Add method to log scheduling decision (#348)

* decisions: add method to debug print a decision

* tests: test print function in tests

include/faabric/batch-scheduler/SchedulingDecision.h

@@ -100,6 +100,8 @@ class SchedulingDecision
                     int32_t groupIdx);
 
     std::set<std::string> uniqueHosts();
+
+    void print();
 };
 
 }

src/batch-scheduler/SchedulingDecision.cpp

@@ -1,5 +1,6 @@
 #include <faabric/batch-scheduler/SchedulingDecision.h>
 #include <faabric/util/config.h>
+#include <faabric/util/logging.h>
 
 namespace faabric::batch_scheduler {
 
@@ -57,4 +58,22 @@ std::set<std::string> SchedulingDecision::uniqueHosts()
 {
     return std::set<std::string>(hosts.begin(), hosts.end());
 }
+
+void SchedulingDecision::print()
+{
+    SPDLOG_DEBUG("-------------- Decision for App: {} ----------------", appId);
+    SPDLOG_DEBUG("MsgId\tAppId\tGroupId\tGrIdx\tHostIp");
+    // Modulo a big number so that we can get the UUIDs to fit within one tab
+    int formatBase = 1e6;
+    for (int i = 0; i < hosts.size(); i++) {
+        SPDLOG_DEBUG("{}\t{}\t{}\t{}\t{}",
+                     messageIds.at(i) % formatBase,
+                     appId % formatBase,
+                     groupId % formatBase,
+                     groupIdxs.at(i),
+                     hosts.at(i));
+    }
+    SPDLOG_DEBUG("------------- End Decision for App {} ---------------",
+                 appId);
+}
 }

tests/test/batch-scheduler/test_scheduling_decisions.cpp

@@ -88,6 +88,9 @@ TEST_CASE_METHOD(ConfFixture, "Test building scheduling decisions", "[util]")
     REQUIRE(newDecision == decision);
     newDecision.groupId = 1338;
     REQUIRE(newDecision != decision);
+
+    // We can print scheduling decisions
+    REQUIRE_NOTHROW(decision.print());
 }
 
 TEST_CASE("Test converting point-to-point mappings to scheduling decisions",