Compress similarity model (#986)

Fixes #939

bugbug/similarity.py

@@ -177,7 +177,9 @@ class BaseSimilarity(abc.ABC):
         return
 
     def save(self):
-        joblib.dump(self, f"{self.__class__.__name__.lower()}.similaritymodel")
+        path = f"{self.__class__.__name__.lower()}.similaritymodel"
+        joblib.dump(self, path)
+        return path
 
     @staticmethod
     def load(model_file_name):

scripts/similarity_trainer.py

@@ -5,12 +5,14 @@
 # You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import argparse
+import os
 import sys
 from logging import INFO, basicConfig, getLogger
 
 from sklearn.feature_extraction.text import TfidfVectorizer
 
 from bugbug import bugzilla, db, similarity
+from bugbug.utils import zstd_compress
 
 basicConfig(level=INFO)
 logger = getLogger(__name__)
@@ -58,7 +60,9 @@ def main():
             cleanup_urls=args.cleanup_urls, nltk_tokenizer=args.nltk_tokenizer
         )
 
-    model.save()
+    path = model.save()
+    assert os.path.exists(path)
+    zstd_compress(path)
 
 
 if __name__ == "__main__":