malo-denielou opened a new pull request, #40880:
URL: https://github.com/apache/beam/pull/40880
When runners require deterministic pipeline graphs across restarts (such as
for pipeline graph equality checks on controller failover), two map-iteration
paths in the Go SDK can produce non-deterministic ordering:
1. In `pipelinex.computeRoots`, root transform IDs are collected by ranging
over `xforms` (`map[string]*pipepb.PTransform`) and passed directly to
`TopologicalSort(xforms, roots)`. While `TopologicalSort` already sorts its
internal frontier (`ret.next`) and output keys for determinism, the initial
`roots` slice was left in random map iteration order. Sorting `roots` with
`sort.Sort(idSorted(roots))` makes the root topological order deterministic.
2. In `xlangx.HandlerParams.Inputs()` and `Outputs()`, `PCol` entries are
collected by ranging over `InputsMap` and `OutputsMap` (`map[string]int`) in
random order, which can cause expansion handlers to register cross-language
inputs or outputs in varying orders across runs. Sorting the returned slice by
`PCol.Index` (with `PCol.Local` as a tie-breaker) ensures a consistent order
while still supporting sparse index maps (such as when `xlang.SetOutputCoder`
rewrites `OutputsMap` to a single entry at an index greater than 0).
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