docs(arrow/ipc): document that Writer and FileWriter are not concurrency safe#856
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…ncy safe The IPC Writer and FileWriter wrap an arbitrary io.Writer and write to it without synchronization, so concurrent Write/Close calls can interleave output and corrupt the stream (for example emitting the schema header more than once). Document on both types that they are not safe for concurrent use and that callers must serialize writes themselves, e.g. by funneling records through a channel to a single owning goroutine. Closes apache#55
lidavidm
approved these changes
Jun 18, 2026
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Rationale for this change
Closes #55.
arrow/ipc.Writerandarrow/ipc.FileWriterwrap an arbitraryio.Writerand write to it without any internal synchronization. CallingWrite(orClose) concurrently from multiple goroutines therefore races on both the underlying sink and the writer's own state, which can interleave output and corrupt the IPC stream — for example writing the schema header more than once, as reported in #55.Because an arbitrary
io.Writercannot be assumed to be safe for concurrent use, the writer cannot make this safe on the caller's behalf. The expectation that callers serialize writes was simply undocumented.What changes are included in this PR?
Documentation only. The type doc comments on
WriterandFileWriternow state that they are not safe for concurrent use, explain why (interleaved/duplicated output via an unsynchronizedio.Writer), and direct callers that produce records from multiple goroutines to serialize writes themselves — for example by funneling records through a channel to a single goroutine that owns the writer.No code or behavior changes.
Are these changes tested?
No tests are needed — this is a documentation-only change.
gofmt,go build, andgo vetare clean forarrow/ipc.Are there any user-facing changes?
No API or behavior changes; only added godoc on
ipc.Writerandipc.FileWriter.