+        if (g->group_jobs_inq >= MXQ_MAX_PENDING_JOBS_PER_GROUP) {
+            mx_log_err("Limit of %d pending jobs per group reached for group_id %lu",MXQ_MAX_PENDING_JOBS_PER_GROUP,g->group_id);
+            return -(errno=EDQUOT);
+        }
         mx_log_info("The new job will be attached to existing group with group_id=%lu", g->group_id);
     }
 
@@ -999,7 +1047,7 @@ int main(int argc, char *argv[])
     mx_log_info("MySQL: Connection to database closed.");
 
     if (res < 0) {
-        if (res != -ENOENT)
+        if (res != -ENOENT && res != -EDQUOT)
             mx_log_err("Job submission failed: %m");
         return 1;
     }