Autogenerate OVN Models

amorenoz commented 3 years ago

This PR aims to provide the following benefits to the ovn probe:

Support the indexing of any table in the OVN NB database
Support any past, present or future version of OVN
Mirror OVN's relationships between tables in skydive's graph

We do so by:

Using the refurnished libovsdb since it provides the following useful features (compared with ebay/go-ovn):
- Unified API (we no longer need a callback per table (e.g: OnLogicalSwitchAdded, OnLogicalRouterAdded...)
- Schema introspection. It supports analyzing the types of each column
- (It also supports a unified CRUD-like API for listing and modifying elements)
- It provides a framework for automatically generating types based on a schema-file
Adding a code generator (called ovnmodelgen)
Autogenerating all the types that describe the OVN Database based on a schema-file.
Autogenerating all the links between tables based on the schema.

As an example, here is the file generated by the metadata generator (ovmetagen) for the table ACL:

//go:generate go run github.com/skydive-project/skydive/graffiti/gendecoder -package github.com/skydive-project/skydive/topology/probes/ovn/ovnmodel
//go:generate go run github.com/mailru/easyjson/easyjson $GOFILE

// Code generated by ovnmetagen
// DO NOT EDIT.

package ovnmodel

import (
    "encoding/json"
    "fmt"

    "github.com/skydive-project/skydive/graffiti/getter"
    "github.com/skydive-project/skydive/graffiti/graph"
)

// ACL defines the type used by both libovsdb and skydive for table ACL
// easyjson:json
// gendecoder
type ACL struct {
    UUID        string            `ovsdb:"_uuid" json:",omitempty" `
    Action      string            `ovsdb:"action" json:",omitempty" `
    Direction   string            `ovsdb:"direction" json:",omitempty" `
    ExternalIDs map[string]string `ovsdb:"external_ids" json:",omitempty" `
    Log         bool              `ovsdb:"log" json:",omitempty" `
    Match       string            `ovsdb:"match" json:",omitempty" `
    Meter       []string          `ovsdb:"meter" json:",omitempty" `
    Name        []string          `ovsdb:"name" json:",omitempty" `
    Priority    int               `ovsdb:"priority" json:",omitempty" `
    Severity    []string          `ovsdb:"severity" json:",omitempty" `

    ExternalIDsMeta graph.Metadata `json:",omitempty" field:"Metadata"`
}

func (t *ACL) Metadata() graph.Metadata {
    // Generate Metadata from maps
    t.ExternalIDsMeta = graph.NormalizeValue(t.ExternalIDs).(map[string]interface{})

    return graph.Metadata{
        "Type":    "ACL",
        "Manager": "ovn",
        "UUID":    t.GetUUID(),
        "Name":    t.GetName(),
        "OVN":     t,
    }
}

func (t *ACL) GetUUID() string {
    return t.UUID
}

func (t *ACL) GetName() string {
    if name := t.UUID; name != "" {
        return name
    }
    return t.GetUUID()
}

// ACLDecoder implements a json message raw decoder
func ACLDecoder(raw json.RawMessage) (getter.Getter, error) {
    var t ACL
    if err := json.Unmarshal(raw, &t); err != nil {
        return nil, fmt.Errorf("unable to unmarshal ACL metadata %s: %s", string(raw), err)
    }
    return &t, nil
}

Most of the struct can be used for both the Metadata and the OVSDB unmarshalling. The only exception is the map[string]string that need to be converted into graph.Metadata fields for things like MetadataIndexers to work.

Also, since the building of the ovn probe has become more complicated, this PR makes ovn probe building conditional, e.g: WITH_OVN=true is required to build OVN support

amorenoz commented 3 years ago

@lebauce I think this is ready for the first round of review, PTAL