Use alternate executor id for push stage when sharing sequenced task executor

with invert stage.

2 files changed, 18 insertions, 0 deletions

diff --git a/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.cpp b/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.cpp
index 41653889b8f..c54f182891c 100644
--- a/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.cpp
+++ b/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.cpp
@@ -18,4 +18,13 @@ ISequencedTaskExecutor::getExecutorIdFromName(vespalib::stringref componentId) c
     return getExecutorId(hashfun(componentId));
 }
 
+ISequencedTaskExecutor::ExecutorId
+ISequencedTaskExecutor::get_alternate_executor_id(ExecutorId id, uint32_t bias) const
+{
+    if ((bias % _numExecutors) == 0) {
+        bias = 1;
+    }
+    return ExecutorId((id.getId() + bias) % _numExecutors);
+}
+
 }
diff --git a/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.h b/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.h
index 06cc37616c0..0e931838279 100644
--- a/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.h
+++ b/staging_vespalib/src/vespa/vespalib/util/isequencedtaskexecutor.h
@@ -43,6 +43,15 @@ public:
     ExecutorId getExecutorIdFromName(vespalib::stringref componentId) const;
 
     /**
+     * Returns an executor id that is NOT equal to the given executor id,
+     * using the given bias to offset the new id.
+     *
+     * This is relevant for pipelining operations on the same component,
+     * by doing pipeline steps in different executors.
+     */
+    ExecutorId get_alternate_executor_id(ExecutorId id, uint32_t bias) const;
+
+    /**
      * Schedule a task to run after all previously scheduled tasks with
      * same id.
      *