Adding upstream version 2.1.6.upstream/2.1.6

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 86 insertions, 0 deletions

diff --git a/include/crm/cluster/election_internal.h b/include/crm/cluster/election_internal.h
new file mode 100644
index 0000000..665c3a0
--- /dev/null
+++ b/include/crm/cluster/election_internal.h
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2009-2022 the Pacemaker project contributors
+ *
+ * The version control history for this file may have further details.
+ *
+ * This source code is licensed under the GNU Lesser General Public License
+ * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
+ */
+
+#ifndef CRM_COMMON_ELECTION__H
+#  define CRM_COMMON_ELECTION__H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \file
+ * \brief Functions for conducting elections
+ *
+ * An election is useful for a daemon that runs on all nodes but needs any one
+ * instance to perform a special role.
+ *
+ * Elections are closely tied to the cluster peer cache. Peers in the cache that
+ * are active members are eligible to vote. Elections are named for logging
+ * purposes, but only one election may exist at any time, so typically an
+ * election would be created at daemon start-up and freed at shutdown.
+ *
+ * Pacemaker's election procedure has been heavily adapted from the
+ * Invitation Algorithm variant of the Garcia-Molina Bully Algorithm:
+ *
+ *   https://en.wikipedia.org/wiki/Bully_algorithm
+ *
+ * Elections are conducted via cluster messages. There are two types of
+ * messages: a "vote" is a declaration of the voting node's candidacy, and is
+ * always broadcast; a "no-vote" is a concession by the responding node, and is
+ * always a reply to the preferred node's vote. (These correspond to "invite"
+ * and "accept" in the traditional algorithm.)
+ *
+ * A vote together with any no-vote replies to it is considered an election
+ * round. Rounds are numbered with a simple counter unique to each node
+ * (this would be the group number in the traditional algorithm). Concurrent
+ * election rounds are possible.
+ *
+ * An election round is started when any node broadcasts a vote. When a node
+ * receives another node's vote, it compares itself against the sending node
+ * according to certain metrics, and either starts a new round (if it prefers
+ * itself) or replies to the other node with a no-vote (if it prefers that
+ * node).
+ *
+ * If a node receives no-votes from all other active nodes, it declares itself
+ * the winner. The library API does not notify other nodes of this; callers
+ * must implement that if desired.
+ */
+
+typedef struct election_s election_t;
+
+/*! Possible election states */
+enum election_result {
+    election_start = 0,     /*! new election needed */
+    election_in_progress,   /*! election started but not all peers have voted */
+    election_lost,          /*! local node lost most recent election */
+    election_won,           /*! local node won most recent election */
+    election_error,         /*! election message or election object invalid */
+};
+
+void election_fini(election_t *e);
+void election_reset(election_t *e);
+election_t *election_init(const char *name, const char *uname, guint period_ms, GSourceFunc cb);
+
+void election_timeout_set_period(election_t *e, guint period_ms);
+void election_timeout_stop(election_t *e);
+
+void election_vote(election_t *e);
+bool election_check(election_t *e);
+void election_remove(election_t *e, const char *uname);
+enum election_result election_state(const election_t *e);
+enum election_result election_count_vote(election_t *e, const xmlNode *message,
+                                         bool can_win);
+void election_clear_dampening(election_t *e);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif