Implement journal method to scan through contents, optionally matching a search pattern

src/Commands.cc

@@ -132,6 +132,8 @@ struct cmdMapInit {
     redis_cmd_map["raft_promote_observer"] = {RedisCommand::RAFT_PROMOTE_OBSERVER, CommandType::RAFT};
     redis_cmd_map["raft_heartbeat"] = {RedisCommand::RAFT_HEARTBEAT, CommandType::RAFT};
     redis_cmd_map["raft_fetch_last"] = {RedisCommand::RAFT_FETCH_LAST, CommandType::RAFT};
+    redis_cmd_map["raft_journal_scan"] = {RedisCommand::RAFT_JOURNAL_SCAN, CommandType::RAFT};
+
     redis_cmd_map["activate_stale_reads"] = {RedisCommand::ACTIVATE_STALE_READS, CommandType::RAFT};
 
     redis_cmd_map["quarkdb_info"] = {RedisCommand::QUARKDB_INFO, CommandType::QUARKDB};

src/Commands.hh

@@ -139,6 +139,8 @@ enum class RedisCommand {
   RAFT_PROMOTE_OBSERVER,
   RAFT_HEARTBEAT,
   RAFT_FETCH_LAST,
+  RAFT_JOURNAL_SCAN,
+
   ACTIVATE_STALE_READS,
 
   QUARKDB_INFO,

src/raft/RaftJournal.cc

@@ -30,6 +30,7 @@
 #include "../utils/IntToBinaryString.hh"
 #include "../utils/StaticBuffer.hh"
 #include "../utils/StringUtils.hh"
+#include "../../deps/StringMatchLen.h"
 #include "RaftState.hh"
 #include <rocksdb/utilities/checkpoint.h>
 #include <rocksdb/filter_policy.h>
@@ -540,6 +541,40 @@ rocksdb::Status RaftJournal::checkpoint(const std::string &path) {
   return st;
 }
 
+//------------------------------------------------------------------------------
+// Scan through the contents of the journal, starting from the given index
+//------------------------------------------------------------------------------
+rocksdb::Status RaftJournal::scanContents(LogIndex startingPoint, size_t count, std::string_view match, std::vector<RaftEntry> &out, LogIndex &nextCursor) {
+  out.clear();
+  RaftJournal::Iterator iter = getIterator(startingPoint);
+
+  for(size_t i = 0; i < count; i++) {
+    if(!iter.valid()) {
+      break;
+    }
+
+    RaftSerializedEntry item;
+    iter.current(item);
+
+    if(match.empty() || stringmatchlen(match.data(), match.length(), item.data(), item.length(), 0) == 1) {
+      RaftEntry entry;
+      RaftEntry::deserialize(entry, item);
+      out.emplace_back(entry);
+    }
+
+    iter.next();
+  }
+
+  if(!iter.valid()) {
+    nextCursor = 0;
+  }
+  else {
+    nextCursor = iter.getCurrentIndex();
+  }
+
+  return rocksdb::Status::OK();
+}
+
 //------------------------------------------------------------------------------
 // Iterator
 //------------------------------------------------------------------------------
@@ -597,3 +632,7 @@ void RaftJournal::Iterator::current(RaftSerializedEntry &entry) {
   qdb_assert(this->valid());
   entry = iter->value().ToString();
 }
+
+LogIndex RaftJournal::Iterator::getCurrentIndex() const {
+  return currentIndex;
+}

src/raft/RaftJournal.hh

@@ -96,6 +96,7 @@ public:
     bool valid();
     void next();
     void current(RaftSerializedEntry &entry);
+    LogIndex getCurrentIndex() const;
   private:
     void validate();
     LogIndex currentIndex;
@@ -103,6 +104,7 @@ public:
   };
 
   Iterator getIterator(LogIndex startingPoint);
+  rocksdb::Status scanContents(LogIndex startingPoint, size_t count, std::string_view match, std::vector<RaftEntry> &out, LogIndex &nextCursor);
 
 private:
   void openDB(const std::string &path);

test/e2e.cc

@@ -2153,6 +2153,36 @@ TEST_F(Raft_e2e, vhset) {
     "2) 1) \"f9\"\n"
     "   2) \"v9\"\n"
   );
+}
+
+TEST_F(Raft_e2e, JournalScanning) {
+  for(size_t i = 1; i <= 5; i ++) {
+    RaftEntry entry(0, {"set", SSTR("k" << i), SSTR("v" << i) } );
+    ASSERT_TRUE(journal(0)->append(i, entry));
+    ASSERT_TRUE(journal(1)->append(i, entry));
+    ASSERT_TRUE(journal(2)->append(i, entry));
+  }
+
+  std::vector<RaftEntry> entries;
+  LogIndex cursor;
+  ASSERT_OK(journal(0)->scanContents(1, 3, "", entries, cursor));
+  ASSERT_EQ(entries.size(), 3u);
+  ASSERT_EQ(cursor, 4);
+
+  for(size_t i = 1; i <= 3; i ++) {
+    RaftEntry entry(0, {"set", SSTR("k" << i), SSTR("v" << i) } );
+    ASSERT_EQ(entries[i-1], entry);
+  }
+
+  ASSERT_OK(journal(0)->scanContents(0, 300, "*k2*", entries, cursor));
+  ASSERT_EQ(entries.size(), 1u);
+  ASSERT_EQ(cursor, 0);
+
+  RaftEntry entry(0, {"set", "k2", "v2"});
+  ASSERT_EQ(entries[0], entry);
+
+
+
 
 
 }