Share environment between RocksDB instances

Allow multiple RocksDB instance in the same process to share resources instead of fighting to get them.

lib/Cargo.toml

@@ -38,6 +38,7 @@ hex = "0.4"
 nom = "7"
 siphasher = "0.3"
 lasso = "0.5"
+lazy_static = "1"
 sophia_api = { version = "0.7", optional = true }
 json-event-parser = "0.1"
 num_cpus = "1"

lib/src/storage/backend/rocksdb.rs

@@ -6,6 +6,7 @@
 
 use crate::error::invalid_input_error;
 use crate::storage::backend::{CompactionAction, CompactionFilter};
+use lazy_static::lazy_static;
 use libc::{self, c_char, c_int, c_uchar, c_void, free, size_t};
 use oxrocksdb_sys::*;
 use rand::random;
@@ -13,6 +14,7 @@ use std::borrow::Borrow;
 use std::cell::Cell;
 use std::env::temp_dir;
 use std::ffi::{CStr, CString};
+use std::fs::remove_dir_all;
 use std::io::{Error, ErrorKind, Result};
 use std::iter::Zip;
 use std::ops::Deref;
@@ -43,6 +45,23 @@ macro_rules! ffi_result_impl {
     }}
 }
 
+lazy_static! {
+    static ref ROCKSDB_ENV: UnsafeEnv = {
+        unsafe {
+            let env = rocksdb_create_default_env();
+            assert!(!env.is_null(), "rocksdb_create_default_env returned null");
+            UnsafeEnv(env)
+        }
+    };
+    static ref ROCKSDB_MEM_ENV: UnsafeEnv = {
+        unsafe {
+            let env = rocksdb_create_mem_env();
+            assert!(!env.is_null(), "rocksdb_create_mem_env returned null");
+            UnsafeEnv(env)
+        }
+    };
+}
+
 pub struct ColumnFamilyDefinition {
     pub name: &'static str,
     pub merge_operator: Option<MergeOperator>,
@@ -69,12 +88,12 @@ struct DbHandler {
     ingest_external_file_options: *mut rocksdb_ingestexternalfileoptions_t,
     compaction_options: *mut rocksdb_compactoptions_t,
     block_based_table_options: *mut rocksdb_block_based_table_options_t,
-    env: Option<*mut rocksdb_env_t>,
     column_family_names: Vec<&'static str>,
     cf_handles: Vec<*mut rocksdb_column_family_handle_t>,
     cf_options: Vec<*mut rocksdb_options_t>,
     cf_compaction_filters: Vec<*mut rocksdb_compactionfilter_t>,
     path: PathBuf,
+    remove_path: bool,
 }
 
 impl Drop for DbHandler {
@@ -97,13 +116,13 @@ impl Drop for DbHandler {
             rocksdb_transactiondb_options_destroy(self.transactiondb_options);
             rocksdb_options_destroy(self.options);
             rocksdb_block_based_options_destroy(self.block_based_table_options);
-            if let Some(env) = self.env {
-                rocksdb_env_destroy(env);
-            }
             for cf_compact in &self.cf_compaction_filters {
                 rocksdb_compactionfilter_destroy(*cf_compact);
             }
         }
+        if self.remove_path && self.path.exists() {
+            remove_dir_all(&self.path).unwrap();
+        }
     }
 }
 
@@ -114,20 +133,24 @@ impl Db {
         } else {
             temp_dir()
         }
-        .join("oxigraph-temp-rocksdb");
-        Ok(Self(Arc::new(Self::do_open(&path, column_families, true)?)))
+        .join(format!("oxigraph-rocksdb-{}", random::<u128>()));
+        Ok(Self(Arc::new(Self::do_open(path, column_families, true)?)))
     }
 
     pub fn open(path: &Path, column_families: Vec<ColumnFamilyDefinition>) -> Result<Self> {
-        Ok(Self(Arc::new(Self::do_open(path, column_families, false)?)))
+        Ok(Self(Arc::new(Self::do_open(
+            path.to_owned(),
+            column_families,
+            false,
+        )?)))
     }
 
     fn do_open(
-        path: &Path,
+        path: PathBuf,
         mut column_families: Vec<ColumnFamilyDefinition>,
         in_memory: bool,
     ) -> Result<DbHandler> {
-        let c_path = path_to_cstring(path)?;
+        let c_path = path_to_cstring(&path)?;
 
         unsafe {
             let options = rocksdb_options_create();
@@ -150,6 +173,14 @@ impl Db {
                 .try_into()
                 .unwrap(),
             );
+            rocksdb_options_set_env(
+                options,
+                if in_memory {
+                    ROCKSDB_MEM_ENV.0
+                } else {
+                    ROCKSDB_ENV.0
+                },
+            );
             let block_based_table_options = rocksdb_block_based_options_create();
             assert!(
                 !block_based_table_options.is_null(),
@@ -168,19 +199,6 @@ impl Db {
                 "rocksdb_transactiondb_options_create returned null"
             );
 
-            let env = if in_memory {
-                let env = rocksdb_create_mem_env();
-                if env.is_null() {
-                    rocksdb_options_destroy(options);
-                    rocksdb_transactiondb_options_destroy(transactiondb_options);
-                    return Err(other_error("Not able to create an in-memory environment."));
-                }
-                rocksdb_options_set_env(options, env);
-                Some(env)
-            } else {
-                None
-            };
-
             if !column_families.iter().any(|c| c.name == "default") {
                 column_families.push(ColumnFamilyDefinition {
                     name: "default",
@@ -327,12 +345,12 @@ impl Db {
                 ingest_external_file_options,
                 compaction_options,
                 block_based_table_options,
-                env,
                 column_family_names,
                 cf_handles,
                 cf_options,
                 cf_compaction_filters,
-                path: path.to_path_buf(),
+                path,
+                remove_path: in_memory,
             })
         }
     }
@@ -1075,6 +1093,11 @@ unsafe extern "C" fn compactionfilter_name(filter: *mut c_void) -> *const c_char
     filter.name.as_ptr()
 }
 
+struct UnsafeEnv(*mut rocksdb_env_t);
+
+// Hack for lazy_static. OK because only written in lazy static and used in a thread-safe way by RocksDB
+unsafe impl Sync for UnsafeEnv {}
+
 fn path_to_cstring(path: &Path) -> Result<CString> {
     CString::new(
         path.to_str()