OSS Multipart Upload Diagnosis

Diagnose Alibaba Cloud OSS large-file upload problems: "my 40GB backup multipart upload is stuck at 0%", "the upload was interrupted halfway, how do I resume it", "uploading a large file keeps failing", "the bucket seems empty but storage capacity is occupied by multipart fragments".

Core approach: verify the caller identity, locate the bucket's real region with the read-only GetBucketInfo control-plane query (ListBuckets fallback), enumerate unfinished multipart upload events with the read-only ListMultipartUploads to identify fragments, check the user's part size / concurrency against the official OSS multipart limits, and attribute stuck / interrupted / failed uploads to a server-side, client-side, or network cause via a decision tree. Conclude with evidence-based findings only; this skill never changes anything.

Absolute Rules

1. ABSOLUTE PROHIBITION (read-only enforcement): Under NO circumstances may you generate, write, or execute any command/script calling a mutating OSS API — including AbortMultipartUpload (fragment cleanup), PutObject, UploadPart, CompleteMultipartUpload, DeleteObject, DeleteBucket, or any ACL/policy/lifecycle configuration change. Fragment cleanup is a WRITE operation: this skill only outputs manual cleanup guidance and command templates for the user to execute themselves (see references/fragment-cleanup-guide.md).
2. MANDATORY entry-point enforcement: All OSS diagnostics MUST be performed by running the scripts under scripts/ (multipart_upload_diagnosis.py as the entry, sts_token.py for identity). The Agent is forbidden from assembling its own ossutil / SDK / curl commands against the OSS control plane or bypassing the scripts — the scripts embed timeout, error degradation, and observability guarantees that ad-hoc commands lack. Read the script output, interpret it, and compose the report; do not re-implement the queries.
3. ABSOLUTE PROHIBITION (credential handling): Never read, print, or pass AK/SK/STS tokens explicitly. The OSS SDK resolves credentials exclusively through the Alibaba Cloud default credential chain library; the identity check uses the aliyun CLI default credential chain. Never accept AK/SK from the user or from another script.
4. NO FABRICATION: Every conclusion must be grounded in data actually returned by GetBucketInfo / ListBuckets / ListMultipartUploads / GetCallerIdentity or the user-provided parameters. If a query fails or returns empty, record it and state the limitation — never invent upload IDs, fragment counts, or speed figures.
5. EXECUTION RULE FOR ERRORS: On any API error, log [WARN] <category>: <message> to stderr, continue with the remaining steps (including the ListBuckets fallback), and still produce the final report with STATUS: DEGRADED and a NEXT_ACTION line — never silently skip or abort without a report.
6. SCOPE BOUNDARY: This skill only answers multipart / resumable upload questions (stuck / interrupted / failed attribution, part parameter sanity, fragment identification and cost impact, resume guidance). It does NOT handle single-request upload error-code semantics (EntityTooLarge / SignatureDoesNotMatch / FileAlreadyExists — defer to alibabacloud-oss-transfer-error-code-diagnosis), download problems, billing deduction details, or executing any cleanup — for such requests, state the boundary and give manual guidance only.

Official Doc Verification