| Instant module | ||
|---|---|---|
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iKnowBase comes with client and server side support for creating applications with real time asynchronous messaging support. The Instant server is implemented as a java module in the iknowbase-webapp application.
See the Development Guide#Using Instant for concept and examples.
The Instant Server is disabled by default, but can be enabled and configured using configuration properties.
Make sure that CORS is enabled in configuration id the clients use Instant on a different name or port than what is used for fetching content from iKnowBase Viewer.
Make sure you also configure the SecureTokenEngine InstallationGuide#SecureTokenEngine to enable web client single sign on between iKnowBase Viewer and Instant. An alternative without single sign on between iKnowBase Viewer and Instant is to use explicit login – see Authenticating with direct application container authentication .
The connected web-clients will be “always connected” using asycnchronous HTTP transport mechanisms and will, compared to traditional HTTP clients, need infrastructure with support for non-blocking I/O or a sufficient high number of supported concurrent connections. One Instant client subscription means one network connection. ikbInstant may be deployed on an application server separate from where the other iKnowBase applications are deployed, as long as it’s connected to the same iKnowBase database repository.
If Cross Origin Resource Sharing (CORS) is in use, the CORS address MUST use the same protocol as the webpage containing the JavaScript client. If the web page uses HTTPS, then the CORS address must also be HTTPS.
The Instant Server is disabled by default and must be explicitly enabled using configuration properties. The InstantServerConfiguration accepts these configuration properties:
| Property name | Description |
|---|---|
| com.iknowbase.instant.enabled | Toggles whether the instant module is enabled. |
| com.iknowbase.instant.suspendTimeoutLP | How long in miliseconds a Long Polling connection is suspended before the server resumes the connection. This will trigger a reconnect by the client. |
| com.iknowbase.instant.enableCORSFilter | Server side support for Cross Origin Resource Sharing (CORS). The legal values are either “true” or “false”. |
| com.iknowbase.instant.cleanupTopicThreshold | How often the disconnect cleanup maintenance thread looks for disconnected clients. |
| com.iknowbase.instant.cleanupDisconnectedConnectionsThreshold | How long a connection needs to be in disconnect inactivity queue before it is examined and validated. |
| com.iknowbase.instant.broadcastDelayUserListUsers | Delay between a client subscribe and the issued broadcast for userList is. Must be large enough to allow the client to complete the handshake and enter suspend mode. |
| com.iknowbase.instant.broadcastDelayUserListJoin | Optional delay between a detected join and the issued broadcast. Default no delay. |
| com.iknowbase.instant.broadcastDelayServerRequest | Optional delay between a serverRequest and the issued broadcast. Default no delay. |
Note: Make sure you also configure SecureTokenEngine to enable authentication for web clients
The Instant Queue Server is the unit responsible for consuming messages published using Instant’s PL/SQL API and delivering them to the specified topic where all web clients are connected. This queue listener can of course be configured through The InstantQueueServerConfiguration which accepts these configuration properties:
| Property name | Description |
|---|---|
| com.iknowbase.instant.aq.enabled | Toggles whether AQ messages is processed by this instance at all. The legal values are either “true” or “false”. |
| com.iknowbase.instant.aq.dequeTimeoutSeconds | Number of seconds each dequeue() shall wait before recycyling. |
| com.iknowbase.instant.aq.spawnPolicy | Decides when the AQ server starts listening for a new message. Use “immediate” for parallel processing, or “delayed” for serial processing. |
For developers, the Administration Console provides monitoring and testing details for Instant.
You may encounter a session cookie collision if you
As the host name is the same for both requests, the session cookie name will by default be valid for both requests. The session cookie is only valid on one server, which will result in a replaced session cookie and effective log out the authenticated user.
Resolve the issue by changing the session cookie name for one of the applications or use different hostnames for accessing the applications.
This warning can safely be ignored.
The current Atmosphere library incorrectly switches to BlockingIO if JSR356AsyncSupport is not available.
ERROR DefaultAsyncSupportResolver - Failed to create comet support class: class org.atmosphere.container.JSR356AsyncSupport, error: java.lang.reflect.InvocationTargetException
ERROR DefaultAsyncSupportResolver - Switching to BlockingIO
This has been registered as Atmosphere Issue 2018 and fixed for future versions. iKnowBase 7.0 ships with a workaround to avoid BlockingIO and you should see the previous ERROR messages immediately followed by:
WARN IKBAsyncSupportResolver - Atmosphere issue 2018 detected. Overriding asyncSupport class from BlockingIOCometSupport to Servlet30CometSupport to avoid Blocking IO
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