From a7e766e1aa77fff846d8426658befd9a01fe2861 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 11 Aug 2015 15:34:12 +0200
Subject: Share DB object between modules

---
 brep/buildfile           |  3 ++-
 brep/search.cxx          |  9 ++-------
 brep/shared-database     | 24 ++++++++++++++++++++++++
 brep/shared-database.cxx | 41 +++++++++++++++++++++++++++++++++++++++++
 brep/view.cxx            |  9 ++-------
 build.sh                 |  2 +-
 6 files changed, 72 insertions(+), 16 deletions(-)
 create mode 100644 brep/shared-database
 create mode 100644 brep/shared-database.cxx

diff --git a/brep/buildfile b/brep/buildfile
index 13e1d20..5340d22 100644
--- a/brep/buildfile
+++ b/brep/buildfile
@@ -14,7 +14,8 @@ brep = cxx{package package-odb}
 libso{brep}: $brep $libs
 libso{brep}: cxx.export.poptions = -I$out_root -I$src_root
 
-brep = cxx{diagnostics module services search view} cli.cxx{options}
+brep = cxx{diagnostics module services search view shared-database} \
+       cli.cxx{options}
 web = ../web/apache/cxx{request service}
 libso{brep-apache}: $brep $web libso{brep} $libs
 
diff --git a/brep/search.cxx b/brep/search.cxx
index fc86284..3aa6503 100644
--- a/brep/search.cxx
+++ b/brep/search.cxx
@@ -12,14 +12,13 @@
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
 
-#include <odb/pgsql/database.hxx>
-
 #include <butl/path>
 
 #include <web/module>
 
 #include <brep/package>
 #include <brep/package-odb>
+#include <brep/shared-database>
 
 using namespace std;
 using namespace odb::core;
@@ -35,11 +34,7 @@ namespace brep
                                             cli::unknown_mode::fail,
                                             cli::unknown_mode::fail);
 
-    db_ = make_shared<odb::pgsql::database> ("",
-                                             "",
-                                             "brep",
-                                             options_->db_host (),
-                                             options_->db_port ());
+    db_ = shared_database (options_->db_host (), options_->db_port ());
 
     if (options_->results_on_page () > 30)
       fail << "too many search results on page: "
diff --git a/brep/shared-database b/brep/shared-database
new file mode 100644
index 0000000..cad526f
--- /dev/null
+++ b/brep/shared-database
@@ -0,0 +1,24 @@
+// file      : brep/shared-database -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BREP_SHARED_DATABASE
+#define BREP_SHARED_DATABASE
+
+#include <string>
+#include <memory> // shared_ptr
+
+#include <odb/forward.hxx> // database
+
+namespace brep
+{
+  // Returns pointer to the shared database instance, creating one on the
+  // first call. On subsequent calls ensures passed host and port equals
+  // to ones of the shared database instance throwing runtime_error otherwise.
+  // Is not thread-safe.
+  //
+  std::shared_ptr<odb::core::database>
+  shared_database (const std::string& host, unsigned int port);
+}
+
+#endif // BREP_SHARED_DATABASE
diff --git a/brep/shared-database.cxx b/brep/shared-database.cxx
new file mode 100644
index 0000000..fb952d8
--- /dev/null
+++ b/brep/shared-database.cxx
@@ -0,0 +1,41 @@
+// file      : brep/shared-database.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <brep/shared-database>
+
+#include <memory>    // weak_ptr, shared_ptr, make_shared()
+#include <stdexcept> // runtime_error
+
+#include <odb/pgsql/database.hxx>
+
+using namespace std;
+using namespace odb;
+
+namespace brep
+{
+  shared_ptr<database>
+  shared_database (const string& host, unsigned int port)
+  {
+    static weak_ptr<pgsql::database> db;
+
+    // In C++11, function-static variable initialization is
+    // guaranteed to be thread-safe, thought this doesn't
+    // seem to be enough in our case (because we are re-
+    // initializing the weak pointer).
+    //
+    if (shared_ptr<database> d = db.lock ())
+    {
+      if (h != d->host () || p != d->port ())
+        throw runtime_error ("shared database host/port mismatch");
+
+      return d;
+    }
+    else
+    {
+      d = make_shared<database> ("", "", "brep", h, p);
+      db = d;
+      return d;
+    }
+  }
+}
diff --git a/brep/view.cxx b/brep/view.cxx
index 08e2592..2f3bd17 100644
--- a/brep/view.cxx
+++ b/brep/view.cxx
@@ -11,12 +11,11 @@
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
 
-#include <odb/pgsql/database.hxx>
-
 #include <web/module>
 
 #include <brep/package>
 #include <brep/package-odb>
+#include <brep/shared-database>
 
 using namespace std;
 using namespace odb::core;
@@ -31,11 +30,7 @@ namespace brep
                                           cli::unknown_mode::fail,
                                           cli::unknown_mode::fail);
 
-    db_ = make_shared<odb::pgsql::database> ("",
-                                             "",
-                                             "brep",
-                                             options_->db_host (),
-                                             options_->db_port ());
+    db_ = shared_database (options_->db_host (), options_->db_port ());
   }
 
   void view::
diff --git a/build.sh b/build.sh
index 0ce4ae3..3d06a80 100755
--- a/build.sh
+++ b/build.sh
@@ -30,7 +30,7 @@ cli --include-with-brackets --include-prefix brep  --hxx-suffix "" \
 echo "g++ libbrep-apache.so"
 
 s="search.cxx view.cxx module.cxx diagnostics.cxx services.cxx options.cxx \
-../web/apache/request.cxx ../web/apache/service.cxx"
+shared-database.cxx ../web/apache/request.cxx ../web/apache/service.cxx"
 
 g++ -shared $DEBUG -std=c++11 -I. -I/usr/include/apr-1 -I/usr/include/httpd \
     -I.. -I../../libbpkg -I../../libbutl -L. -L../../libbpkg/bpkg \
-- 
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