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csharp-test-bed-adapter

This is the C# Apache Kafka adapter created for the DRIVER-EU test-bed. This allows C# written programs to communicate over the test-bed.

The implementation is a wrapper around Confluent's .NET Client for Apache KafkaTM with the additional NuGet package to support Avro serialization (Confluent.Kafka.Avro (version 1.0.0-beta2)), and offers support for:

  • Sending and receiving Avro schema's and messages: both producer and consumer use Avro schema's for their message key and value. Methods for sending and receiving standard or custom messages are SendMessage & AddCallback
  • Logging via Kafka: your application can log on several log levels (eg. error, debug, info) onto a specific test-bed topic. Methods for sending and receiving log messages are Log & AddLogCallback
  • Receive time information: the adapter is connected to the test-bed time service, allowing you to receive relevant time-related information like fictive trial time, or the speed of the trial. Method for retrieving the time information is GetTimeInfo
  • Uploading large data: the adapter is connected to the test-bed large data service, allowing you to upload large data files for sharing with other applications connected to the test-bed. Methods for uploading large data are GetLargeFileServiceClient & Upload
  • Setup a SSL connection with a test-bed including security features Setup is completely done in the CSharpTestBedAdapter-settings.xml
  • Internal Management: the adapter makes the coupling between application and test-bed as easy as possible.

Project structure

This project contains one CSharpTestBedAdapter.sln solution, which in its turn contains 7 C# projects:

src\CSharpTestBedAdapter

The main C# project outputting a class library CSharpTestBedAdapter.dll that you can use to create Kafka producers and consumers connecting to the DRIVER-EU test-bed.

examples\CSharpExampleProducer (Custom & Standard)

The examples for setting up and using a producer via the CSharpTestBedAdapter.dll. CSharpExampleProducerCustom sends out a test message that is defined in example\common\CommonMessages. CSharpExampleProducerStandard sends out a Common Alerting Protocol (CAP) message that is defined in example\common\StandardMessages.

examples\CSharpExampleConsumer

The example for setting up and using a consumer via the CSharpTestBedAdapter.dll. This example listens to both the test messages from CSharpExampleProducerCustom and CAP messages from CSharpExampleProducerStandard.

src\CommonMessages

Project that is used in the examples only, containing a simple test Avro schema that is used for transmitting messages of that type from producer to consumer. Inside the examples\common\CommonMessages\data folder you'll find a README regarding the conversion from Avro schema to C# class file(s).

src\CoreMessages

The code project that bundles all system/core message formats defined for the DRIVER-EU Test-bed. These schemas can also be found at DRIVER-EU avro-schemas. This project is required for CSharpTestBedAdapter to run. The following message formats are currently implemented:

  • Heartbeat: sending to topic system_heartbeat This allows the adapter to indicate it is still alive for all other adapters in the test-bed.
  • Log: sending to topic system_logging Both the adapter as your application can send log messages to the test-bed to inform operators on what is going on inside the application.
  • Admin heartbeat: receiving from topic system_admin_heartbeat The adapter checks if the admin tool inside the test-bed is alive. If not during the first 10 seconds of this adapters existence, the adapter will enter DEBUG mode. If the admin tool was present but connection is lost somehow, the adapter will enter DISABLED mode until the admin tool comes back alive, re-sending and re-receiving all messages that were queued during being disabled.
  • Timing: receiving from topic system_timing The time service updates all adapters for setting a global time frame. Current time information can be retrieved from the GetTimeInfo method.
  • Time control: receiving from topic system_timing_control The Trial Management Tool notifies all adapters on time changes, for instance whenever a running trial is paused.

src\StandardMessages

The code project that bundles all standard message formats defined for the Common Information Space (CIS) of the DRIVER-EU Test-bed. All these Avro schemas can be found at DRIVER-EU avro-schemas. This project is required for CSharpTestBedAdapter to run. The following message formats are currently implemented:

src\SimMessages

The code project that bundles all simulation message formats defined for the Common Simulation Space (CSS) of the DRIVER-EU Test-bed. All these Avro schemas can be found at DRIVER-EU avro-schemas. This project is not required for CSharpTestBedAdapter to run.

Dependencies

In order to use the csharp-test-bed-adapter, you are also required to download and install the above-mentioned NuGet package.

Usage

The C# test-bed adapter is available as Nuget package. You can also manually build CSharpTestBedAdapter and include the compiled DLLs CSharpTestBedAdapter.dll, CoreMessages.dll & StandardMessages.dll into your own application.

Next to the compiled CSharpTestBedAdapter.dll, there is a CSharpTestBedAdapter-settings.xml, where you can change the following adapter settings:

  • client.id: the name of the application that uses this adapter
  • heartbeat.interval: the time (in ms) between sending a heartbeat
  • security.protocol: the security protocol this adapter is using (PLAINTEXT or SSL)
  • security.ca.path: the path of the issuer certificate :: only needed when security.protocol = SSL
  • security.keystore.path: the path of the PKCS#12 keystore (client keypair + certificate) for client authentication :: only needed when security.protocol = SSL
  • security.keystore.password: the password for the PKCS#12 keystore :: only needed when security.protocol = SSL
  • broker.url: the URL of the Kafka broker to connect to
  • schema.url: the URL of the schema registry service to use
  • send.sync: indication if the adapter needs to stall the application thread until the message is sent
  • retry.count: number of retries before timing out when sending messages
  • retry.time: amount of time (in ms) before timing out when sending messages
  • direct.connect: indication if this adapter is allowed to send and receive messages without waiting for the admin tool

See the 3 example projects for further implementation of this adapter.

Security

With regards to the security aspect of this adapter, the security.ca.path property must contain a .pem file. This is a text file that contains the concatenated PEM-encoded Certificate Authority (CA) certificate(s) in your adapter’s complete certificate chain. Bear in mind that for this to work properly it is containing the complete chain of the CA:

  • if your certificate is issued by a Root CA, then this .pem file should contain only the Root CA certificate
  • if your certificate is issued by an Intermediate CA, which is issued by a Root CA (this is currently the case within the DRIVER+ Test-bed), then this .pem file should contain the Root CA certificate and the Intermediate CA certificate

Because of a flaw inside the librdkafka DLL used inside the C# adapter, this complete chain needs to be generated manually in order to work with Intermediate CA certificates inside the .pem file. You can create this .pem file by extracting the certificate chain from the .p12, with a key management tool like openssl (or keytool):

$ openssl pkcs12 -in <your p12 keystore> -cacerts -nokeys -chain > ca_certs.pem

For more information on security within the DRIVER+ Test-bed, please see this repository.

Data conversion between Avro and C#

This functionality ensures proper conversion from Avro schemas to C# classes. It uses the avrogen.exe that is built from the Apache Avro GitHub.

Core, Standard & Sim Avro schemas

Within this adapter, all core, standard and sim Avro schemas defined in the DRIVER-EU avro-schemas repository are already converted for ease of use. If you want to re-convert these schemas, you can run the convert.bat Windows batch file in the folder src\CoreMessages\data\avro-schemas for the core adapter messages, src\StandardMessages\data\avro-schemas for the standard messages, and src\SimMessages\data\avro-schemas for the simulation messages.

Conversion of custom schemas

Conversion from Avro schema to C# class file requires the following files, which can be found at src\CoreMessages\data\avro-schemas or src\StandardMessages\data\avro-schemas:

  • The compiled avrogen.exe (source) and its required DLLs
  • The Windows batch file convert.bat that calls the avrogen.exe with the correct parameters for converting all present Avro schemas to corresponding C# class file(s). You can edit this batch file to convert your own Avro schemas.