Looking for more information or at least suggestions on alternatives to EventRecordID as an index when using the Windows Event Collector.
When working with an individual server and individual Eventlog, the EventRecordID element can be used as an index to keep your place when crawling through events in order.
However, when using the Windows Event Collector, the events retain their original EventRecordID in the ForwardedEvents log. That makes it difficult at best to keep track of where you were when crawling through events with a script/program.
The date/timestamp doesn't help either, as events can come in from other systems after you have moved past a given date/time.
Does anyone have any suggestions on a way to track, bookmark, or index events in ForwardedEvents?
You can use the BookmarkID
See how to get it with the Microsoft example in C++ here
or like I did with C#
EventLogQuery eventsQuery = new EventLogQuery("ForwardedEvents", PathType.LogName);
EventLogReader logReader = new EventLogReader(eventsQuery);
EventRecord myevent = logReader.ReadEvent();
string bookmark = ReflectionHelper.GetPropertyValue(myevent.Bookmark, "BookmarkText").ToString();
ReflectionHelper is not from me. Source here
Related
New to Masstransit here and I wanted to correlate my message with an int value (let's call it OrderId of type INT. I will use the same order management example from Masstransit).
I wanted to see if anyone was able to use an int to correlate events and messages in Masstransit.
I used this code in my events (both the events)
x.CorrelateById<int>(state => state.OrderId, context => context.Message.OrderId)
This compiles fine but then throws and exception
NotImplementedByDesignException. Masstransit doc says : "Redis only supports event correlation by CorrelationId, it does not support queries. If a saga uses expression-based correlation, a NotImplementedByDesignException will be thrown."
I am using CorrelateById() so not sure why I am seeing this exception. I don't see any query here (or is it this func that returns the OrderId? The correlationId has a similar expression although it takes only one argument of type: Func<ConsumeContext<TMessage>, Guid> selector)
All I want is to be able to correlate message and event by an Int prop coming to my first event of the state machine. (That I have no control over by the way).
I feel creating another GUID just for Masstransit and link it to that OrderId is not the best option here.
My other question: is there any out of the box way in MassTransit to get the all event data for a specific CorrelationId (event sourcing style). I saw there was a MassTransit.EventStoreIntegration repo on github but since we can get the last version of the state instance I thought there would be a way to see all state instances/ or messages being persisted then pulled.
Sure I can see that in the log but I would like to see only the state changes that were pushed.
Thanks
Correlation by anything other than the Guid CorrelationId property is a query. And, as you've found out, Redis doesn't support queries. If you need to correlate events using a type other than a Guid, Redis is not an option.
As per #Chris answer, and because I wanted to use an INT property and still use redis, I used Guid CorrelationId that was generated from that INT value with padded zeros.
CorrelationId = new Guid(OrderIdIntValue.ToString().PadLeft(32, '0'))
I am aware of the Guid vs int discussion in distributed systems.
For my case this works with no issues since that Int value is generated by a unique source of truth (that I consume and don't have control over).
I am writing an application for my own purposes that aims to get play pause events no matter what is going on in the system. I have gotten this much working
let commandCenter = MPRemoteCommandCenter.shared()
commandCenter.togglePlayPauseCommand.isEnabled = true
commandCenter.togglePlayPauseCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("Play Pause Command")
return .success
}
commandCenter.nextTrackCommand.isEnabled = true
commandCenter.nextTrackCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("NextTrackCommand")
return .success
}
commandCenter.previousTrackCommand.isEnabled = true
commandCenter.previousTrackCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("previousTrackCommand")
return .success
}
commandCenter.playCommand.isEnabled = true
commandCenter.playCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("playCommand")
return .success
}
MPNowPlayingInfoCenter.default().playbackState = .playing
Most of those methods are there because apparently you will not get any notifications without having nextTrackCommand or previousTrackCommand or playCommand implemented.
Anyways my one issue is that as soon as you open another application that uses audio these event handlers stop getting called and I cant find a way to detect and fix this.
I would normally try doing AVAudioSession things to state this as a background application however that does not seem to work. Any ideas on how I can get playpause events no matter what state the system is in?
I would like to be able to always listen for these events OR get an indication of when someone else has taken control of the audio? Perhaps even be able to re-subscribe to these play pause events.
There's an internal queue in the system which contains all the audio event subscribers. Other applications get on top of it when you start using them.
I would like to be able to always listen for these events
There's no API for that but there's a dirty workaround. If I understand your issue correctly, this snippet:
MPNowPlayingInfoCenter.default().playbackState = .paused
MPNowPlayingInfoCenter.default().playbackState = .playing
must do the trick for you if you run it in a loop somewhere in your application.
Note that this is not 100% reliable because:
If an event is generated before two subsequent playbackState state changes right after you've switched to a different application, it would still be catched by the application in the active window;
If another application is doing the same thing, there would be a constant race condition in the queue, with unpredictable outcome.
References:
Documentation for playbackState is here;
See also a similar question;
See also a bug report for mpv with a similar
issue (a pre-MPRemoteCommandCenter one, but still very valuable)
OR get an indication of when someone else has taken control of the audio
As far as I know there's no public API for this in macOS.
I am making an addon in Firefox, so I have a ChromeWorker - which is a privileged WebWorker. This is just a thread other then the mainthread.
In here I have no code but this (modified to make it look like not js-ctypes [which is the language for addons])
On startup I run this code, conn is a global variable:
conn = xcb_connect(null, null);
Then I run this in a 200ms interval:
evt = xcb_poll_for_event(conn);
console.log('evt:', evt);
if (!evt.isNull()) {
console.log('good got an event!!');
ostypes.API('free')(evt);
}
However evt is always null, I am never getting any events. My goal is to get all events on the system.
Anyone know what can cause something so simple to not work?
I have tried
xcb_change_window_attributes (conn, screens.data->root, XCB_CW_EVENT_MASK, values);
But this didn't fix it :(
The only way I can get it to work is by doing xcb_create_window xcb_map_window but then I get ONLY the events that happen in this created window.
You don't just magically get all events by opening a connection. There's only very few messages any client will receive, such as client messages, most others will only be sent to a client if it explicitly registered itself to receive them.
And yes, that means you have to register them on each and every window, which involves both crawling the tree and listening for windows being created, mapped, unmapped and destroyed and registering on them as well.
However, I would reconsider whether
My goal is to get all events on the system.
isn't an A-B problem. Why do you "need" all events? What do you actually want to do?
I'm looking to develop a chat application with Pubnub where I want to make sure all the chat messages that are send is been stored in the database and also want to send messages in chat.
I found out that I can use the Parse with pubnub to provide storage options, But I'm not sure how to setup those two in a way where the messages and images send in the chat are been stored in the database.
Anyone have done this before with pubnub and parse? Are there any other easy options available to use with pubnub instead of using parse?
Sutha,
What you are seeking is not a trivial solution unless you are talking about a limited number of end users. So I wouldn't say there are no "easy" solutions, but there are solutions.
The reason is your server would need to listen (subscribe) to every chat channel that is active and store the messages being sent into your database. Imagine your app scaling to 1 million users (doesn't even need to get that big, but that number should help you realize how this can get tricky to scale where several server instances are listening to channels in a non-overlapping manner or with overlap but using a server queue implementation and de-duping messages).
That said, yes, there are PubNub customers that have implemented such a solution - Parse not being the key to making this happen, by the way.
You have three basic options for implementing this:
Implement a solution that will allow many instances of your server to subscribe to all of the channels as they become active and store the messages as they come in. There are a lot of details to making this happen so if you are not up to this then this is not likely where you want to go.
There is a way to monitor all channels that become active or inactive with PubNub Presence webhooks (enable Presence on your keys). You would use this to keep a list of all channels that your server would use to pull history (enable Storage & Playback on your keys) from in an on-demand (not completely realtime) fashion.
For every channel that goes active or inactive, your server will receive these events via the REST call (and endpoint that you implement on your server - your Parse server in this case):
channel active: record "start chat" timetoken in your Parse db
channel inactive: record "end chat" timetoken in your Parse db
the inactive event is the kickoff for a process that uses start/end timetokens that you recorded for that channel to get history from for channel from PubNub: pubnub.history({channel: channelName, start:startTT, end:endTT})
you will need to iterate on this history call until you receive < 100 messages (100 is the max number of messages you can retrieve at a time)
as you retrieve these messages you will save them to your Parse db
New Presence Webhooks have been added:
We now have webhooks for all presence events: join, leave, timeout, state-change.
Finally, you could just save each message to Parse db on success of every pubnub.publish call. I am not a Parse expert and barely know all of its capabilities but I believe they have some sort or store local then sync to cloud db option (like StackMob when that was a product), but even if not, you will save msg to Parse cloud db directly.
The code would look something like this (not complete, likely errors, figure it out or ask PubNub support for details) in your JavaScript client (on the browser).
var pubnub = PUBNUB({
publish_key : your_pub_key,
subscribe_key : your_sub_key
});
var msg = ... // get the message form your UI text box or whatever
pubnub.publish({
// this is some variable you set up when you enter a chat room
channel: chat_channel,
message: msg
callback: function(event){
// DISCLAIMER: code pulled from [Parse example][4]
// but there are some object creation details
// left out here and msg object is not
// fully fleshed out in this sample code
var ChatMessage = Parse.Object.extend("ChatMessage");
var chatMsg = new ChatMessage();
chatMsg.set("message", msg);
chatMsg.set("user", uuid);
chatMsg.set("channel", chat_channel);
chatMsg.set("timetoken", event[2]);
// this ChatMessage object can be
// whatever you want it to be
chatMsg.save();
}
error: function (error) {
// Handle error here, like retry until success, for example
console.log(JSON.stringify(error));
}
});
You might even just store the entire set of publishes (on both ends of the conversation) based on time interval, number of publishes or size of total data but be careful because either user could exit the chat and the browser without notice and you will fail to save. So the per publish save is probably best practice if a bit noisy.
I hope you find one of these techniques as a means to get started in the right direction. There are details left out so I expect you will have follow up questions.
Just some other links that might be helpful:
http://blog.parse.com/learn/building-a-killer-webrtc-video-chat-app-using-pubnub-parse/
http://www.pubnub.com/blog/realtime-collaboration-sync-parse-api-pubnub/
https://www.pubnub.com/knowledge-base/discussion/293/how-do-i-publish-a-message-from-parse
And we have a PubNub Parse SDK, too. :)
I am new to Windows Phone 8 development and I'm trying to use the GeoCoordinateWatcher class to easily get the latitude and longitude of the user.
My problem is that I want to manage a timeout (the user will be able to customize its value).
I thought the "TryStart(...)" method would help me to do that, but:
tryStart(false, TimeSpan.FromSeconds(10)); => The watcher starts after 10sec
tryStart(false, TimeSpan.FromSeconds(2)); => The watcher starts after 2sec
This method is, for me, pointless as I want the GeoCoordinateWatcher to start immediately (so I'm using the basic method "Start()", but I also want to return an exception like "The timeout has expired" if it takes more than xxx seconds to return coordinates.
Is there an easy way to do that ? Do I have to create a timer or something like that ?
Thanks a lot for your help
If you are using Windows Phone 8, you should use Geolocation API which is a part of Windows Phone Runtime
http://msdn.microsoft.com/en-us/library/windowsphone/develop/windows.devices.geolocation.geolocator.getgeopositionasync.aspx
This provides a simple / easy way to get location without mucking around.
You might want to go through my verbose blog post on possible issues.
http://invokeit.wordpress.com/2013/05/01/geolocator-and-movementthreshold-wpdev-win8dev/