From 0f954f326dcd83ef8c70aebf19194adc0b1b69b9 Mon Sep 17 00:00:00 2001 From: Han Zhou Date: Fri, 12 Apr 2019 16:26:22 -0700 Subject: ovsdb raft: Sync commit index to followers without delay. When update is requested from follower, the leader sends AppendRequest to all followers and wait until AppendReply received from majority, and then it will update commit index - the new entry is regarded as committed in raft log. However, this commit will not be notified to followers (including the one initiated the request) until next heartbeat (ping timeout), if no other pending requests. This results in long latency for updates made through followers, especially when a batch of updates are requested through the same follower. $ time for i in `seq 1 100`; do ovn-nbctl ls-add ls$i; done real 0m34.154s user 0m0.083s sys 0m0.250s This patch solves the problem by sending heartbeat as soon as the commit index is updated in leader. It also avoids unnessary heartbeat by resetting the ping timer whenever AppendRequest is broadcasted. With this patch the performance is improved more than 50 times in same test: $ time for i in `seq 1 100`; do ovn-nbctl ls-add ls$i; done real 0m0.564s user 0m0.080s sys 0m0.199s Torture test cases are also updated because otherwise the tests will all be skipped because of the improved performance. Signed-off-by: Han Zhou Signed-off-by: Ben Pfaff --- ovsdb/raft.c | 43 +++++++++++++++++++++++++++++-------------- 1 file changed, 29 insertions(+), 14 deletions(-) (limited to 'ovsdb/raft.c') diff --git a/ovsdb/raft.c b/ovsdb/raft.c index eee4f336a..31e9e7245 100644 --- a/ovsdb/raft.c +++ b/ovsdb/raft.c @@ -320,7 +320,8 @@ static void raft_send_append_request(struct raft *, static void raft_become_leader(struct raft *); static void raft_become_follower(struct raft *); -static void raft_reset_timer(struct raft *); +static void raft_reset_election_timer(struct raft *); +static void raft_reset_ping_timer(struct raft *); static void raft_send_heartbeats(struct raft *); static void raft_start_election(struct raft *, bool leadership_transfer); static bool raft_truncate(struct raft *, uint64_t new_end); @@ -376,8 +377,8 @@ raft_alloc(void) hmap_init(&raft->add_servers); hmap_init(&raft->commands); - raft->ping_timeout = time_msec() + PING_TIME_MSEC; - raft_reset_timer(raft); + raft_reset_ping_timer(raft); + raft_reset_election_timer(raft); return raft; } @@ -865,7 +866,7 @@ raft_read_log(struct raft *raft) } static void -raft_reset_timer(struct raft *raft) +raft_reset_election_timer(struct raft *raft) { unsigned int duration = (ELECTION_BASE_MSEC + random_range(ELECTION_RANGE_MSEC)); @@ -873,6 +874,12 @@ raft_reset_timer(struct raft *raft) raft->election_timeout = raft->election_base + duration; } +static void +raft_reset_ping_timer(struct raft *raft) +{ + raft->ping_timeout = time_msec() + PING_TIME_MSEC; +} + static void raft_add_conn(struct raft *raft, struct jsonrpc_session *js, const struct uuid *sid, bool incoming) @@ -1603,7 +1610,7 @@ raft_start_election(struct raft *raft, bool leadership_transfer) VLOG_INFO("term %"PRIu64": starting election", raft->term); } } - raft_reset_timer(raft); + raft_reset_election_timer(raft); struct raft_server *peer; HMAP_FOR_EACH (peer, hmap_node, &raft->servers) { @@ -1782,8 +1789,8 @@ raft_run(struct raft *raft) raft_command_complete(raft, cmd, RAFT_CMD_TIMEOUT); } } + raft_reset_ping_timer(raft); } - raft->ping_timeout = time_msec() + PING_TIME_MSEC; } /* Do this only at the end; if we did it as soon as we set raft->left or @@ -1963,6 +1970,7 @@ raft_command_initiate(struct raft *raft, s->next_index++; } } + raft_reset_ping_timer(raft); return cmd; } @@ -2313,7 +2321,7 @@ raft_become_follower(struct raft *raft) } raft->role = RAFT_FOLLOWER; - raft_reset_timer(raft); + raft_reset_election_timer(raft); /* Notify clients about lost leadership. * @@ -2387,6 +2395,8 @@ raft_send_heartbeats(struct raft *raft) RAFT_CMD_INCOMPLETE, 0); } } + + raft_reset_ping_timer(raft); } /* Initializes the fields in 's' that represent the leader's view of the @@ -2413,7 +2423,7 @@ raft_become_leader(struct raft *raft) raft->role = RAFT_LEADER; raft->leader_sid = raft->sid; raft->election_timeout = LLONG_MAX; - raft->ping_timeout = time_msec() + PING_TIME_MSEC; + raft_reset_ping_timer(raft); struct raft_server *s; HMAP_FOR_EACH (s, hmap_node, &raft->servers) { @@ -2573,11 +2583,13 @@ raft_get_next_entry(struct raft *raft, struct uuid *eid) return data; } -static void +/* Updates commit index in raft log. If commit index is already up-to-date + * it does nothing and return false, otherwise, returns true. */ +static bool raft_update_commit_index(struct raft *raft, uint64_t new_commit_index) { if (new_commit_index <= raft->commit_index) { - return; + return false; } if (raft->role == RAFT_LEADER) { @@ -2610,6 +2622,7 @@ raft_update_commit_index(struct raft *raft, uint64_t new_commit_index) .commit_index = raft->commit_index, }; ignore(ovsdb_log_write_and_free(raft->log, raft_record_to_json(&r))); + return true; } /* This doesn't use rq->entries (but it does use rq->n_entries). */ @@ -2809,7 +2822,7 @@ raft_handle_append_request(struct raft *raft, "usurped leadership"); return; } - raft_reset_timer(raft); + raft_reset_election_timer(raft); /* First check for the common case, where the AppendEntries request is * entirely for indexes covered by 'log_start' ... 'log_end - 1', something @@ -3045,7 +3058,9 @@ raft_consider_updating_commit_index(struct raft *raft) } } } - raft_update_commit_index(raft, new_commit_index); + if (raft_update_commit_index(raft, new_commit_index)) { + raft_send_heartbeats(raft); + } } static void @@ -3274,7 +3289,7 @@ raft_handle_vote_request__(struct raft *raft, return false; } - raft_reset_timer(raft); + raft_reset_election_timer(raft); return true; } @@ -3697,7 +3712,7 @@ static bool raft_handle_install_snapshot_request__( struct raft *raft, const struct raft_install_snapshot_request *rq) { - raft_reset_timer(raft); + raft_reset_election_timer(raft); /* * Our behavior here depend on new_log_start in the snapshot compared to -- cgit v1.2.1