From 475771f84d3fb6197fea772d67e5a59c46b512e5 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 20 Nov 2024 15:17:26 +0200
Subject: Add support for tenant service reference count

---
 mod/ci-common.cxx     | 64 ++++++++++++++++++++++++++++++++++++++++++---------
 mod/ci-common.hxx     | 12 +++++++++-
 mod/mod-ci-github.cxx |  2 +-
 3 files changed, 65 insertions(+), 13 deletions(-)

(limited to 'mod')

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 ();
-- 
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