Add command line option --snapshot-to-json 📦

libraries/chain/include/eosio/chain/snapshot.hpp

@@ -342,7 +342,22 @@ namespace eosio { namespace chain {
          std::streampos          header_pos;
          std::streampos          section_pos;
          uint64_t                row_count;
+   };
+
+   class ostream_json_snapshot_writer : public snapshot_writer {
+      public:
+         explicit ostream_json_snapshot_writer(std::ostream& snapshot);
+
+         void write_start_section( const std::string& section_name ) override;
+         void write_row( const detail::abstract_snapshot_row_writer& row_writer ) override;
+         void write_end_section() override;
+         void finalize();
+
+         static const uint32_t magic_number = 0x30510550;
 
+      private:
+         detail::ostream_wrapper snapshot;
+         uint64_t                row_count;
    };
 
    class istream_snapshot_reader : public snapshot_reader {

libraries/chain/snapshot.cpp

@@ -1,6 +1,7 @@
 #include <eosio/chain/snapshot.hpp>
 #include <eosio/chain/exceptions.hpp>
 #include <fc/scoped_exit.hpp>
+#include <fc/io/json.hpp>
 
 namespace eosio { namespace chain {
 
@@ -190,6 +191,44 @@ void ostream_snapshot_writer::finalize() {
    snapshot.write((char*)&end_marker, sizeof(end_marker));
 }
 
+ostream_json_snapshot_writer::ostream_json_snapshot_writer(std::ostream& snapshot)
+      :snapshot(snapshot)
+      ,row_count(0)
+{
+   snapshot << "{\n";
+   // write magic number
+   auto totem = magic_number;
+   snapshot << "\"magic_number\":" << fc::json::to_string(totem, fc::time_point::maximum()) << "\n";
+
+   // write version
+   auto version = current_snapshot_version;
+   snapshot << ",\"version\":" << fc::json::to_string(version, fc::time_point::maximum()) << "\n";
+}
+
+void ostream_json_snapshot_writer::write_start_section( const std::string& section_name )
+{
+   snapshot.inner << "," << fc::json::to_string(section_name, fc::time_point::maximum()) << ":{\n";
+}
+
+void ostream_json_snapshot_writer::write_row( const detail::abstract_snapshot_row_writer& row_writer ) {
+   const auto yield = [&](size_t s) {};
+
+   if(row_count != 0) snapshot.inner << ",";
+   snapshot.inner << "\"row_" << row_count << "\":" << fc::json::to_string(row_writer.to_variant(), yield) << "\n";
+   ++row_count;
+}
+
+void ostream_json_snapshot_writer::write_end_section( ) {
+   snapshot.inner << "}\n";
+   row_count = 0;
+}
+
+void ostream_json_snapshot_writer::finalize() {
+   snapshot.inner << "}\n";
+   snapshot.inner.flush();
+}
+
+
 istream_snapshot_reader::istream_snapshot_reader(std::istream& snapshot)
 :snapshot(snapshot)
 ,header_pos(snapshot.tellg())

plugins/chain_plugin/chain_plugin.cpp

@@ -427,6 +427,8 @@ void chain_plugin::set_program_options(options_description& cli, options_descrip
           "print build environment information to console as JSON and exit")
          ("extract-build-info", bpo::value<bfs::path>(),
           "extract build environment information as JSON, write into specified file, and exit")
+         ("snapshot-to-json", bpo::value<bfs::path>(),
+          "convert snapshot to JSON format, and exit")
          ("force-all-checks", bpo::bool_switch()->default_value(false),
           "do not skip any validation checks while replaying blocks (useful for replaying blocks from untrusted source)")
          ("disable-replay-opts", bpo::bool_switch()->default_value(false),
@@ -963,6 +965,57 @@ void chain_plugin::plugin_initialize(const variables_map& options) {
          EOS_THROW( extract_genesis_state_exception, "extracted genesis state from blocks.log" );
       }
 
+      std::optional<chain_id_type> chain_id;
+      if( options.count("snapshot-to-json") ) {
+         my->snapshot_path = options.at( "snapshot-to-json" ).as<bfs::path>();
+         EOS_ASSERT( fc::exists(*my->snapshot_path), plugin_config_exception,
+                     "Cannot load snapshot, ${name} does not exist", ("name", my->snapshot_path->generic_string()) );
+
+         // recover genesis information from the snapshot
+         // used for validation code below
+         auto infile = std::ifstream(my->snapshot_path->generic_string(), (std::ios::in | std::ios::binary));
+         istream_snapshot_reader reader(infile);
+         reader.validate();
+         chain_id = controller::extract_chain_id(reader);
+         infile.close();
+
+         boost::filesystem::path temp_dir = boost::filesystem::temp_directory_path() / boost::filesystem::unique_path();
+         my->chain_config->state_dir = temp_dir / "state";
+         my->blocks_dir = temp_dir / "blocks";
+         my->chain_config->blog.log_dir = my->blocks_dir;
+         try {
+            auto shutdown = [](){ return app().quit(); };
+            auto check_shutdown = [](){ return app().is_quiting(); };
+            auto infile = std::ifstream(my->snapshot_path->generic_string(), (std::ios::in | std::ios::binary));
+            auto reader = std::make_shared<istream_snapshot_reader>(infile);
+            my->chain.emplace( *my->chain_config, std::move(pfs), *chain_id );
+            my->chain->add_indices();
+            my->chain->startup(shutdown, check_shutdown, reader);
+            infile.close();
+            app().quit(); // shutdown as we will be finished after writing the snapshot
+
+            ilog("Writing snapshot: ${s}", ("s", my->snapshot_path->generic_string() + ".json"));
+            auto snap_out = std::ofstream( my->snapshot_path->generic_string() + ".json", (std::ios::out) );
+            auto writer = std::make_shared<ostream_json_snapshot_writer>( snap_out );
+            my->chain->write_snapshot( writer );
+            writer->finalize();
+            snap_out.flush();
+            snap_out.close();
+         } catch (const database_guard_exception& e) {
+            log_guard_exception(e);
+            // make sure to properly close the db
+            my->chain.reset();
+            fc::remove_all(temp_dir);
+            throw;
+         }
+         my->chain.reset();
+         fc::remove_all(temp_dir);
+         ilog("Completed writing snapshot: ${s}", ("s", my->snapshot_path->generic_string() + ".json"));
+         ilog("==== Ignore any additional log messages. ====");
+
+         EOS_THROW( node_management_success, "extracted json from snapshot" );
+      }
+
       // move fork_db to new location
       upgrade_from_reversible_to_fork_db( my.get() );
 
@@ -983,7 +1036,6 @@ void chain_plugin::plugin_initialize(const variables_map& options) {
          wlog( "The --truncate-at-block option can only be used with --hard-replay-blockchain." );
       }
 
-      std::optional<chain_id_type> chain_id;
       if (options.count( "snapshot" )) {
          my->snapshot_path = options.at( "snapshot" ).as<bfs::path>();
          EOS_ASSERT( fc::exists(*my->snapshot_path), plugin_config_exception,