From 10fd97c32dc6c66b7b311216b9e130d958f01602 Mon Sep 17 00:00:00 2001
From: kishorenc <kishorenc@gmail.com>
Date: Thu, 24 Dec 2020 19:32:17 +0530
Subject: [PATCH] Node vote API for triggering leader rotation.

---
 include/core_api.h            |  6 +++++-
 include/http_server.h         |  2 ++
 include/raft_server.h         |  6 +++++-
 src/core_api.cpp              | 11 +++++++++++
 src/http_server.cpp           |  4 ++++
 src/main/typesense_server.cpp |  1 +
 src/raft_server.cpp           | 11 +++++++++++
 7 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/include/core_api.h b/include/core_api.h
index ee0bbb25..9c35f2a1 100644
--- a/include/core_api.h
+++ b/include/core_api.h
@@ -73,7 +73,7 @@ bool get_key(http_req& req, http_res& res);
 
 bool del_key(http_req& req, http_res& res);
 
-// Metrics
+// Health + Metrics
 
 bool get_debug(http_req& req, http_res& res);
 
@@ -85,8 +85,12 @@ bool get_metrics_json(http_req& req, http_res& res);
 
 bool get_log_sequence(http_req& req, http_res& res);
 
+// operations
+
 bool post_snapshot(http_req& req, http_res& res);
 
+bool post_vote(http_req& req, http_res& res);
+
 // Misc helpers
 
 bool raft_write_send_response(void *data);
diff --git a/include/http_server.h b/include/http_server.h
index 51f8bade..3a0acb5b 100644
--- a/include/http_server.h
+++ b/include/http_server.h
@@ -173,4 +173,6 @@ public:
     void defer_processing(http_req& req, http_res& res, size_t timeout_ms);
 
     void do_snapshot(const std::string& snapshot_path, http_req& req, http_res& res);
+
+    bool trigger_vote();
 };
diff --git a/include/raft_server.h b/include/raft_server.h
index b5e11693..248d528a 100644
--- a/include/raft_server.h
+++ b/include/raft_server.h
@@ -94,7 +94,7 @@ public:
 class ReplicationState : public braft::StateMachine {
 private:
     static constexpr const char* db_snapshot_name = "db_snapshot";
-    static const size_t CATCHUP_MIN_SEQUENCE_DIFF = 3000;  // ~ actual 1K documents
+    static const size_t CATCHUP_MIN_SEQUENCE_DIFF = 3000;
 
     braft::Node* volatile node;
     butil::atomic<int64_t> leader_term;
@@ -117,6 +117,8 @@ private:
 
     std::string ext_snapshot_path;
 
+    int election_timeout_interval_ms;
+
 public:
 
     static constexpr const char* log_dir_name = "log";
@@ -141,6 +143,8 @@ public:
     // updates cluster membership
     void refresh_nodes(const std::string & nodes);
 
+    bool trigger_vote();
+
     bool has_leader_term() const {
         return leader_term.load(butil::memory_order_acquire) > 0;
     }
diff --git a/src/core_api.cpp b/src/core_api.cpp
index a415096e..f8e4d8f9 100644
--- a/src/core_api.cpp
+++ b/src/core_api.cpp
@@ -1340,6 +1340,17 @@ bool post_snapshot(http_req& req, http_res& res) {
     return true;
 }
 
+bool post_vote(http_req& req, http_res& res) {
+    res.status_code = 200;
+    res.content_type_header = "application/json";
+
+    nlohmann::json response;
+    response["success"] = server->trigger_vote();
+    res.body = response.dump();
+
+    return true;
+}
+
 bool get_synonyms(http_req &req, http_res &res) {
     CollectionManager & collectionManager = CollectionManager::get_instance();
     Collection *collection = collectionManager.get_collection(req.params["collection"]);
diff --git a/src/http_server.cpp b/src/http_server.cpp
index 25741a39..f808587e 100644
--- a/src/http_server.cpp
+++ b/src/http_server.cpp
@@ -809,3 +809,7 @@ bool HttpServer::has_exited() const {
 void HttpServer::do_snapshot(const std::string& snapshot_path, http_req& req, http_res& res) {
     return replication_state->do_snapshot(snapshot_path, req, res);
 }
+
+bool HttpServer::trigger_vote() {
+    return replication_state->trigger_vote();
+}
diff --git a/src/main/typesense_server.cpp b/src/main/typesense_server.cpp
index 38b396c1..a31b4fde 100644
--- a/src/main/typesense_server.cpp
+++ b/src/main/typesense_server.cpp
@@ -62,6 +62,7 @@ void master_server_routes() {
     server->post("/health", post_health);
     server->get("/sequence", get_log_sequence);
     server->post("/operations/snapshot", post_snapshot, false, true);
+    server->post("/operations/vote", post_vote, false, false);
 }
 
 int main(int argc, char **argv) {
diff --git a/src/raft_server.cpp b/src/raft_server.cpp
index 25fad5e0..2ff060b6 100644
--- a/src/raft_server.cpp
+++ b/src/raft_server.cpp
@@ -25,6 +25,7 @@ int ReplicationState::start(const butil::EndPoint & peering_endpoint, const int
                             int election_timeout_ms, int snapshot_interval_s,
                             const std::string & raft_dir, const std::string & nodes) {
 
+    this->election_timeout_interval_ms = election_timeout_ms;
     this->raft_dir_path = raft_dir;
 
     braft::NodeOptions node_options;
@@ -576,6 +577,16 @@ void ReplicationState::do_dummy_write() {
     LOG(INFO) << "Dummy write to " << url << ", status = " << status_code << ", response = " << api_res;
 }
 
+bool ReplicationState::trigger_vote() {
+    if(node) {
+        auto status = node->vote(election_timeout_interval_ms);
+        LOG(INFO) << "Triggered vote. Ok? " << status.ok() << ", status: " << status;
+        return status.ok();
+    }
+
+    return false;
+}
+
 void InitSnapshotClosure::Run() {
     // Auto delete this after Run()
     std::unique_ptr<InitSnapshotClosure> self_guard(this);