Add support for tenant service reference count

10 files changed, 88 insertions, 20 deletions

diff --git a/libbrep/build-extra.sql b/libbrep/build-extra.sql
index 0c0f010..3134fbb 100644
--- a/libbrep/build-extra.sql
+++ b/libbrep/build-extra.sql
@@ -50,6 +50,7 @@ CREATE FOREIGN TABLE build_tenant (
   archived BOOLEAN NOT NULL,
   service_id TEXT NULL,
   service_type TEXT NULL,
+  service_ref_count BIGINT NULL,
   service_data TEXT NULL,
   unloaded_timestamp BIGINT NULL,
   unloaded_notify_interval BIGINT NULL,
diff --git a/libbrep/build.hxx b/libbrep/build.hxx
index b485636..5ebbb0c 100644
--- a/libbrep/build.hxx
+++ b/libbrep/build.hxx
@@ -28,7 +28,7 @@
 //
 #define LIBBREP_BUILD_SCHEMA_VERSION_BASE 28
 
-#pragma db model version(LIBBREP_BUILD_SCHEMA_VERSION_BASE, 28, closed)
+#pragma db model version(LIBBREP_BUILD_SCHEMA_VERSION_BASE, 29, closed)
 
 // We have to keep these mappings at the global scope instead of inside the
 // brep namespace because they need to be also effective in the bbot namespace
diff --git a/libbrep/build.xml b/libbrep/build.xml
index d58e5f4..284db49 100644
--- a/libbrep/build.xml
+++ b/libbrep/build.xml
@@ -1,4 +1,6 @@
 <changelog xmlns="http://www.codesynthesis.com/xmlns/odb/changelog" database="pgsql" schema-name="build" version="1">
+  <changeset version="29"/>
+
   <model version="28">
     <table name="build" kind="object">
       <column name="package_tenant" type="TEXT" null="false"/>
diff --git a/libbrep/common.hxx b/libbrep/common.hxx
index d2009f5..22302f3 100644
--- a/libbrep/common.hxx
+++ b/libbrep/common.hxx
@@ -543,17 +543,22 @@ namespace brep
   //
   // Note that the {id, type} pair must be unique.
   //
+  // The reference count is used to keep track of the number of attempts to
+  // create a duplicate tenant with this {id, type} (see ci_start::create()
+  // for details).
+  //
   #pragma db value
   struct tenant_service
   {
     string id;
     string type;
+    uint64_t ref_count;
     optional<string> data;
 
     tenant_service () = default;
 
     tenant_service (string i, string t, optional<string> d = nullopt)
-        : id (move (i)), type (move (t)), data (move (d)) {}
+        : id (move (i)), type (move (t)), ref_count (1), data (move (d)) {}
   };
 
   // Version comparison operators.
diff --git a/libbrep/package.hxx b/libbrep/package.hxx
index 79b2c68..2714d10 100644
--- a/libbrep/package.hxx
+++ b/libbrep/package.hxx
@@ -20,7 +20,7 @@
 //
 #define LIBBREP_PACKAGE_SCHEMA_VERSION_BASE 34
 
-#pragma db model version(LIBBREP_PACKAGE_SCHEMA_VERSION_BASE, 35, closed)
+#pragma db model version(LIBBREP_PACKAGE_SCHEMA_VERSION_BASE, 36, closed)
 
 namespace brep
 {
diff --git a/libbrep/package.xml b/libbrep/package.xml
index 8b6c706..ac48ec4 100644
--- a/libbrep/package.xml
+++ b/libbrep/package.xml
@@ -1,4 +1,10 @@
 <changelog xmlns="http://www.codesynthesis.com/xmlns/odb/changelog" database="pgsql" schema-name="package" version="1">
+  <changeset version="36">
+    <alter-table name="tenant">
+      <add-column name="service_ref_count" type="BIGINT" null="true"/>
+    </alter-table>
+  </changeset>
+
   <changeset version="35">
     <alter-table name="package">
       <add-column name="reviews_pass" type="BIGINT" null="true"/>
diff --git a/migrate/migrate.cxx b/migrate/migrate.cxx
index 090fcac..095e6a3 100644
--- a/migrate/migrate.cxx
+++ b/migrate/migrate.cxx
@@ -208,7 +208,6 @@ create (database& db, bool extra_only) const
 
 // Register the data migration functions for the package database schema.
 //
-#if 0
 template <schema_version v>
 using package_migration_entry_base =
   data_migration_entry<v, LIBBREP_PACKAGE_SCHEMA_VERSION_BASE>;
@@ -220,11 +219,14 @@ struct package_migration_entry: package_migration_entry_base<v>
       : package_migration_entry_base<v> (f, "package") {}
 };
 
-static const package_migration_entry<26>
-package_migrate_v26 ([] (database& db)
+static const package_migration_entry<36>
+package_migrate_v36 ([] (database& db)
 {
+  // Set the reference count to 1 for tenant associated services.
+  //
+  db.execute ("UPDATE tenant SET service_ref_count = 1 "
+              "WHERE service_id IS NOT NULL");
 });
-#endif
 
 // Register the data migration functions for the build database schema.
 //
diff --git a/mod/ci-common.cxx b/mod/ci-common.cxx
index 4b9f9f9..cba421b 100644
--- a/mod/ci-common.cxx
+++ b/mod/ci-common.cxx
@@ -553,7 +553,11 @@ namespace brep
     assert (!transaction::has_current ());
 
     build_tenant t;
+
+    // Set the reference count to 1 for the `created` result.
+    //
     duplicate_tenant_result r (duplicate_tenant_result::created);
+    service.ref_count = 1;
 
     for (string request_id;;)
     {
@@ -584,14 +588,31 @@ namespace brep
                       : duplicate_tenant_mode::ignore);
             }
 
+            // Shouldn't be here otherwise.
+            //
+            assert (t->service);
+
             // Bail out in the ignore mode and cancel the tenant in the
             // replace mode.
             //
             if (mode == duplicate_tenant_mode::ignore)
+            {
+              // Increment the reference count for the `ignored` result.
+              //
+              ++(t->service->ref_count);
+
+              db.update (t);
+              tr.commit ();
+
               return make_pair (move (t->id), duplicate_tenant_result::ignored);
+            }
 
             assert (mode == duplicate_tenant_mode::replace);
 
+            // Preserve the current reference count for the `replaced` result.
+            //
+            service.ref_count = t->service->ref_count;
+
             if (t->unloaded_timestamp)
             {
               db.erase (t);
@@ -678,6 +699,7 @@ namespace brep
         //
         request_id = move (t.id);
         service = move (*t.service);
+        service.ref_count = 1;
         r = duplicate_tenant_result::created;
       }
     }
@@ -788,7 +810,8 @@ namespace brep
           odb::core::database& db,
           size_t retry,
           const string& type,
-          const string& id) const
+          const string& id,
+          bool ref_count) const
   {
     using namespace odb::core;
 
@@ -810,25 +833,44 @@ namespace brep
         if (t == nullptr)
           return nullopt;
 
-        r = move (t->service);
+        // Shouldn't be here otherwise.
+        //
+        assert (t->service && t->service->ref_count != 0);
 
-        if (t->unloaded_timestamp)
+        bool cancel (!ref_count || --(t->service->ref_count) == 0);
+
+        if (cancel)
         {
-          db.erase (t);
+          // Move out the service state before it is dropped from the tenant.
+          //
+          r = move (t->service);
+
+          if (t->unloaded_timestamp)
+          {
+            db.erase (t);
+          }
+          else
+          {
+            t->service = nullopt;
+            t->archived = true;
+            db.update (t);
+          }
+
+          if (trace != nullptr)
+            *trace << "CI request " << t->id << " for service " << id << ' '
+                   << type << " is canceled";
         }
         else
         {
-          t->service = nullopt;
-          t->archived = true;
-          db.update (t);
+          db.update (t); // Update the service reference count.
+
+          // Move out the service state after the tenant is updated.
+          //
+          r = move (t->service);
         }
 
         tr.commit ();
 
-        if (trace != nullptr)
-          *trace << "CI request " << t->id << " for service " << id << ' '
-                 << type << " is canceled";
-
         // Bail out if we have successfully updated or erased the tenant
         // object.
         //
diff --git a/mod/ci-common.hxx b/mod/ci-common.hxx
index 36d5f0e..b32d397 100644
--- a/mod/ci-common.hxx
+++ b/mod/ci-common.hxx
@@ -103,6 +103,10 @@ namespace brep
     // Finally note that only duplicate_tenant_mode::fail can be used if the
     // service id is empty.
     //
+    // The tenant reference count is set to 1 if the result is `created`,
+    // incremented if the result is `ignored`, and preserved if the result is
+    // `replaced`.
+    //
     // Repeat the attempts on the recoverable database failures (deadlocks,
     // etc) and throw runtime_error if no more retries left.
     //
@@ -150,6 +154,11 @@ namespace brep
     // dropped. Note that the latter allow using unloaded tenants as a
     // relatively cheap asynchronous execution mechanism.
     //
+    // If ref_count is true, then decrement the tenant reference count and
+    // only cancel the CI request if it becomes 0. In this mode the caller can
+    // determine if the request was actually canceled by checking if the
+    // reference count in the returned service state is 0.
+    //
     // Repeat the attempts on the recoverable database failures (deadlocks,
     // etc) and throw runtime_error if no more retries left.
     //
@@ -162,7 +171,8 @@ namespace brep
             odb::core::database&,
             size_t retry,
             const string& type,
-            const string& id) const;
+            const string& id,
+            bool ref_count = false) const;
 
     // Cancel previously created or started CI request. Return false if there
     // is no tenant for the specified tenant id. Note that the reason argument
diff --git a/mod/mod-ci-github.cxx b/mod/mod-ci-github.cxx
index 9d2606b..ba80ed6 100644
--- a/mod/mod-ci-github.cxx
+++ b/mod/mod-ci-github.cxx
@@ -828,7 +828,7 @@ namespace brep
 
     if (system_clock::now () > sd.installation_access.expires_at)
     {
-      if (new_iat = get_iat ())
+      if ((new_iat = get_iat ()))
         iat = &*new_iat;
       else
         throw server_error ();