casremote.py: Add workaround for a buildgrid bugtlater/artifactserver-casd

When sending a FetchTreeRequest with two matching digests, the request
will fail. As a workaround for now, we simply ensure that we never do
that (and only request the digest once).

1 files changed, 13 insertions, 0 deletions

diff --git a/src/buildstream/_cas/casremote.py b/src/buildstream/_cas/casremote.py
index 93f4e500c..ea881124e 100644
--- a/src/buildstream/_cas/casremote.py
+++ b/src/buildstream/_cas/casremote.py
@@ -94,6 +94,7 @@ class _CASBatchRead:
         self._requests = []
         self._request = None
         self._sent = False
+        self._digests = None
 
     def add(self, digest):
         assert not self._sent
@@ -103,8 +104,20 @@ class _CASBatchRead:
             self._request.instance_name = self._remote.local_cas_instance_name
             self._requests.append(self._request)
 
+            self._digests = []
+
+        # FIXME: If we accidentally include the same digest in a
+        # request twice, we get an "Unexpected error in RPC handling"
+        # in remote execution with buildgrid (likely casd).
+        #
+        # Not much we can do until that bug is fixed.
+        #
+        if digest in self._digests:
+            return
+
         request_digest = self._request.blob_digests.add()
         request_digest.CopyFrom(digest)
+        self._digests.append(digest)
 
     def send(self, *, missing_blobs=None):
         assert not self._sent