18842: Clean up keep cache set logic a little more

[arvados.git] / sdk / python / arvados / keep.py

diff --git a/sdk/python/arvados/keep.py b/sdk/python/arvados/keep.py
index ce4c6f81f62d997cc5adfd37ebf4e3664ec68be7..8dbad2abb18aeb99a39ab896490751651c45c6b3 100644 (file)
--- a/sdk/python/arvados/keep.py
+++ b/sdk/python/arvados/keep.py
@@ -316,12 +316,10 @@ class KeepBlockCache(object):
                 return n, True
 
     def set(self, slot, blob):
-        tryagain = False
-
         try:
             slot.set(blob)
+            return
         except OSError as e:
-            tryagain = True
             if e.errno == errno.ENOMEM:
                 # Reduce max slots to current - 4, cap cache and retry
                 with self._cache_lock:
@@ -334,13 +332,21 @@ class KeepBlockCache(object):
             elif e.errno == errno.ENODEV:
                 _logger.error("Unable to use disk cache: The underlying filesystem does not support memory mapping.")
         except Exception as e:
-            tryagain = True
+            pass
+        finally:
+            # Check if we should evict things from the cache.  Either
+            # because we added a new thing or there was an error and
+            # we possibly adjusted the limits down, so we might need
+            # to push something out.
+            self.cap_cache()
 
         try:
-            if tryagain:
-                # There was an error.  Evict some slots and try again.
-                self.cap_cache()
-                slot.set(blob)
+            # Only gets here if there was an error the first time. The
+            # exception handler adjusts limits downward in some cases
+            # to free up resources, which would make the operation
+            # succeed.
+            slot.set(blob)
+            self.cap_cache()
         except Exception as e:
             # It failed again.  Give up.
             raise arvados.errors.KeepCacheError("Unable to save block %s to disk cache: %s" % (slot.locator, e))
@@ -349,7 +355,6 @@ class KeepBlockCache(object):
             # slot one way or another.
             slot.ready.set()
 
-        self.cap_cache()
 
 class Counter(object):
     def __init__(self, v=0):