From 5aa1b62fafc20424cf3d4052f60e69a4e7e62597 Mon Sep 17 00:00:00 2001
From: Thijs Cadier <thijs@appsignal.com>
Date: Sun, 4 Oct 2015 13:30:45 +0200
Subject: [PATCH] Use an Arc to share ClientPool between threads

---
 src/client.rs   | 44 +++++++++++++++++---------------------------
 tests/client.rs |  3 ++-
 tests/cursor.rs |  3 ++-
 3 files changed, 21 insertions(+), 29 deletions(-)

diff --git a/src/client.rs b/src/client.rs
index f8ce7a0..98f1dcb 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -20,14 +20,18 @@ use super::database::Database;
 use super::uri::Uri;
 use super::read_prefs::ReadPrefs;
 
-// TODO: We're using a sort of poor man's Arc here
-// with this root bool, there must be a better way.
+/// Client pool to a MongoDB cluster.
+///
+/// This client pool cannot be cloned, but it can be shared between threads by using an `Arc`.
+/// Use the pool to pop a client and do operations. The client will be automatically added
+/// back to the pool when it goes out of scope.
+///
+/// See: http://api.mongodb.org/c/current/mongoc_client_pool_t.html
 pub struct ClientPool {
-    root_instance: bool,
-    // Uri and SslOptions need to be present for the
-    // lifetime of this pool.
+    // Uri and SslOptions need to be present for the lifetime of this pool otherwise the C driver
+    // loses access to resources it needs.
     uri:          Uri,
-    ssl_options:  Option<SslOptions>,
+    _ssl_options: Option<SslOptions>,
     inner:         *mut bindings::mongoc_client_pool_t
 }
 
@@ -55,10 +59,9 @@ impl ClientPool {
             None => ()
         };
         ClientPool {
-            root_instance: true,
-            uri:         uri,
-            ssl_options: ssl_options,
-            inner:       pool
+            uri:          uri,
+            _ssl_options: ssl_options,
+            inner:        pool
         }
     }
 
@@ -82,6 +85,7 @@ impl ClientPool {
     /// See: http://api.mongodb.org/c/current/mongoc_client_pool_push.html
     unsafe fn push(&self, mongo_client: *mut bindings::mongoc_client_t) {
         assert!(!self.inner.is_null());
+        assert!(!mongo_client.is_null());
         bindings::mongoc_client_pool_push(
             self.inner,
             mongo_client
@@ -98,25 +102,11 @@ impl fmt::Debug for ClientPool {
     }
 }
 
-impl Clone for ClientPool {
-    fn clone(&self) -> ClientPool {
-        assert!(!self.inner.is_null());
-        ClientPool {
-            root_instance: false,
-            uri:           self.uri.clone(),
-            ssl_options:   self.ssl_options.clone(),
-            inner:         self.inner.clone()
-        }
-    }
-}
-
 impl Drop for ClientPool {
     fn drop(&mut self) {
-        if self.root_instance {
-            assert!(!self.inner.is_null());
-            unsafe {
-                bindings::mongoc_client_pool_destroy(self.inner);
-            }
+        assert!(!self.inner.is_null());
+        unsafe {
+            bindings::mongoc_client_pool_destroy(self.inner);
         }
     }
 }
diff --git a/tests/client.rs b/tests/client.rs
index 792f8d3..9959ef5 100644
--- a/tests/client.rs
+++ b/tests/client.rs
@@ -1,5 +1,6 @@
 use std::env;
 use std::path::PathBuf;
+use std::sync::Arc;
 use std::thread;
 
 use mongo_driver::uri::Uri;
@@ -51,7 +52,7 @@ fn test_new_pool_pop_client_and_take_database_and_collection() {
 #[test]
 fn test_new_pool_and_pop_client_in_threads() {
     let uri = Uri::new("mongodb://localhost:27017/").unwrap();
-    let pool = ClientPool::new(uri, None);
+    let pool = Arc::new(ClientPool::new(uri, None));
 
     let pool1 = pool.clone();
     let guard1 = thread::spawn(move || {
diff --git a/tests/cursor.rs b/tests/cursor.rs
index 382fb5d..d12876b 100644
--- a/tests/cursor.rs
+++ b/tests/cursor.rs
@@ -1,3 +1,4 @@
+use std::sync::Arc;
 use std::thread;
 
 use bson;
@@ -34,7 +35,7 @@ fn test_tailing_cursor() {
     // See: http://api.mongodb.org/c/1.1.8/cursors.html#tailable
 
     let uri      = Uri::new("mongodb://localhost:27017/").unwrap();
-    let pool     = ClientPool::new(uri, None);
+    let pool     = Arc::new(ClientPool::new(uri, None));
     let client   = pool.pop();
     let database = client.get_database("rust_test");
     database.get_collection("capped").drop().unwrap_or(());