Add comments for how after_run() and end() behave if session.run() raises

exception.
Change: 150947137

1 files changed, 19 insertions, 2 deletions

diff --git a/tensorflow/python/training/session_run_hook.py b/tensorflow/python/training/session_run_hook.py
index 13f8ba1b6e..09da63eb68 100644
--- a/tensorflow/python/training/session_run_hook.py
+++ b/tensorflow/python/training/session_run_hook.py
@@ -62,15 +62,24 @@ look at following code:
       sess.run(your_fetches)
 
 Above user code leads to following execution:
-  call hooks.begin
+  call hooks.begin()
   sess = tf.Session()
+  call hooks.after_create_session()
   while not stop is requested:
     call hooks.before_run()
-    results = sess.run(merged_fetches)
+    try:
+      results = sess.run(merged_fetches)
+    except (errors.OutOfRangeError, StopIteration):
+      break
     call hooks.after_run()
   call hooks.end()
   sess.close()
 
+Note that if sess.run() raises OutOfRangeError or StopIteration then
+hooks.after_run() will not be called but hooks.end() will still be called.
+If sess.run() raises any other exception then neither hooks.after_run() nor
+hooks.end() will be called.
+
 @@SessionRunHook
 @@SessionRunArgs
 @@SessionRunContext
@@ -149,6 +158,8 @@ class SessionRunHook(object):
     The `run_context` argument is the same one send to `before_run` call.
     `run_context.request_stop()` can be called to stop the iteration.
 
+    If `session.run()` raises any exceptions then `after_run()` is not called.
+
     Args:
       run_context: A `SessionRunContext` object.
       run_values: A SessionRunValues object.
@@ -161,6 +172,12 @@ class SessionRunHook(object):
     The `session` argument can be used in case the hook wants to run final ops,
     such as saving a last checkpoint.
 
+    If `session.run()` raises exception other than OutOfRangeError or
+    StopIteration then `end()` is not called.
+    Note the difference between `end()` and `after_run()` behavior when
+    `session.run()` raises OutOfRangeError or StopIteration. In that case
+    `end()` is called but `after_run()` is not called.
+
     Args:
       session: A TensorFlow Session that will be soon closed.
     """