diff --git a/lib/cluster/election.c b/lib/cluster/election.c index f7cd14d88b..a20d14dc24 100644 --- a/lib/cluster/election.c +++ b/lib/cluster/election.c @@ -1,719 +1,725 @@ /* - * Copyright 2004-2019 Andrew Beekhof + * Copyright 2004-2020 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. */ #include #include #include #include #include #include #include #include #include #define STORM_INTERVAL 2 /* in seconds */ struct election_s { enum election_result state; guint count; // How many times local node has voted char *name; // Descriptive name for this election char *uname; // Local node's name GSourceFunc cb; // Function to call if election is won GHashTable *voted; // Key = node name, value = how node voted mainloop_timer_t *timeout; // When to abort if all votes not received int election_wins; // Track wins, for storm detection bool wrote_blackbox; // Write a storm blackbox at most once time_t expires; // When storm detection period ends time_t last_election_loss; // When dampening period ends }; -static void election_complete(election_t *e) +static void +election_complete(election_t *e) { e->state = election_won; - - if(e->cb) { + if (e->cb != NULL) { e->cb(e); } - election_reset(e); } -static gboolean election_timer_cb(gpointer user_data) +static gboolean +election_timer_cb(gpointer user_data) { election_t *e = user_data; crm_info("%s timed out, declaring local node as winner", e->name); election_complete(e); return FALSE; } +/*! + * \brief Get current state of an election + * + * \param[in] e Election object + * + * \return Current state of \e + */ enum election_result election_state(election_t *e) { - if(e) { - return e->state; - } - return election_error; + return (e == NULL)? election_error : e->state; } /*! * \brief Create a new election object * * Every node that wishes to participate in an election must create an election * object. Typically, this should be done once, at start-up. A caller should * only create a single election object. * * \param[in] name Label for election (for logging) * \param[in] uname Local node's name * \param[in] period_ms How long to wait for all peers to vote * \param[in] cb Function to call if local node wins election * * \return Newly allocated election object on success, NULL on error * \note The caller is responsible for freeing the returned value using * election_fini(). */ election_t * election_init(const char *name, const char *uname, guint period_ms, GSourceFunc cb) { election_t *e = NULL; static guint count = 0; CRM_CHECK(uname != NULL, return NULL); e = calloc(1, sizeof(election_t)); if (e == NULL) { crm_perror(LOG_CRIT, "Cannot create election"); return NULL; } e->uname = strdup(uname); if (e->uname == NULL) { crm_perror(LOG_CRIT, "Cannot create election"); free(e); return NULL; } e->name = name? crm_strdup_printf("election-%s", name) : crm_strdup_printf("election-%u", count++); e->cb = cb; e->timeout = mainloop_timer_add(e->name, period_ms, FALSE, election_timer_cb, e); crm_trace("Created %s", e->name); return e; } /*! * \brief Disregard any previous vote by specified peer * * This discards any recorded vote from a specified peer. Election users should * call this whenever a voting peer becomes inactive. * * \param[in] e Election object * \param[in] uname Name of peer to disregard */ void election_remove(election_t *e, const char *uname) { - if(e && uname && e->voted) { + if ((e != NULL) && (uname != NULL) && (e->voted != NULL)) { crm_trace("Discarding %s (no-)vote from lost peer %s", e->name, uname); g_hash_table_remove(e->voted, uname); } } /*! * \brief Stop election timer and disregard all votes * * \param[in] e Election object */ void election_reset(election_t *e) { if (e != NULL) { crm_trace("Resetting election %s", e->name); mainloop_timer_stop(e->timeout); if (e->voted) { crm_trace("Destroying voted cache with %d members", g_hash_table_size(e->voted)); g_hash_table_destroy(e->voted); e->voted = NULL; } } } /*! * \brief Free an election object * * Free all memory associated with an election object, stopping its * election timer (if running). * * \param[in] e Election object */ void election_fini(election_t *e) { - if(e) { + if (e != NULL) { election_reset(e); crm_trace("Destroying %s", e->name); mainloop_timer_del(e->timeout); free(e->uname); free(e->name); free(e); } } static void election_timeout_start(election_t *e) { - if(e) { + if (e != NULL) { mainloop_timer_start(e->timeout); } } /*! * \brief Stop an election's timer, if running * * \param[in] e Election object */ void election_timeout_stop(election_t *e) { - if(e) { + if (e != NULL) { mainloop_timer_stop(e->timeout); } } /*! * \brief Change an election's timeout (restarting timer if running) * * \param[in] e Election object * \param[in] period New timeout */ void election_timeout_set_period(election_t *e, guint period) { - if(e) { + if (e != NULL) { mainloop_timer_set_period(e->timeout, period); } else { crm_err("No election defined"); } } static int -crm_uptime(struct timeval *output) +get_uptime(struct timeval *output) { static time_t expires = 0; static struct rusage info; time_t tm_now = time(NULL); if (expires < tm_now) { int rc = 0; info.ru_utime.tv_sec = 0; info.ru_utime.tv_usec = 0; rc = getrusage(RUSAGE_SELF, &info); output->tv_sec = 0; output->tv_usec = 0; if (rc < 0) { crm_perror(LOG_ERR, "Could not calculate the current uptime"); expires = 0; return -1; } crm_debug("Current CPU usage is: %lds, %ldus", (long)info.ru_utime.tv_sec, (long)info.ru_utime.tv_usec); } expires = tm_now + STORM_INTERVAL; /* N seconds after the last _access_ */ output->tv_sec = info.ru_utime.tv_sec; output->tv_usec = info.ru_utime.tv_usec; return 1; } static int -crm_compare_age(struct timeval your_age) +compare_age(struct timeval your_age) { struct timeval our_age; - crm_uptime(&our_age); /* If an error occurred, our_age will be compared as {0,0} */ + get_uptime(&our_age); /* If an error occurred, our_age will be compared as {0,0} */ if (our_age.tv_sec > your_age.tv_sec) { crm_debug("Win: %ld vs %ld (seconds)", (long)our_age.tv_sec, (long)your_age.tv_sec); return 1; } else if (our_age.tv_sec < your_age.tv_sec) { crm_debug("Lose: %ld vs %ld (seconds)", (long)our_age.tv_sec, (long)your_age.tv_sec); return -1; } else if (our_age.tv_usec > your_age.tv_usec) { crm_debug("Win: %ld.%06ld vs %ld.%06ld (usec)", (long)our_age.tv_sec, (long)our_age.tv_usec, (long)your_age.tv_sec, (long)your_age.tv_usec); return 1; } else if (our_age.tv_usec < your_age.tv_usec) { crm_debug("Lose: %ld.%06ld vs %ld.%06ld (usec)", (long)our_age.tv_sec, (long)our_age.tv_usec, (long)your_age.tv_sec, (long)your_age.tv_usec); return -1; } return 0; } /*! * \brief Start a new election by offering local node's candidacy * * Broadcast a "vote" election message containing the local node's ID, * (incremented) election counter, and uptime, and start the election timer. * * \param[in] e Election object * \note Any nodes agreeing to the candidacy will send a "no-vote" reply, and if * all active peers do so, or if the election times out, the local node * wins the election. (If we lose to any peer vote, we will stop the * timer, so a timeout means we did not lose -- either some peer did not * vote, or we did not call election_check() in time.) */ void election_vote(election_t *e) { struct timeval age; xmlNode *vote = NULL; crm_node_t *our_node; if (e == NULL) { crm_trace("Election vote requested, but no election available"); return; } our_node = crm_get_peer(0, e->uname); if ((our_node == NULL) || (crm_is_peer_active(our_node) == FALSE)) { crm_trace("Cannot vote in %s yet: local node not connected to cluster", e->name); return; } election_reset(e); e->state = election_in_progress; vote = create_request(CRM_OP_VOTE, NULL, NULL, CRM_SYSTEM_CRMD, CRM_SYSTEM_CRMD, NULL); e->count++; crm_xml_add(vote, F_CRM_ELECTION_OWNER, our_node->uuid); crm_xml_add_int(vote, F_CRM_ELECTION_ID, e->count); - crm_uptime(&age); + get_uptime(&age); crm_xml_add_timeval(vote, F_CRM_ELECTION_AGE_S, F_CRM_ELECTION_AGE_US, &age); send_cluster_message(NULL, crm_msg_crmd, vote, TRUE); free_xml(vote); crm_debug("Started %s round %d", e->name, e->count); election_timeout_start(e); return; } /*! * \brief Check whether local node has won an election * * If all known peers have sent no-vote messages, stop the election timer, set * the election state to won, and call any registered win callback. * * \param[in] e Election object * * \return TRUE if local node has won, FALSE otherwise * \note If all known peers have sent no-vote messages, but the election owner * does not call this function, the election will not be won (and the * callback will not be called) until the election times out. * \note This should be called when election_count_vote() returns * \c election_in_progress. */ bool election_check(election_t *e) { int voted_size = 0; int num_members = 0; - if(e == NULL) { + if (e == NULL) { crm_trace("Election check requested, but no election available"); return FALSE; } if (e->voted == NULL) { crm_trace("%s check requested, but no votes received yet", e->name); return FALSE; } voted_size = g_hash_table_size(e->voted); num_members = crm_active_peers(); /* in the case of #voted > #members, it is better to * wait for the timeout and give the cluster time to * stabilize */ if (voted_size >= num_members) { /* we won and everyone has voted */ election_timeout_stop(e); if (voted_size > num_members) { GHashTableIter gIter; const crm_node_t *node; char *key = NULL; crm_warn("Received too many votes in %s", e->name); g_hash_table_iter_init(&gIter, crm_peer_cache); while (g_hash_table_iter_next(&gIter, NULL, (gpointer *) & node)) { if (crm_is_peer_active(node)) { crm_warn("* expected vote: %s", node->uname); } } g_hash_table_iter_init(&gIter, e->voted); while (g_hash_table_iter_next(&gIter, (gpointer *) & key, NULL)) { crm_warn("* actual vote: %s", key); } } crm_info("%s won by local node", e->name); election_complete(e); return TRUE; } else { crm_debug("%s still waiting on %d of %d votes", e->name, num_members - voted_size, num_members); } return FALSE; } #define LOSS_DAMPEN 2 /* in seconds */ struct vote { const char *op; const char *from; const char *version; const char *election_owner; int election_id; struct timeval age; }; /*! * \brief Unpack an election message * * \param[in] e Election object * \param[in] message Election message XML * \param[out] vote Parsed fields from message * * \return TRUE if election message and election are valid, FALSE otherwise * \note The parsed struct's pointer members are valid only for the lifetime of * the message argument. */ static bool parse_election_message(election_t *e, xmlNode *message, struct vote *vote) { CRM_CHECK(message && vote, return FALSE); vote->election_id = -1; vote->age.tv_sec = -1; vote->age.tv_usec = -1; vote->op = crm_element_value(message, F_CRM_TASK); vote->from = crm_element_value(message, F_CRM_HOST_FROM); vote->version = crm_element_value(message, F_CRM_VERSION); vote->election_owner = crm_element_value(message, F_CRM_ELECTION_OWNER); crm_element_value_int(message, F_CRM_ELECTION_ID, &(vote->election_id)); if ((vote->op == NULL) || (vote->from == NULL) || (vote->version == NULL) || (vote->election_owner == NULL) || (vote->election_id < 0)) { crm_warn("Invalid %s message from %s in %s ", (vote->op? vote->op : "election"), (vote->from? vote->from : "unspecified node"), (e? e->name : "election")); return FALSE; } // Op-specific validation if (pcmk__str_eq(vote->op, CRM_OP_VOTE, pcmk__str_none)) { // Only vote ops have uptime crm_element_value_timeval(message, F_CRM_ELECTION_AGE_S, F_CRM_ELECTION_AGE_US, &(vote->age)); if ((vote->age.tv_sec < 0) || (vote->age.tv_usec < 0)) { crm_warn("Cannot count %s %s from %s because it is missing uptime", (e? e->name : "election"), vote->op, vote->from); return FALSE; } } else if (!pcmk__str_eq(vote->op, CRM_OP_NOVOTE, pcmk__str_none)) { crm_info("Cannot process %s message from %s because %s is not a known election op", (e? e->name : "election"), vote->from, vote->op); return FALSE; } // Election validation if (e == NULL) { crm_info("Cannot count %s from %s because no election available", vote->op, vote->from); return FALSE; } /* If the membership cache is NULL, we REALLY shouldn't be voting -- * the question is how we managed to get here. */ if (crm_peer_cache == NULL) { crm_info("Cannot count %s %s from %s because no peer information available", e->name, vote->op, vote->from); return FALSE; } return TRUE; } static void record_vote(election_t *e, struct vote *vote) { char *voter_copy = NULL; char *vote_copy = NULL; CRM_ASSERT(e && vote && vote->from && vote->op); if (e->voted == NULL) { e->voted = crm_str_table_new(); } voter_copy = strdup(vote->from); vote_copy = strdup(vote->op); CRM_ASSERT(voter_copy && vote_copy); g_hash_table_replace(e->voted, voter_copy, vote_copy); } static void send_no_vote(crm_node_t *peer, struct vote *vote) { // @TODO probably shouldn't hardcode CRM_SYSTEM_CRMD and crm_msg_crmd xmlNode *novote = create_request(CRM_OP_NOVOTE, NULL, vote->from, CRM_SYSTEM_CRMD, CRM_SYSTEM_CRMD, NULL); crm_xml_add(novote, F_CRM_ELECTION_OWNER, vote->election_owner); crm_xml_add_int(novote, F_CRM_ELECTION_ID, vote->election_id); send_cluster_message(peer, crm_msg_crmd, novote, TRUE); free_xml(novote); } /*! * \brief Process an election message (vote or no-vote) from a peer * * \param[in] e Election object * \param[in] vote Election message XML from peer * \param[in] can_win Whether to consider the local node eligible for winning * * \return Election state after new vote is considered * \note If the peer message is a vote, and we prefer the peer to win, this will * send a no-vote reply to the peer. * \note The situations "we lost to this vote" from "this is a late no-vote * after we've already lost" both return election_lost. If a caller needs * to distinguish them, it should save the current state before calling * this function, and then compare the result. */ enum election_result election_count_vote(election_t *e, xmlNode *message, bool can_win) { int log_level = LOG_INFO; gboolean done = FALSE; gboolean we_lose = FALSE; const char *reason = "unknown"; bool we_are_owner = FALSE; crm_node_t *our_node = NULL, *your_node = NULL; time_t tm_now = time(NULL); struct vote vote; CRM_CHECK(message != NULL, return election_error); if (parse_election_message(e, message, &vote) == FALSE) { return election_error; } your_node = crm_get_peer(0, vote.from); our_node = crm_get_peer(0, e->uname); we_are_owner = (our_node != NULL) && pcmk__str_eq(our_node->uuid, vote.election_owner, pcmk__str_none); - if(can_win == FALSE) { + if (!can_win) { reason = "Not eligible"; we_lose = TRUE; } else if (our_node == NULL || crm_is_peer_active(our_node) == FALSE) { reason = "We are not part of the cluster"; log_level = LOG_ERR; we_lose = TRUE; } else if (we_are_owner && (vote.election_id != e->count)) { log_level = LOG_TRACE; reason = "Superseded"; done = TRUE; } else if (your_node == NULL || crm_is_peer_active(your_node) == FALSE) { /* Possibly we cached the message in the FSA queue at a point that it wasn't */ reason = "Peer is not part of our cluster"; log_level = LOG_WARNING; done = TRUE; } else if (pcmk__str_eq(vote.op, CRM_OP_NOVOTE, pcmk__str_none) || pcmk__str_eq(vote.from, e->uname, pcmk__str_none)) { /* Receiving our own broadcast vote, or a no-vote from peer, is a vote * for us to win */ if (!we_are_owner) { crm_warn("Cannot count %s round %d %s from %s because we are not election owner (%s)", e->name, vote.election_id, vote.op, vote.from, vote.election_owner); return election_error; } if (e->state != election_in_progress) { // Should only happen if we already lost crm_debug("Not counting %s round %d %s from %s because no election in progress", e->name, vote.election_id, vote.op, vote.from); return e->state; } record_vote(e, &vote); reason = "Recorded"; done = TRUE; } else { // A peer vote requires a comparison to determine which node is better - int age_result = crm_compare_age(vote.age); + int age_result = compare_age(vote.age); int version_result = compare_version(vote.version, CRM_FEATURE_SET); if (version_result < 0) { reason = "Version"; we_lose = TRUE; } else if (version_result > 0) { reason = "Version"; } else if (age_result < 0) { reason = "Uptime"; we_lose = TRUE; } else if (age_result > 0) { reason = "Uptime"; } else if (strcasecmp(e->uname, vote.from) > 0) { reason = "Host name"; we_lose = TRUE; } else { reason = "Host name"; } } if (e->expires < tm_now) { e->election_wins = 0; e->expires = tm_now + STORM_INTERVAL; } else if (done == FALSE && we_lose == FALSE) { int peers = 1 + g_hash_table_size(crm_peer_cache); /* If every node has to vote down every other node, thats N*(N-1) total elections * Allow some leeway before _really_ complaining */ e->election_wins++; if (e->election_wins > (peers * peers)) { crm_warn("%s election storm detected: %d wins in %d seconds", e->name, e->election_wins, STORM_INTERVAL); e->election_wins = 0; e->expires = tm_now + STORM_INTERVAL; if (e->wrote_blackbox == FALSE) { /* It's questionable whether a black box (from every node in the * cluster) would be truly helpful in diagnosing an election * storm. It's also highly doubtful a production environment * would get multiple election storms from distinct causes, so * saving one blackbox per process lifetime should be * sufficient. Alternatives would be to save a timestamp of the * last blackbox write instead of a boolean, and write a new one * if some amount of time has passed; or to save a storm count, * write a blackbox on every Nth occurrence. */ crm_write_blackbox(0, NULL); e->wrote_blackbox = TRUE; } } } if (done) { do_crm_log(log_level + 1, "Processed %s round %d %s (current round %d) from %s (%s)", e->name, vote.election_id, vote.op, e->count, vote.from, reason); return e->state; } else if (we_lose == FALSE) { /* We track the time of the last election loss to implement an election * dampening period, reducing the likelihood of an election storm. If * this node has lost within the dampening period, don't start a new * election, even if we win against a peer's vote -- the peer we lost to * should win again. * * @TODO This has a problem case: if an election winner immediately * leaves the cluster, and a new election is immediately called, all * nodes could lose, with no new winner elected. The ideal solution * would be to tie the election structure with the peer caches, which * would allow us to clear the dampening when the previous winner * leaves (and would allow other improvements as well). */ if ((e->last_election_loss == 0) || ((tm_now - e->last_election_loss) > (time_t) LOSS_DAMPEN)) { do_crm_log(log_level, "%s round %d (owner node ID %s) pass: %s from %s (%s)", e->name, vote.election_id, vote.election_owner, vote.op, vote.from, reason); e->last_election_loss = 0; election_timeout_stop(e); /* Start a new election by voting down this, and other, peers */ e->state = election_start; return e->state; } else { char *loss_time = ctime(&e->last_election_loss); if (loss_time) { // Show only HH:MM:SS loss_time += 11; loss_time[8] = '\0'; } crm_info("Ignoring %s round %d (owner node ID %s) pass vs %s because we lost less than %ds ago at %s", e->name, vote.election_id, vote.election_owner, vote.from, LOSS_DAMPEN, (loss_time? loss_time : "unknown")); } } e->last_election_loss = tm_now; do_crm_log(log_level, "%s round %d (owner node ID %s) lost: %s from %s (%s)", e->name, vote.election_id, vote.election_owner, vote.op, vote.from, reason); election_reset(e); send_no_vote(your_node, &vote); e->state = election_lost; return e->state; } /*! * \brief Reset any election dampening currently in effect * * \param[in] e Election object to clear */ void election_clear_dampening(election_t *e) { e->last_election_loss = 0; }