Add bounded concurrent writes to import

[Mike Krüger (mkrueger)]

Summary

Import currently awaits every document write sequentially, making large imports sensitive to per-request network latency. Stream input while keeping a bounded set of writes in flight instead.

• Default to 16 concurrent writes; add --concurrency / MCP concurrency, requiring a positive integer. Use --concurrency=1 for sequential, file-order behavior.
• Refill a slot as soon as any write completes rather than waiting for earlier writes. Keep buffering bounded and disable unused write response bodies.
• Serialize result accounting and diagnostics. Stop scheduling on the first observed write failure unless --continue-on-error is set; drain and account for already-started writes.
• Drain started writes before returning on parsing errors, unexpected failures, or cancellation. Pass cancellation through input and SDK writes and never report success after cancellation.
• Preserve dry runs, insert/upsert status handling, request charges, and structured result shape.
• Update CLI help, examples, localization catalog, README, command/MCP docs, and changelog.

Behavior notes

Concurrent writes can complete out of order and may succeed after another write fails. Imports remain non-transactional. Use concurrency 1 for repeated-ID ordering or exact sequential stop-on-error behavior. SDK retry behavior and client configuration are unchanged; this does not increase provisioned RU/s.

Independent branch based on main.

[Copilot]

🟡 Changes recommended

The MCP schema permits non-positive concurrency values despite the positive-integer contract.

1 open finding

• Add minimum: 1 constraint to concurrency MCP schema · New

What changed in this PR

Adds bounded concurrency to imports to improve throughput while preserving streaming, cancellation, and result accounting.

Changes:

• Adds configurable concurrent writes, defaulting to 16.
• Drains in-flight writes on failures and cancellation.
• Updates tests, help, localization, and documentation.

File	Description
README.md	Documents concurrent imports.
CHANGELOG.md	Records the improvement.
docs/​commands.md	Documents import behavior and options.
docs/​mcp.md	Documents MCP concurrency.
CosmosDBShell/​lang/​en.ftl	Adds localized help text.
l10n/​CosmosDBShell.json	Regenerates the localization catalog.
ImportCommand.cs	Implements bounded concurrent writes.
ImportConcurrencyTests.cs	Tests concurrency, failures, and cancellation.
ToolOperationsTests.cs	Tests MCP option metadata.

🧠 Review effort: Balanced

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[github-code-quality]

Code Coverage Overview

Languages: C#

C# / code-coverage/dotnet

The overall line coverage in commit 18cd3d9 in the dev/mkrueger/concurr... branch is 67%. The line coverage in commit 3a8eb87 in the main branch is 66%.

Show a line coverage summary of the most impacted files.

File	main 3a8eb87	dev/mkrueger/concurr... 18cd3d9	+/-
D:\a\CosmosDBSh...olOperations.cs	95%	95%	0%
D:\a\CosmosDBSh...andException.cs	91%	91%	0%
D:\a\CosmosDBSh...ionAttribute.cs	100%	100%	0%
D:\a\CosmosDBSh...mands\Option.cs	42%	44%	+2%
D:\a\CosmosDBSh...mportCommand.cs	50%	83%	+33%

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_{Updated October 08, 2026 09:48 UTC}

[Copilot]

🟢 Approval recommended

The bounded scheduling implementation is well tested and its schema, localization, and documentation changes are consistent.

0 open findings

1 resolved since last review

• Add minimum: 1 constraint to concurrency MCP schema

🧠 Review effort: Balanced

---

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[Copilot]

🟢 Approval recommended

The implementation is bounded, well-documented, and comprehensively covers concurrency and failure behavior with focused tests.

0 open findings

🧠 Review effort: Balanced

---

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