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Diffstat (limited to 'docs/programming-guide.md')
| -rw-r--r-- | docs/programming-guide.md | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/docs/programming-guide.md b/docs/programming-guide.md index 49f319ba77..c60de6e970 100644 --- a/docs/programming-guide.md +++ b/docs/programming-guide.md @@ -1306,6 +1306,12 @@ vecAccum = sc.accumulator(Vector(...), VectorAccumulatorParam()) </div> +For accumulator updates performed inside <b>actions only</b>, Spark guarantees that each task's update to the accumulator +will only be applied once, i.e. restarted tasks will not update the value. In transformations, users should be aware +of that each task's update may be applied more than once if tasks or job stages are re-executed. + + + # Deploying to a Cluster The [application submission guide](submitting-applications.html) describes how to submit applications to a cluster. |