Adding devel.

---------- Forwarded message ---------
From: Nir Soffer <nsoffer@redhat.com>
Date: Wed, 10 Oct 2018, 11:07
Subject: Re: VDSM API schema inconsistencies
To: Piotr Kliczewski <pkliczew@redhat.com>
Cc: Dan Kenigsberg <danken@redhat.com>, Edward Haas <ehaas@redhat.com>, Milan Zamazal <mzamazal@redhat.com>, Tomasz Baranski <tbaransk@redhat.com>, Francesco Romani <fromani@redhat.com>, Irit Goihman <igoihman@redhat.com>, Marcin Sobczyk <msobczyk@redhat.com>

On Wed, 10 Oct 2018, 10:21 Piotr Kliczewski, <pkliczew@redhat.com> wrote:

+Nir

On Wed, Oct 10, 2018 at 8:39 AM Marcin Sobczyk <msobczyk@redhat.com> wrote:

Hi,

I would love to get some feedback from you about it on the VDSM call today so if you have a moment, please take a look.

Marcin

---------- Forwarded message ---------
From: Marcin Sobczyk <msobczyk@redhat.com>
Date: Mon, Oct 8, 2018 at 2:40 PM
Subject: VDSM API schema inconsistencies
To: devel <devel@ovirt.org>

Hi,

when I was working on BZ#1624306 it turned out, that even if I'd fix the help-printing code in vdsm-client, there's still a lot of inconsistencies in API's schema files.

After some investigation, I found that there's a code for reporting schema inconsistencies, but it's turned off because it bloats the logs.

Right, an it should remain like this. In runtime

we never want these warnings.

There's also a "strict" mode that raises an exception each time an inconsistency is found, but it's also off because there's so many of them.

Same.

Both are debugging aids for developers, to

make it easy to check the schema.

I think that no one wants to maintain both: the actual code and schema files.

This is not a big issue. We rarely add or

change APIs. But it is nice if we don't need to

manualy make the schema correct.

My idea would be to make the schema derived from the code at build time as a long-term effort.

This cannot work, since clients depend on the schema, it should not change if when someone

makes uintended change in the code.

It should work in the opposite way, you change the schema, and generate new code frome schema.

Threre are existing tools like grpc and thrift that

work in this way. For long term we should drop

our jsonrpc/stomp stack and move to grpc.

For short term we can just fix the schema to

reflect actual engine interaction. when engine

and schema do not match, engine is usualy

right. For responses, if engine can handle the

response the code is right.

Please do not make RPC code more complex

and inefficient for improving schema issues

detection. I would rather remove this code

instead.

Before we can do that though, we need to address the inconsistencies first.

https://gerrit.ovirt.org/#/q/status:open+project:vdsm+branch:master+topic:vdsm-api-schema-debug

This is a series of patches that helps fixing schema issues. What it does, is it adds a bunch of information from stack to vastly ease the process of fixing them. The logging level is also changed from 'WARNING' to 'DEBUG'. Here's an example of a logged entry:

Host.setKsmTune
With message: Required property pages_to_scan is not provided when calling Host.setKsmTune
With backtrace: [
        [
                "_verify_object_type",
                {
                        "call_arg_keys":[
                                "merge_across_nodes",
                                "run"
                        ],
                        "schema_type_name":"KsmTuneParams"
                }
        ],
        [
                "_verify_complex_type",
                {
                        "schema_type_type":"object"
                }
        ]
]

To make it work, a patch for OST's 'basic-master-suite' is on the way that switches 'schema.inconsistency' logger's logging level do 'DEBUG'. That way, we can find all reported errors in 'vdsm-schema-error.log' files.

An initial report that groups reported errors by namespaces/methods has also been made. Please note, that an implementation that completely avoids error duplicates is really hard and IMHO not worth the effort. You can find the results here:

Host: https://pastebin.com/YM2XnvTV

Image: https://pastebin.com/GRc1yErL

LVMVolumeGroup: https://pastebin.com/R1276gTu

SDM: https://pastebin.com/P3tfYEDD

StorageDomain: https://pastebin.com/Q0DxKgF5

StoragePool: https://pastebin.com/VXFWpfRC

VM: https://pastebin.com/tDC60c29

Volume: https://pastebin.com/TYkr9Zsd

|jobs|: https://pastebin.com/jeXpYyz9

|virt|: https://pastebin.com/nRREuEub

File a bug per vertical (infra, storage, virt) for

these issues. Since we don't know about real user issues with these apis this must be incorrect schema.