[ML] Adds an mml check to trigger an error when mml value is invalid. (#18678) (#18711)

This adds an additional check and corresponding error message to the validation of the model memory limit. If the parsing of the memory model limit results in 0 bytes the message will be triggered. This behaviour catches both correctly formatted but invalid strings (like 0mb) and invalid strings (like asdf).

x-pack/plugins/ml/server/models/job_validation/__tests__/validate_model_memory_limit.js

@@ -192,4 +192,32 @@ describe('ML - validateModelMemoryLimit', () => {
     );
   });
 
+  it('Called with specified invalid mml of "0mb"', () => {
+    const dtrs = createDetectors(1);
+    const job = getJobConfig(['instance'], dtrs);
+    const duration = { start: 0, end: 1 };
+    job.analysis_limits.model_memory_limit = '0mb';
+
+    return validateModelMemoryLimit(callWithRequest, job, duration).then(
+      (messages) => {
+        const ids = messages.map(m => m.id);
+        expect(ids).to.eql(['mml_value_invalid']);
+      }
+    );
+  });
+
+  it('Called with specified invalid mml of "asdf"', () => {
+    const dtrs = createDetectors(1);
+    const job = getJobConfig(['instance'], dtrs);
+    const duration = { start: 0, end: 1 };
+    job.analysis_limits.model_memory_limit = 'asdf';
+
+    return validateModelMemoryLimit(callWithRequest, job, duration).then(
+      (messages) => {
+        const ids = messages.map(m => m.id);
+        expect(ids).to.eql(['mml_value_invalid']);
+      }
+    );
+  });
+
 });

x-pack/plugins/ml/server/models/job_validation/messages.json

@@ -151,6 +151,10 @@
     "status": "ERROR",
     "text": "The model memory limit is greater than the max model memory limit configured for this cluster."
   },
+  "mml_value_invalid": {
+    "status": "ERROR",
+    "text": "{{mml}} is not a valid value for model memory limit. The value should be specified in bytes e.g. 10MB"
+  },
   "estimated_mml_greater_than_mml": {
     "status": "INFO",
     "text": "The estimated model memory limit is greater than the model memory limit you have configured."

x-pack/plugins/ml/server/models/job_validation/validate_model_memory_limit.js

@@ -96,7 +96,12 @@ export async function validateModelMemoryLimit(callWithRequest, job, duration) {
     // the max mml
     if (runEstimateGreaterThenMml && mml !== null) {
       const mmlBytes = numeral(mml).value();
-      if (mmlEstimateBytes > mmlBytes) {
+      if (mmlBytes === 0) {
+        messages.push({
+          id: 'mml_value_invalid',
+          mml
+        });
+      } else if (mmlEstimateBytes > mmlBytes) {
         messages.push({
           id: 'estimated_mml_greater_than_mml',
           maxModelMemoryLimit,