From 1105538dd56dbb1b261d8b0ce8652f1dd719eaee Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 17 Oct 2024 09:05:04 +0200
Subject: Sketch CI common API changes

---
 mod/ci-common.cxx | 11 +++++++----
 mod/ci-common.hxx | 41 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 46 insertions(+), 6 deletions(-)

(limited to 'mod')

diff --git a/mod/ci-common.cxx b/mod/ci-common.cxx
index c0ef89f..b3fc432 100644
--- a/mod/ci-common.cxx
+++ b/mod/ci-common.cxx
@@ -534,14 +534,15 @@ namespace brep
     s.next ("", "");                         // End of manifest.
   }
 
-  optional<string> ci_start::
+  pair<optional<string>, ci_start::duplicate_tenant_result> ci_start::
   create (const basic_mark& error,
           const basic_mark&,
           const basic_mark* trace,
           odb::core::database& db,
           tenant_service&& service,
           duration notify_interval,
-          duration notify_delay) const
+          duration notify_delay,
+          duplicate_tenant_mode) const
   {
     using namespace odb::core;
 
@@ -556,7 +557,7 @@ namespace brep
     catch (const system_error& e)
     {
       error << "unable to generate request id: " << e;
-      return nullopt;
+      return {nullopt, duplicate_tenant_result::ignored}; // @@ TODO HACKED AROUND
     }
 
     // Use the generated request id if the tenant service id is not specified.
@@ -604,7 +605,7 @@ namespace brep
       *trace << "unloaded CI request " << t.id << " for service "
              << t.service->id << ' ' << t.service->type << " is created";
 
-    return move (t.id);
+    return {move (t.id), duplicate_tenant_result::created}; // @@ TODO HACKED AROUND
   }
 
   optional<ci_start::start_result> ci_start::
@@ -707,6 +708,8 @@ namespace brep
     if (t == nullptr)
       return nullopt;
 
+    // @@ Why not remove it if unloaded (and below)?
+
     optional<tenant_service> r (move (t->service));
     t->service = nullopt;
     t->archived = true;
diff --git a/mod/ci-common.hxx b/mod/ci-common.hxx
index 6a07154..d01e251 100644
--- a/mod/ci-common.hxx
+++ b/mod/ci-common.hxx
@@ -72,16 +72,39 @@ namespace brep
     // created tenant and set the initial delay for the first notification.
     // See also the build_unloaded() tenant services notification.
     //
+    // The duplicate_tenant_mode argument specifies the behavior in case of
+    // the duplicate tenant_service type/id pair. The default is to fail by
+    // throwing an exception. Alternatively, this can be ignored or the
+    // previous tenant can be canceled (thus freeing the type/id pair; see
+    // below) and a new tenant with the same type/id created. In both these
+    // modes (ignore and replace), the second half of the returned pair
+    // indicates whether there was a duplicate. If there were, then for the
+    // ignore mode the returned reference corresponds to the old tenant and
+    // for the replace mode -- to the new tenant.
+    //
+    // The replace_archived mode is a variant of replace that replaces if the
+    // tenant is already archived and ignores it otherwise (with the result
+    // having the same semantics as in the replace and ignore modes).
+    //
+    // Note also that the duplicate_tenant_mode::replace modes are not the
+    // same as separate calls to create() and then to cancel() since the
+    // latter would happen in two separate transactions and will thus be
+    // racy. @@@ TODO
+    //
     // Note: should be called out of the database transaction.
     //
-    optional<string>
+    enum class duplicate_tenant_mode {fail, ignore, replace, replace_archived};
+    enum class duplicate_tenant_result {created, ignored, replaced};
+
+    pair<optional<string>, duplicate_tenant_result>
     create (const basic_mark& error,
             const basic_mark& warn,
             const basic_mark* trace,
             odb::core::database&,
             tenant_service&&,
             duration notify_interval,
-            duration notify_delay) const;
+            duration notify_delay,
+            duplicate_tenant_mode = duplicate_tenant_mode::fail) const;
 
     // Load (and start) previously created (as unloaded) CI request. Similarly
     // to the start() function, return nullopt on an internal error.
@@ -101,6 +124,12 @@ namespace brep
     // Cancel previously created or started CI request. Return the service
     // state or nullopt if there is no tenant for such a type/id pair.
     //
+    // Specifically, this function clears the tenant service state (thus
+    // allowing reusing the same service type/id pair in another tenant) and
+    // archives the tenant, unless the tenant is unloaded, in which case it is
+    // dropped (@@@ TODO). Note that the latter allow using unloaded tenants
+    // as a relatively cheap asynchronous execution mechanism.
+    //
     // Note: should be called out of the database transaction.
     //
     optional<tenant_service>
@@ -115,6 +144,14 @@ namespace brep
     // is no tenant for the specified tenant id. Note that the reason argument
     // is only used for tracing.
     //
+    // @@@ Is tenant id here and reference above the same thing? Maybe use
+    //     "tenant id" and "service id" terminology throughout?
+    //
+    // Similarly to above, this function archives the tenant, unless the
+    // tenant is unloaded, in which case it is dropped (@@@ TODO). Note,
+    // however, that this version does not touch the service state (use the
+    // above version if you want to clear it).
+    //
     // Note: should be called out of the database transaction.
     //
     bool
-- 
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