hydra-queue-runner: Detect changes to the scheduling shares

src/hydra-queue-runner/queue-monitor.cc

@@ -26,6 +26,7 @@ void State::queueMonitorLoop()
     receiver buildsCancelled(*conn, "builds_cancelled");
     receiver buildsDeleted(*conn, "builds_deleted");
     receiver buildsBumped(*conn, "builds_bumped");
+    receiver jobsetSharesChanged(*conn, "jobset_shares_changed");
 
     auto store = openStore(); // FIXME: pool
 
@@ -49,6 +50,10 @@ void State::queueMonitorLoop()
             printMsg(lvlTalkative, "got notification: builds cancelled or bumped");
             processQueueChange(*conn);
         }
+        if (jobsetSharesChanged.get()) {
+            printMsg(lvlTalkative, "got notification: jobset shares changed");
+            processJobsetSharesChange(*conn);
+        }
     }
 }
 
@@ -410,12 +415,13 @@ Step::ptr State::createStep(std::shared_ptr<StoreAPI> store, const Path & drvPat
 Jobset::ptr State::createJobset(pqxx::work & txn,
     const std::string & projectName, const std::string & jobsetName)
 {
-    auto jobsets_(jobsets.lock());
-
     auto p = std::make_pair(projectName, jobsetName);
 
+    {
+        auto jobsets_(jobsets.lock());
         auto i = jobsets_->find(p);
         if (i != jobsets_->end()) return i->second;
+    }
 
     auto res = txn.parameterized
         ("select schedulingShares from Jobsets where project = $1 and name = $2")
@@ -423,9 +429,9 @@ Jobset::ptr State::createJobset(pqxx::work & txn,
     if (res.empty()) throw Error("missing jobset - can't happen");
 
     auto shares = res[0]["schedulingShares"].as<unsigned int>();
-    if (shares == 0) shares = 1;
 
-    auto jobset = std::make_shared<Jobset>(shares);
+    auto jobset = std::make_shared<Jobset>();
+    jobset->setShares(shares);
 
     /* Load the build steps from the last 24 hours. */
     res = txn.parameterized
@@ -438,6 +444,23 @@ Jobset::ptr State::createJobset(pqxx::work & txn,
         jobset->addStep(startTime, stopTime - startTime);
     }
 
+    auto jobsets_(jobsets.lock());
+    // Can't happen because only this thread adds to "jobsets".
+    assert(jobsets_->find(p) == jobsets_->end());
     (*jobsets_)[p] = jobset;
     return jobset;
 }
+
+
+void State::processJobsetSharesChange(Connection & conn)
+{
+    /* Get the current set of jobsets. */
+    pqxx::work txn(conn);
+    auto res = txn.exec("select project, name, schedulingShares from Jobsets");
+    for (auto const & row : res) {
+        auto jobsets_(jobsets.lock());
+        auto i = jobsets_->find(std::make_pair(row["project"].as<string>(), row["name"].as<string>()));
+        if (i == jobsets_->end()) continue;
+        i->second->setShares(row["schedulingShares"].as<unsigned int>());
+    }
+}

src/hydra-queue-runner/state.hh

@@ -67,14 +67,12 @@ public:
     typedef std::shared_ptr<Jobset> ptr;
     typedef std::weak_ptr<Jobset> wptr;
 
-    Jobset(unsigned int shares) : shares(shares) { }
-
     static const time_t schedulingWindow = 24 * 60 * 60;
 
 private:
 
     std::atomic<time_t> seconds{0};
-    std::atomic<unsigned int> shares;
+    std::atomic<unsigned int> shares{1};
 
     /* The start time and duration of the most recent build steps. */
     Sync<std::map<time_t, time_t>> steps;
@@ -86,6 +84,12 @@ public:
         return (double) seconds / shares;
     }
 
+    void setShares(int shares_)
+    {
+        assert(shares_ > 0);
+        shares = shares_;
+    }
+
     time_t getSeconds() { return seconds; }
 
     void addStep(time_t startTime, time_t duration);
@@ -354,6 +358,8 @@ private:
     Jobset::ptr createJobset(pqxx::work & txn,
         const std::string & projectName, const std::string & jobsetName);
 
+    void processJobsetSharesChange(Connection & conn);
+
     void makeRunnable(Step::ptr step);
 
     /* The thread that selects and starts runnable builds. */

src/sql/hydra.sql

@@ -64,6 +64,7 @@ create table Jobsets (
     checkInterval integer not null default 300, -- minimum time in seconds between polls (0 = disable polling)
     schedulingShares integer not null default 100,
     fetchErrorMsg text,
+    check schedulingShares > 0,
     primary key   (project, name),
     foreign key   (project) references Projects(name) on delete cascade on update cascade
 #ifdef SQLITE
@@ -72,6 +73,14 @@ create table Jobsets (
 #endif
 );
 
+#ifdef POSTGRESQL
+
+create function notifyJobsetSharesChanged() returns trigger as 'begin notify jobset_shares_changed; return null; end;' language plpgsql;
+create trigger JobsetSharesChanged after update on Jobsets for each row
+  when (old.schedulingShares != new.schedulingShares) execute procedure notifyJobsetSharesChanged();
+
+#endif
+
 
 create table JobsetRenames (
     project       text not null,

src/sql/upgrade-41.sql

@@ -0,0 +1,5 @@
+create function notifyJobsetSharesChanged() returns trigger as 'begin notify jobset_shares_changed; return null; end;' language plpgsql;
+create trigger JobsetSharesChanged after update on Jobsets for each row
+  when (old.schedulingShares != new.schedulingShares) execute procedure notifyJobsetSharesChanged();
+
+alter table Jobsets add constraint jobsets_check check (schedulingShares > 0);