I've been able to reproduce this on 8.3 without XO involved (just by querying the /host_logs_download endpoint).
The only error I can see in xensource.log is at the end of a successful download call:
xapi: [debug||6246 HTTPS 10.1.0.100->:::80|get_host_logs_download|xapi_http] Leaving RBAC-handler in xapi_http after: HANDLE_INVALID: [ task; OpaqueRef:b40bd070-307e-f05d-91b5-562dc2f71e6d ]
xapi: [error||6246 :::80||backtrace] get_host_logs_download failed with exception Db_exn.DBCache_NotFound("missing row", "task", "OpaqueRef:b40bd070-307e-f05d-91b5-562dc2f71e6d")
xapi: [error||6246 :::80||backtrace] Raised Db_exn.DBCache_NotFound("missing row", "task", "OpaqueRef:b40bd070-307e-f05d-91b5-562dc2f71e6d")
xapi: [error||6246 :::80||backtrace] 1/19 xapi Raised at file ocaml/database/db_rpc_client_v1.ml, line 33
xapi: [error||6246 :::80||backtrace] 2/19 xapi Called from file ocaml/xapi/db_actions.ml, line 2577
xapi: [error||6246 :::80||backtrace] 3/19 xapi Called from file ocaml/xapi/taskHelper.ml, line 272
xapi: [error||6246 :::80||backtrace] 4/19 xapi Called from file ocaml/xapi/context.ml, line 515
xapi: [error||6246 :::80||backtrace] 5/19 xapi Called from file ocaml/xapi/context.ml, line 522
xapi: [error||6246 :::80||backtrace] 6/19 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6246 :::80||backtrace] 7/19 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6246 :::80||backtrace] 8/19 xapi Called from file ocaml/xapi/xapi_http.ml, line 108
xapi: [error||6246 :::80||backtrace] 9/19 xapi Called from file ocaml/xapi/server_helpers.ml, line 69
xapi: [error||6246 :::80||backtrace] 10/19 xapi Called from file ocaml/xapi/server_helpers.ml, line 96
xapi: [error||6246 :::80||backtrace] 11/19 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6246 :::80||backtrace] 12/19 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6246 :::80||backtrace] 13/19 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6246 :::80||backtrace] 14/19 xapi Called from file ocaml/libs/log/debug.ml, line 267
xapi: [error||6246 :::80||backtrace] 15/19 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6246 :::80||backtrace] 16/19 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6246 :::80||backtrace] 17/19 xapi Called from file ocaml/xapi/xapi_http.ml, line 364
xapi: [error||6246 :::80||backtrace] 18/19 xapi Called from file ocaml/xapi/xapi_http.ml, line 370
xapi: [error||6246 :::80||backtrace] 19/19 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6246 :::80||backtrace]
xapi: [error||6246 :::80||http_internal_errors] Responding with 500 Internal Error due to Db_exn.DBCache_NotFound("missing row", "task", "OpaqueRef:b40bd070-307e-f05d-91b5-562dc2f71e6d")
xapi: [debug||6246 :::80||http_internal_errors] Raised at Debug.with_thread_associated in file \\"ocaml/libs/log/debug.ml\\", line 267, characters 6-15\\nCalled from Http_svr.handle_one in file \\"ocaml/libs/http-lib/http_svr.ml\\", line 509, characters 4-32\\nCalled from Http_svr.let@ in file \\"ocaml/libs/http-lib/http_svr.ml\\" (inlined), line 46, characters 19-22\\nCalled from Http_svr.handle_one in file \\"ocaml/libs/http-lib/http_svr.ml\\", line 508, characters 4-195\\n
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace] 4/6 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, lineApr 3 15:09:04 xcp-gtn-ip12 xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace] 4/6 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace] 5/6 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace] 6/6 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace]
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] handler:http/get_host_logs_download D:4e4d887163d8 failed with exception Forkhelpers.Subprocess_failed(1)
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] Raised Forkhelpers.Subprocess_failed(1)
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 1/13 xapi Raised at file ocaml/libs/log/debug.ml, line 267
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 2/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 3/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 4/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 5/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 6/13 xapi Called from file ocaml/xapi/xapi_http.ml, line 257
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 7/13 xapi Called from file ocaml/xapi/rbac.ml, line 188
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 8/13 xapi Called from file ocaml/xapi/rbac.ml, line 197
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 9/13 xapi Called from file ocaml/xapi/server_helpers.ml, line 69
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 10/13 xapi Called from file ocaml/xapi/server_helpers.ml, line 96
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 11/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 12/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 13/13 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace] 4/6 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace] 5/6 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace] 6/6 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6372 :::80|handler:http/get_host_logs_download D:4e4d887163d8|backtrace]
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] handler:http/get_host_logs_download D:4e4d887163d8 failed with exception Forkhelpers.Subprocess_failed(1)
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] Raised Forkhelpers.Subprocess_failed(1)
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 1/13 xapi Raised at file ocaml/libs/log/debug.ml, line 267
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 2/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 3/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 4/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 5/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 6/13 xapi Called from file ocaml/xapi/xapi_http.ml, line 257
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 7/13 xapi Called from file ocaml/xapi/rbac.ml, line 188
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 8/13 xapi Called from file ocaml/xapi/rbac.ml, line 197
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 9/13 xapi Called from file ocaml/xapi/server_helpers.ml, line 69
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 10/13 xapi Called from file ocaml/xapi/server_helpers.ml, line 96
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 11/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 12/13 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace] 13/13 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6372 :::80|xapi_http_session_check D:7cc5eb59b433|backtrace]
xapi: [ info||6372 :::80|xapi_http_session_check D:7cc5eb59b433|taskhelper] task Xapi#getResource /host_logs_download R:83146129fe1c forwarded
xapi: [debug||6372 :::80|xapi_http_session_check D:7cc5eb59b433|taskhelper] the status of R:83146129fe1c is failure; cannot set it to `failure
xapi: [debug||6372 HTTPS 10.1.0.100->:::80|get_host_logs_download|xapi_http] Leaving RBAC-handler in xapi_http after: INTERNAL_ERROR: [ Subprocess exited with unexpected code 1 ]
xapi: [error||6372 :::80||backtrace] get_host_logs_download failed with exception Forkhelpers.Subprocess_failed(1)
xapi: [error||6372 :::80||backtrace] Raised Forkhelpers.Subprocess_failed(1)
xapi: [error||6372 :::80||backtrace] 1/14 xapi Raised at file ocaml/libs/log/debug.ml, line 267
xapi: [error||6372 :::80||backtrace] 2/14 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80||backtrace] 3/14 xapi Called from file ocaml/xapi/xapi_http.ml, line 114
xapi: [error||6372 :::80||backtrace] 4/14 xapi Called from file ocaml/xapi/server_helpers.ml, line 69
xapi: [error||6372 :::80||backtrace] 5/14 xapi Called from file ocaml/xapi/server_helpers.ml, line 96
xapi: [error||6372 :::80||backtrace] 6/14 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80||backtrace] 7/14 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80||backtrace] 8/14 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6372 :::80||backtrace] 9/14 xapi Called from file ocaml/libs/log/debug.ml, line 267
xapi: [error||6372 :::80||backtrace] 10/14 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 24
xapi: [error||6372 :::80||backtrace] 11/14 xapi Called from file ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml, line 39
xapi: [error||6372 :::80||backtrace] 12/14 xapi Called from file ocaml/xapi/xapi_http.ml, line 364
xapi: [error||6372 :::80||backtrace] 13/14 xapi Called from file ocaml/xapi/xapi_http.ml, line 370
xapi: [error||6372 :::80||backtrace] 14/14 xapi Called from file ocaml/libs/log/debug.ml, line 250
xapi: [error||6372 :::80||backtrace]
xapi: [error||6372 :::80||http_internal_errors] Responding with 500 Internal Error due to Forkhelpers.Subprocess_failed(1)
xapi: [debug||6372 :::80||http_internal_errors] Raised at Debug.with_thread_associated in file \\"ocaml/libs/log/debug.ml\\", line 267, characters 6-15\\nCalled from Http_svr.handle_one in file \\"ocaml/libs/http-lib/http_svr.ml\\", line 509, characters 4-32\\nCalled from Http_svr.let@ in file \\"ocaml/libs/http-lib/http_svr.ml\\" (inlined), line 46, characters 19-22\\nCalled from Http_svr.handle_one in file \\"ocaml/libs/http-lib/http_svr.ml\\", line 508, characters 4-195\\n
And then the subsequent download stalls without any indication. I will investigate this further but just to confirm, can any of you see these or similar errors in your logs? Do you have occasional successful downloads followed by failures?