Redfish EventService Implementation
rajeswaran.thillaigovindan at gmail.com
Tue May 5 21:43:01 AEST 2020
Further to my previous mail, I wanted to see how a JSON dictionary would
look like for implementing Redfish EventService based on D-Bus match.
The D-Bus match approach is good for implementing life cycle
events((ResourceAdded, ResourceRemoved, ResourceUpdated). In bmcweb, a
Redfish Resource is viewed as having a set of properties which comes
from one or more D-Bus objects. So, when a client subscribes for a
ResourceType, using a JSON dictionary, find the D-Bus object(s) mapped
to the ResourceType and create matches. When the D-Bus match occurs,
again using aJSON dictionary, find the Redfish ResourceType mapped to
the D-Bus object and create events. The JSON dictionary should also
provide the Redifsh URI which needs to be specified in the event. An
example JSON dictionary for mapping the Redifsh ResourceTypes LogEntry
and ComputerSystem is available here :
case of LogEntry, there is one to one mapping of ResourceType to D-Bus
object. In case of ComputerSystem, the properties comes from multiple
D-Bus objects. Do you see any drawback with this approach? Kindly let
me know what you think. Thanks in advance.
On 25-02-2020 19:36, Puli, Apparao wrote:
> Hi Ratan,
> Comments in-line
> On 2/24/2020 12:07 PM, Ratan Gupta wrote:
>> Hi Apparao,
>> On 2/20/20 12:49 AM, Puli, Apparao wrote:
>>> I am sorry for late response as this mail is buried under and got
>>> struck back of my mind.
>>> As i did mentioned in EventService design document, EventLog Monitor
>>> service is not common across the organizations( Example: Intel uses
>>> the redfish event logs file and inotify mechanism for monitoring the
>>> event logs. Where as IBM uses d-bus event log mechanism and they can
>>> relay on match rules). That said challenges with ResourceType
>>> mapping will be different in both monitoring mechanisms. This is
>>> good point. Initially when i started EventService design, i thought
>>> we can have mapping in bmcweb for ResourceTypes with set of
>>> MessageID's for Logged events ( As per Intel design) but not sure
>>> that may become difficult when we expand supported ResourceTypes.
>> If I am getting correctly, Here is the flow which Intel uses.
>> 1. Individual repo have to push the logs using sd_journal_send which
>> will write to the file(/var/log/redfish) by using rsyslog daemon
>> sd_journal_send("MESSAGE=%s","journal text","PRIORITY=%i", <LOG_LEVEL>,
>> * How you would populate the "OriginOfCondition" during sending
>> of event? (https://redfish.dmtf.org/schemas/v1/Event.v1_4_1.json)
> Currently in logServices( logEntry), we are not reporting the
> "OriginOfCondition" property as per schema. I will check with Jason(
> Who wrote the logService) and get back on this.
> BTW can you give me how this information is fetched in IBM way of
> LogService implementation( D-Bus)? If you already ratified any such, i
> think we can leverage. If not, We work together for solution.
>> * Any plan to add resource path in this journal message which
>> tells that this is the path for which resource created event
> Same as above.
>> * Would the path be "Redfish Path/ D-bus Path"?
> As per Redfish specification, This should be "@odata.id" which means
> it should be of resource uri and so we can't use d-bus path here for
>> * Where the mapping would be done between D-busPath/Redfish
>> Resource path?
>> Cons: Every application have to make the change(use sd_journal_send).
>> My thought is backend application should not be aware of the redfish terminlogy.
> Having separate process only for this mapping may not be good( No
> different from maintaining that map inside bmcweb as there won't be
> any other consumers). Ideal way is, that should be mapped while
> logging logEntry's itself. But we are not doing it currently which
> need to be re-looked. Give me some time, I will think and check with
> other folks and get back.
>> *2.* Some application(bmcweb) would do the Inotify on the
>> path(/var/log/redfish) and send the event once there is any activity
>> on this file.
>> > I thought we can have mapping in bmcweb for ResourceTypes with set of MessageID's for Logged events ( As
>> per Intel design)
>> Can you explain more here. What is your plan? How you would do the Resource Type based event filtering?REDFISH_MESSAGE_ID is different than the resource type.
> Initially i thought "ResourceType" based event filtering can be done
> using minimal mapping( Using MessageID and args). But that will work
> for minimal set. If the supported ResourceTypes grows, we will have
> bigger challenges which i can sense it now. Anyway, Supported
> Resources are completely implementation specific. If this value is
> empty means, by default all event logs will be sent to subscribers.
> This is what we can start with before supported ResourceTypes list grows.
>>> As per my reading from below query, You are looking at d-bus match
>>> rules and ResourceTypes mapping which is more specific to d-bus
>>> event logging(IBM way of implementing event logging). reading it
>>> from journal logs will give more information but that will impact
>>> the performance to large extent. This might be one of the reason why
>>> we (Intel) uses Redfish message ID while logging redfish events logs
>>> to journal(You can refer design document for same at
>>> In opinion, in your d-bus if you are using some kind of
>>> filter(Example REDFISH_MESSAGE_ID) while logging in journal logs for
>>> all events and figure out the way to monitor the journal logs
>>> without impacting the performance, that should be ok as long as
>>> match filters are satisfied for Redfish EventService subscriptions
>>> and supported Types(Again differs with implementation).
>>> On 2/10/2020 1:52 AM, RAJESWARAN THILLAIGOVINDAN wrote:
>>>> As you have shown interest in this feature and submitted the design
>>>> document, do you have any opinion on this? Do you see any merit in
>>>> using D-Bus match in bmcweb to create event logs for life cycle
>>>> events? Please feel free to weigh in.
>>>> On 01-02-2020 02:23, RAJESWARAN THILLAIGOVINDAN wrote:
>>>>> I am going through the bmcweb code for implementing Redfish
>>>>> EventService based on the design document
>>>>> https://gerrit.openbmc-project.xyz/c/openbmc/docs/+/24749. This
>>>>> design is hooked to the journal based Redfish Event Logging. For
>>>>> life cycle events(ResourceAdded, ResourceRemoved,
>>>>> ResourceUpdated), using D-Bus match, bmcweb can create an event
>>>>> log. This requires a JSON dictionary, comprising an array of
>>>>> Redfish Resource Name and the D-Bus path. This approach works only
>>>>> in case of one to one mapping of Redfish Resource Name and the
>>>>> D-Bus path. For propertiesChanged events, if the Redfish Resource
>>>>> property is not on the same D-Bus path or the Redfish Resource
>>>>> property name is different from the D-Bus property name, then an
>>>>> additional JSON dictionary to maintain this information is
>>>>> required. With D-Bus match alone in the bmcweb, Redfish
>>>>> EventService can't be fully supported. For the Message Registers
>>>>> and the Resource Types that are supported, the relevant OpenBMC
>>>>> application must create an event log in the journal using either
>>>>> the phosphor::logging::entry or sd_journal_send() command.
>>>>> After realizing that with D-Bus match in the bmcweb alone can't
>>>>> help to fully implement EventService, I prefer to avoid using
>>>>> D-Bus match in bmcweb. Instead, I prefer to modify the OpenBMC
>>>>> application that generated the event to create an event log in the
>>>>> journal. Do you see any advantage of using combination of D-Bus
>>>>> match in the bmcweb wherever it is possible and changes to OpenBMC
>>>>> application in other cases to create an event log ?
>>>>> Your views are highly appreciated.
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