Notes for Developers¶
Upgrading the gRPC protobuf files¶
Buildgrid’s gRPC stubs are not built as part of installation. Instead, they are precompiled and shipped with the source code. The protobufs are prone to compatibility-breaking changes, so we update them manually.
First bring the updated proto file into the source tree. For example, if updating
the remote execution proto, replace the old
with the newer one.
Then, compile the protobufs. Continuing with the
pip install grpcio grpcio-tools grpc-stubs mypy-protobuf python -m grpc_tools.protoc -Ibuildgrid/_protos/ --python_out=buildgrid/_protos --grpc_python_out=buildgrid/_protos --mypy_out=buildgrid/_protos build/bazel/remote/execution/v2/remote_execution.proto
The most important thing here is to make sure that
buildgrid/_protos is in your include path with
If all goes well, the new files should have been generated.
Implementing a data store for the Scheduler¶
buildgrid.server.scheduler.Scheduler can be configured to use one of
multiple backends. Currently in-memory and SQL-based backends are available and
It is possible to implement a new backend, by implementing the data store interface
buildgrid.server.persistence.interface.DataStoreInterface) and adding
a class to
buildgrid/_app/settings/parser.py to allow the interface to be
The implementation is free to decide how to persist the data, as long as all of
the abstract methods of
DataStoreInterface are implemented. The implementations
are only required to exist as specified; the details are left up to the author.
This allows implementations to make unneccessary methods do nothing for example,
as long as the expected data type is returned. There may be nothing to do for
enabling/disabling monitoring for some implementations for example.
Backend implementations are also required to implement some way of triggering
the events that are used when streaming updates to clients. These are instances
notify_change should be used to
indicate an update message should be sent, and
notify_stop should be used to
indicate that the thread handling the stream should check whether the client
is connected, and stop if not. Implementations should only really need to use
notify_change, as the disconnect logic is in the
Both existing implementations start a thread which periodically checks the
state of the data for jobs that are being watched and compares it with the
previous state. If it detects a change, then it calls
the relevant event, which is stored in the
buildgrid.utils.JobWatchSpec for the affected job, which is in
self.watched_jobs dictionary. Adding/removing entries from
this dictionary is handled by the
DataStoreInterface class, so doesn’t
need to be a concern for implementations.
The class to parse a YAML tag to allow the data store implementation to be
configured should inherit from
YamlFactory and have a
which returns an instance of the implementation. There are no other limitations
on what it should and shouldn’t do. In order to allow the parser to understand
the tag, the
get_parser function at the bottom of
parser.py should also
be modified to add a constructor for the new tag.