We have an application that must connect to multiple graph DBs. The database that we want to connect to can be determined in the header of an HTTP request.
I have tried writing an HandlerInterceptorAdapter and auto wiring the SessionFactory and then building a Configuration with the proper URI for the graph I want to connect to. Then I used sessionFactor.getDriver().configure(newConfiguration). This worked for the first call, but every subsequent call failed with a message stating the driver was closed.
Is it possible to do such a thing with Spring Data Neo4J?
Spring Data Neo4j has no support for this feature. In general the whole connection and class scanning mechanism will start when your application starts. Altering the configuration during runtime is not intended.
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I am trying to use an UWP app service to provide some non-UI processing service to other app including the host app. For responsiveness, I want to return the result progressively. Think about grep-ping a folder for files containing a certain string: It would be better to report the files as we found it instead of reporting everything at the end.
So my question is: Can this scenario be achieved with the current UWP technology? (I think it is probably possible via polling using the multiple app instances approach. I want to know if there's an easier method with app service.)
The AppServiceConnection is a bi-directional communication pipe, so you can use it to communicate progress updates from the service to the client. No need for polling. Just retain a reference to the AppServiceConnection instance in your service implementation once the client has connected and then call SendMessageAsync to send progress updates to client whenever you want.
We have a working setup of 3 peer nodes and a multi user rest server running on 1 of the peers. Now there are multiple user cards created and imported in the rest server(using web based client) which is working fine. I can trigger transactions and query the blockchain with it.
However In case I need to upgrade my network and there is some change in model file(i.e. any participant/asset/transaction parameters changes). I need to restart rest server so that effect can be observed by WEB based client application. So my questions are:
1. Is there a way to upgrade Rest interfaces without restarting the server.
2. In case Rest server crashed or restarted is there some way to use the old cards that were created before server shutdown.
When the REST server starts you can see that it "discovers" the Business Network and then generates the End Points. The discovery is not dynamic, so that when you change the model or other element of a BNA you need to restart the REST server to re-discover the updated network. (In a live scenario I would think changes to the model are infrequent.)
Are you using multi-user mode for the REST server? Assuming that you are, then Configuring the REST server with a persistent Data Source as described in the documentation, or this tutorial should solve the problem of re-importing the cards. You could also "backup" the cards after they have been used the first time by Exporting them.
I am using Datastax's c++ driver version 2.8.0 for Apache Cassandra inside a kubernetes application. Cassandra is deployed as a 3 node cluster via this Helm chart.
The chart leverages kubernetes' headless services to make the Cassandra endpoints available, so there is an entry in the kubernetes DNS for those endpoints.
I have a c++ app running in a kubernetes pod that interacts with Cassandra, which connects using that DNS entry to resolve the endpoints. The application has a single connection to Cassandra object, following the driver usage guidelines. Connection is initialized at the beginning of the program, and failure to initialize the connection or to execute a query later on will actually fail the program.
Everything is working fine, but cassandra nodes/pods may eventually go down for some reason. When that happens, they're respawned, but get reassigned with a different IP. It seems like the c++ driver is able to get the new endpoints from the DNS without any additional code. However in such a situation the connection is not closed on the client side, and it looks like the previous endpoints remain in the connection pool on some level. This leads to a series of log events similar to the following:
1531920921.161 [WARN] (src/pool.cpp:420:virtual void cass::Pool::on_close(cass::Connection*)): Connection pool was unable to reconnect to host XXX.XXX.XXX.XX because of the following error: Connection timeout
and
1531920921.894 [WARN] (src/pool.cpp:420:virtual void cass::Pool::on_close(cass::Connection*)): Connection pool was unable to reconnect to host XXX.XXX.XXX.XX because of the following error: Connect error 'host is unreachable'
Which pop up every [reconnect timeout]. The more IP reassignments, the more log messages, which as you can guess can get to a pretty large number for long lived applications.
Is there some feature of the driver's API that allows dealing with that? Or a good/recommended way to handle that client side, more generally? One option, external to the driver, could be to reset the connection within the client code, but (although I may be missing out) I fail to see a way to "catch" such events : they only show up in the logs.
I am working on an application which consists of 2 layers: The GUI built in Electron and the "backend" built in C++ running in the background. The GUI needs to be able to (amongst other things such as streaming data) send and request data to and from the backend for configuration purposes. For communication Redis is being used, mainly for its pub/sub capability.
What would be the preferred way to request and send data from/to the backend? I came up with the following ideas but I'm not sure if any of these are the way to go.
Publish value on a configuration channel and handle the request via switch case. E.g. configuration.set_sensor_frequency is handled by a set_sensor_frequency(value) function in the backend.
Write the configuration to configuration.sensor_frequency on the redis server and listen to the set event on the backend and react accordingly. But this kinda seems like method 1 but more complicated.
Like method 2, write the config to the redis server and periodically check (every few cycles or so) in the backend whether the value has been updated
Something else. Please elaborate.
I have a Delphi Application accessing a web service on the Internet.
The provider of said service has now changed to a cloud based infrastructure and came to me with the following request:
"Please configure networkaddress.cache.ttl in the file $JAVA_HOME/jre/lib/security/java.security as follows: networkaddress.cache.ttl=60"
Accordung to the web service provider this is necessary for the service to deliver correct results under all circumstances.
He has checked the connection of my appication and it appears to him that once started it sticks with the same IP-address.
Restarting the Applications did solve this for once.
I have been importing the WSDL using the wizard provided by the IDE so I am using an instance of THTTPRIO to access the web service.
The THTTPRIO-instance is created in FormCreate() of the main form.
The Application is running 24/7 and accesses several methods of the web service regularly.
Does the Delphi SOAP framwork use DNS caching at all?
If yes, is there a similar property like networkaddress.cache.ttl in Java?
Is there a good workaround for the issue (e.g. reinstancing the wrapper class just before every call to the service instead of only once in FormCreate)?
EDIT:
The Application is compiled using Delphi 10.1. Berlin (originally developed with Delphi XE7). It is running on an Windows 7 machine.
Have you found DnsFlushResolverCache?
In order to clear DNS resolver cache like what IPCONFIG /flushdns
does, programmatically:
Requires dnsapi.dll which requires Win2000 or later. As usual, MS does
not document the API
Source: http://brannockdevice.blogspot.de/2006/04/winxp-flushing-dns-programatically.html
I've been digging into the source code a little and I believe I found an answer.
The Delphi SOAP framwork doesn't seem to do any DNS caching on its own.
It's just that the connection to the web service is done with the first request via the Windows InternetConnect() function and the resulting handle ist stored and reused from then on.
Here's a little more background information on this:
The THTTPRIO class communicates with the web service through an instance of THTTPReqResp:
property HTTPWebNode: THTTPReqResp read GetHTTPWebNode write SetHTTPWebNode;
THTTPReqResp calls the Connect() method before every request which again uses a WinApi function to estabish a connection and stores the resulting handle in a field:
FInetConnect := InternetConnect(FInetRoot, PChar(FURLHost), FURLPort, PChar(FUserName), PChar(FPassword), INTERNET_SERVICE_HTTP, 0, NativeUInt(Self));
But - the Connect() method only does this if it is not already connected - the following code is found just at the beginning of the Connect() method:
if (FConnected) then
Exit;
By doing so the connection just stays open from the first request on.
Following requests are simply using the stored handle from InetConnect.
For my problem with the cloud service it should be sufficient to create my own instance of THTTPRIO and pass it to the function returning the web service interface:
RIO := THTTPRIO.Create(nil);
FM := GetFleetManagerAPISoap(FALSE, '', RIO);
Then I will just disconnect each time before calling any web service function:
RIO.HTTPWebNode.Connect(FALSE);
In theory that should finally lead to a fresh connection via InternetConnect() and hopefully my problem will be solved.
(Still have to test this, though)
I think that you can set it globally in Windows registry.
Open regedit.exe and navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters.
In the right pane, add the following value:
Name: DefaultTTL,
Type: REG_DWORD,
Valid Range: 1-255
Restar the computer.
https://technet.microsoft.com/en-us/library/cc957530.aspx