[ML] do not fail to start analytics process if memory estimate is lower than predicted memory usage (#1465)

From the management side, we allow users to update configured memory limits after the analytics configuration has started.

To help users with their workflow, we should allow analytics processes to attempt to run even if the configured memory limit is lower than our memory estimate. 


related to: elastic/elasticsearch#61505

Author: benwtrent

lib/api/CDataFrameAnalysisRunner.cc

@@ -99,14 +99,14 @@ void CDataFrameAnalysisRunner::computeAndSaveExecutionStrategy() {
         auto roundMb = [](std::size_t memory) {
             return 0.01 * static_cast<double>((100 * memory) / BYTES_IN_MB);
         };
-
-        // Report rounded up to the nearest MB.
-        HANDLE_FATAL(<< "Input error: memory limit " << roundMb(memoryLimit)
-                     << "MB is too low to perform analysis. You need to give the process"
-                     << " at least " << std::ceil(roundMb(memoryUsage))
-                     << "MB, but preferably more.");
-
-    } else if (m_NumberPartitions > 1) {
+        // Simply log the limit being configured too low.
+        // If we exceed the limit during the process, we will fail and the user
+        // will have to update the limit and attempt to re-run
+        LOG_DEBUG(<< "Memory limit " << roundMb(memoryLimit) << "MB is configured lower than estimate "
+                  << std::ceil(roundMb(memoryUsage)) << "MB."
+                  << "Analytics process may fail due to low memory limit");
+    }
+    if (m_NumberPartitions > 1) {
         // The maximum number of rows is found by binary search in the interval
         // [numberRows / m_NumberPartitions, numberRows / (m_NumberPartitions - 1)).
 

lib/api/unittest/CDataFrameAnalysisRunnerTest.cc

@@ -95,12 +95,8 @@ BOOST_AUTO_TEST_CASE(testComputeAndSaveExecutionStrategyDiskUsageFlag) {
                         .diskUsageAllowed(false)
                         .outlierSpec();
 
-        // single error is registered that the memory limit is to low
-        LOG_DEBUG(<< "errors = " << core::CContainerPrinter::print(errors));
-        core::CRegex re;
-        re.init("Input error: memory limit.*");
-        BOOST_REQUIRE_EQUAL(1, static_cast<int>(errors.size()));
-        BOOST_TEST_REQUIRE(re.matches(errors[0]));
+        // no error should be registered
+        BOOST_REQUIRE_EQUAL(0, static_cast<int>(errors.size()));
     }
 
     // Test large memory requirement with disk usage