{"record":{"id":"ec4411052d1a3027","repo":"hashicorp/nomad","slug":"unexpected-nil-volume-returned-for-id-v","errorCode":null,"errorMessage":"Unexpected nil volume returned for ID: %v","messagePattern":"Unexpected nil volume returned for ID: (.+?)","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"client/allocrunner/csi_hook.go","lineNumber":329,"sourceCode":"\t\t\tAllocationID:   c.alloc.ID,\n\t\t\tNodeID:         c.alloc.NodeID,\n\t\t\tExternalNodeID: result.stub.ExternalNodeID,\n\t\t\tClaim:          claimType,\n\t\t\tAccessMode:     request.AccessMode,\n\t\t\tAttachmentMode: request.AttachmentMode,\n\t\t\tWriteRequest: structs.WriteRequest{\n\t\t\t\tRegion:    c.alloc.Job.Region,\n\t\t\t\tNamespace: c.alloc.Job.Namespace,\n\t\t\t\tAuthToken: c.nodeSecret,\n\t\t\t},\n\t\t}\n\n\t\tresp, err := c.claimWithRetry(req)\n\t\tif err != nil {\n\t\t\treturn fmt.Errorf(\"could not claim volume %s: %w\", req.VolumeID, err)\n\t\t}\n\t\tif resp.Volume == nil {\n\t\t\treturn fmt.Errorf(\"Unexpected nil volume returned for ID: %v\", request.Source)\n\t\t}\n\n\t\tresult.volume = resp.Volume\n\n\t\t// populate data we'll write later to disk\n\t\tresult.stub.VolumeID = resp.Volume.ID\n\t\tresult.stub.VolumeNamespace = resp.Volume.Namespace\n\t\tresult.stub.VolumeExternalID = resp.Volume.RemoteID()\n\t\tresult.stub.PluginID = resp.Volume.PluginID\n\t\tresult.publishContext = resp.PublishContext\n\t}\n\n\treturn nil\n}\n\nfunc (c *csiHook) mountVolumes(results map[string]*volumePublishResult) error {\n\n\tfor _, result := range results {","sourceCodeStart":311,"sourceCodeEnd":347,"githubUrl":"https://github.com/hashicorp/nomad/blob/482b49bf1aec006f089bcfc7e632d8f6ac303e5e/client/allocrunner/csi_hook.go#L311-L347","documentation":"After a successful claim RPC, the hook expects the server response to carry the claimed CSIVolume. If the server returns success but resp.Volume is nil, the client treats this as an unexpected/invalid server response and fails the claim. It is a defensive check against a server/client version mismatch or inconsistent server state.","triggerScenarios":"claimWithRetry returns a nil-error response whose Volume field is nil — a malformed or unexpected server reply for the volume identified by request.Source (the volume's source name in the jobspec).","commonSituations":"Running a newer client against an older Nomad server (or vice versa) where the claim handler doesn't populate the volume in the response; corrupted server state store for the volume; custom patches/proxies altering the RPC response.","solutions":["Check Nomad client/server version compatibility — upgrade the server if the client expects the volume to be returned in the claim response.","Inspect server logs for the volume-claim RPC to find why the response omitted the volume.","Verify volume integrity: `nomad volume status <volume_id>`; re-register the volume if server state is inconsistent.","File a bug with Nomad if the server consistently returns a nil volume on a successful claim."],"exampleFix":null,"handlingStrategy":"type-guard","validationCode":"// after claim RPC, guard the response before using it\nif resp == nil || resp.Volume == nil {\n    return fmt.Errorf(\"server returned no volume for claim\")\n}","typeGuard":"func hasVolume(resp *structs.CSIVolumeClaimResponse) bool {\n    return resp != nil && resp.Volume != nil && resp.Volume.ID != \"\"\n}","tryCatchPattern":"if err == nil && resp.Volume == nil {\n    // treat as server/client version mismatch: log and retry or upgrade server\n}","preventionTips":["Keep Nomad client and server versions aligned (upgrade servers first).","Watch for nil responses in custom RPC handlers/proxies.","Report persistent nil-volume responses to the Nomad maintainers.","Validate volume state in the server state store after unexpected responses."],"tags":["nomad","csi","rpc","nil-response"],"backgroundTag":"csi-volume-claim-failed","analyzedSha":"482b49bf1aec006f089bcfc7e632d8f6ac303e5e","analyzedAt":"2026-09-04T07:54:14.808Z","contentChangedAt":"2026-09-04T07:54:14.808Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}