Add C binding for secondary instance (#5505)

Summary:
Add C binding for secondary instance as well as unit test.

Test plan (on devserver)
```
$make clean && COMPILE_WITH_ASAN=1 make -j20 all
$./c_test
$make check
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5505

Differential Revision: D16000043

Pulled By: riversand963

fbshipit-source-id: 3361ef6bfdf4ce12438cee7290a0ac203b5250bd

HISTORY.md

@@ -9,6 +9,8 @@
 * options.keep_log_file_num will be enforced strictly all the time. File names of all log files will be tracked, which may take significantly amount of memory if options.keep_log_file_num is large and either of options.max_log_file_size or options.log_file_time_to_roll is set.
 * Add initial support for Get/Put with user timestamps. Users can specify timestamps via ReadOptions and WriteOptions when calling DB::Get and DB::Put.
 * Accessing a partition of a partitioned filter or index through a pinned reference is no longer considered a cache hit.
+* The semantics of the per-block-type block read counts in the performance context now match those of the generic block_read_count.
+* Add C bindings for secondary instance, i.e. DBImplSecondary.
 
 ### New Features
 * Add an option `snap_refresh_nanos` (default to 0.1s) to periodically refresh the snapshot list in compaction jobs. Assign to 0 to disable the feature.

db/c.cc

@@ -517,6 +517,21 @@ rocksdb_t* rocksdb_open_for_read_only(
   return result;
 }
 
+rocksdb_t* rocksdb_open_as_secondary(const rocksdb_options_t* options,
+                                     const char* name,
+                                     const char* secondary_path,
+                                     char** errptr) {
+  DB* db;
+  if (SaveError(errptr,
+                DB::OpenAsSecondary(options->rep, std::string(name),
+                                    std::string(secondary_path), &db))) {
+    return nullptr;
+  }
+  rocksdb_t* result = new rocksdb_t;
+  result->rep = db;
+  return result;
+}
+
 rocksdb_backup_engine_t* rocksdb_backup_engine_open(
     const rocksdb_options_t* options, const char* path, char** errptr) {
   BackupEngine* be;
@@ -717,6 +732,37 @@ rocksdb_t* rocksdb_open_for_read_only_column_families(
   return result;
 }
 
+rocksdb_t* rocksdb_open_as_secondary_column_families(
+    const rocksdb_options_t* db_options, const char* name,
+    const char* secondary_path, int num_column_families,
+    const char** column_family_names,
+    const rocksdb_options_t** column_family_options,
+    rocksdb_column_family_handle_t** column_family_handles, char** errptr) {
+  std::vector<ColumnFamilyDescriptor> column_families;
+  for (int i = 0; i != num_column_families; ++i) {
+    column_families.emplace_back(
+        std::string(column_family_names[i]),
+        ColumnFamilyOptions(column_family_options[i]->rep));
+  }
+  DB* db;
+  std::vector<ColumnFamilyHandle*> handles;
+  if (SaveError(errptr, DB::OpenAsSecondary(DBOptions(db_options->rep),
+                                            std::string(name),
+                                            std::string(secondary_path),
+                                            column_families, &handles, &db))) {
+    return nullptr;
+  }
+  for (size_t i = 0; i != handles.size(); ++i) {
+    rocksdb_column_family_handle_t* c_handle =
+        new rocksdb_column_family_handle_t;
+    c_handle->rep = handles[i];
+    column_family_handles[i] = c_handle;
+  }
+  rocksdb_t* result = new rocksdb_t;
+  result->rep = db;
+  return result;
+}
+
 char** rocksdb_list_column_families(
     const rocksdb_options_t* options,
     const char* name,
@@ -3423,6 +3469,10 @@ void rocksdb_ingest_external_file_cf(
   SaveError(errptr, db->rep->IngestExternalFile(handle->rep, files, opt->rep));
 }
 
+void rocksdb_try_catch_up_with_primary(rocksdb_t* db, char** errptr) {
+  SaveError(errptr, db->rep->TryCatchUpWithPrimary());
+}
+
 rocksdb_slicetransform_t* rocksdb_slicetransform_create(
     void* state,
     void (*destructor)(void*),

db/c_test.c

@@ -45,6 +45,7 @@ static char sstfilename[200];
 static char dbbackupname[200];
 static char dbcheckpointname[200];
 static char dbpathname[200];
+static char secondary_path[200];
 
 static void StartPhase(const char* name) {
   fprintf(stderr, "=== Test %s\n", name);
@@ -1722,6 +1723,59 @@ int main(int argc, char** argv) {
     CheckNoError(err);
   }
 
+  // Check that secondary instance works.
+  StartPhase("open_as_secondary");
+  {
+    rocksdb_close(db);
+    rocksdb_destroy_db(options, dbname, &err);
+
+    rocksdb_options_t* db_options = rocksdb_options_create();
+    rocksdb_options_set_create_if_missing(db_options, 1);
+    db = rocksdb_open(db_options, dbname, &err);
+    CheckNoError(err);
+    rocksdb_t* db1;
+    rocksdb_options_t* opts = rocksdb_options_create();
+    rocksdb_options_set_max_open_files(opts, -1);
+    rocksdb_options_set_create_if_missing(opts, 1);
+    snprintf(secondary_path, sizeof(secondary_path),
+             "%s/rocksdb_c_test_secondary-%d", GetTempDir(), ((int)geteuid()));
+    db1 = rocksdb_open_as_secondary(opts, dbname, secondary_path, &err);
+    CheckNoError(err);
+
+    rocksdb_writeoptions_set_sync(woptions, 0);
+    rocksdb_writeoptions_disable_WAL(woptions, 1);
+    rocksdb_put(db, woptions, "key0", 4, "value0", 6, &err);
+    CheckNoError(err);
+    rocksdb_flushoptions_t* flush_opts = rocksdb_flushoptions_create();
+    rocksdb_flushoptions_set_wait(flush_opts, 1);
+    rocksdb_flush(db, flush_opts, &err);
+    CheckNoError(err);
+    rocksdb_try_catch_up_with_primary(db1, &err);
+    CheckNoError(err);
+    rocksdb_readoptions_t* ropts = rocksdb_readoptions_create();
+    rocksdb_readoptions_set_verify_checksums(ropts, 1);
+    rocksdb_readoptions_set_snapshot(ropts, NULL);
+    CheckGet(db, ropts, "key0", "value0");
+    CheckGet(db1, ropts, "key0", "value0");
+
+    rocksdb_writeoptions_disable_WAL(woptions, 0);
+    rocksdb_put(db, woptions, "key1", 4, "value1", 6, &err);
+    CheckNoError(err);
+    rocksdb_try_catch_up_with_primary(db1, &err);
+    CheckNoError(err);
+    CheckGet(db1, ropts, "key0", "value0");
+    CheckGet(db1, ropts, "key1", "value1");
+
+    rocksdb_close(db1);
+    rocksdb_destroy_db(opts, secondary_path, &err);
+    CheckNoError(err);
+
+    rocksdb_options_destroy(db_options);
+    rocksdb_options_destroy(opts);
+    rocksdb_readoptions_destroy(ropts);
+    rocksdb_flushoptions_destroy(flush_opts);
+  }
+
   // Simple sanity check that options setting db_paths work.
   StartPhase("open_db_paths");
   {

include/rocksdb/c.h

@@ -138,6 +138,10 @@ extern ROCKSDB_LIBRARY_API rocksdb_t* rocksdb_open_for_read_only(
     const rocksdb_options_t* options, const char* name,
     unsigned char error_if_log_file_exist, char** errptr);
 
+extern ROCKSDB_LIBRARY_API rocksdb_t* rocksdb_open_as_secondary(
+    const rocksdb_options_t* options, const char* name,
+    const char* secondary_path, char** errptr);
+
 extern ROCKSDB_LIBRARY_API rocksdb_backup_engine_t* rocksdb_backup_engine_open(
     const rocksdb_options_t* options, const char* path, char** errptr);
 
@@ -218,6 +222,13 @@ rocksdb_open_for_read_only_column_families(
     rocksdb_column_family_handle_t** column_family_handles,
     unsigned char error_if_log_file_exist, char** errptr);
 
+extern ROCKSDB_LIBRARY_API rocksdb_t* rocksdb_open_as_secondary_column_families(
+    const rocksdb_options_t* options, const char* name,
+    const char* secondary_path, int num_column_families,
+    const char** column_family_names,
+    const rocksdb_options_t** column_family_options,
+    rocksdb_column_family_handle_t** colummn_family_handles, char** errptr);
+
 extern ROCKSDB_LIBRARY_API char** rocksdb_list_column_families(
     const rocksdb_options_t* options, const char* name, size_t* lencf,
     char** errptr);
@@ -1375,6 +1386,9 @@ extern ROCKSDB_LIBRARY_API void rocksdb_ingest_external_file_cf(
     const char* const* file_list, const size_t list_len,
     const rocksdb_ingestexternalfileoptions_t* opt, char** errptr);
 
+extern ROCKSDB_LIBRARY_API void rocksdb_try_catch_up_with_primary(
+    rocksdb_t* db, char** errptr);
+
 /* SliceTransform */
 
 extern ROCKSDB_LIBRARY_API rocksdb_slicetransform_t*