8.1. FreeSWITCH integration

Being the original platform supported by CGRateS, FreeSWITCH has the advantage of support for complete set of CGRateS features. When used as Telecom Switch it fully supports all rating modes: prepaid/postpaid/pseudoprepaid/rated. A typical use case would be like the one in the diagram below:

_images/CGRateSFSTypicalUsage.png

The process of rating is decoupled into two different components:

8.1.1. SessionManager

TODO - update and add CDRs and CDRc.

  • Attached to FreeSWITCH via the socket library, enhancing CGRateS with real-time call monitoring and call control functions.

  • In Prepaid mode implements the following behaviour:
    • On CHANNEL_PARK event received from FreeSWITCH:
      • Authorize the call by calling GetMaxSessionTime on the Rater.
      • Sets the channel variable cgr_notify via uuid_setvar to one of the following values:
        • MISSING_PARAMETER: if one of the required channel variables is missing and CGRateS cannot make rating.
        • SYSTEM_ERROR: if rating could not be performed due to a system error.
        • INSUFFICIENT_FUNDS: if MaximSessionTime is 0.
        • AUTH_OK: Call is authorized to proceed.
      • Un-Park the call via uuid_transfer to original dialed number. The FreeSWITCH administrator is expected to make use of cgr_notify variable value to either allow the call going further or reject it (eg: towards an IVR or returning authorization fail message to call originator).
    • On CHANNEL_ANSWER event received:
      • Index the call into CGRateS’s cache.
      • Starts debit loop by calling at configured interval MaxDebit on the Rater.
      • If any of the debits fail:
        • Set cgr_notify channel variable to either SYSTEM_ERROR in case of errors or INSUFFICIENT_FUNDS of there would be not enough balance for the next debit to proceed.
        • Send hangup command with cause MANAGER_REQUEST.
    • On CHANNEL_HANGUP_COMPLETE event received:
      • Refund the reserved balance back to the user’s account (works for both monetary and minutes debited).
      • Save call costs into CGRateS LogDB.
  • In Postpaid mode:

    • On CHANNEL_ANSWER event received:
      • Index the call into CGRateS’s cache.
    • On CHANNEL_HANGUP_COMPLETE event received:
      • Call Debit RPC method on the Rater.
      • Save call costs into CGRateS LogDB.
  • On CGRateS Shutdown execute, for security reasons, hangup commands on calls which can be CGR related:
    • hupall MANAGER_REQUEST cgr_reqtype prepaid
    • hupall MANAGER_REQUEST cgr_reqtype postpaid

8.1.2. Mediator

TODO - remove this section. Mediator functionality is handled by CDRs and CDRc.

Attaches costs to FreeSWITCH native written .csv files. Since writing channel variables during hangup is asynchronous and can be missed by the CDR recorder mechanism of FreeSWITCH, we decided to keep this as separate process after the call is completed and do not write the costs via channel variables.

8.1.2.1. Modes of operation

The Mediator process for FreeSWITCH works in two different modes:

  • Costs from LogDB (activated by setting -1 as subject_idx in the cgrates.cfg:
    • Queries LogDB for a previous saved price by SessionManager.
    • This behavior is typical for prepaid/postpaid calls which were previously processed by SessionManager and important in the sense that we write in CDRs exactly what was billed real-time from user’s account.
  • Costs queried from Rater:
    • This mode is specific for multiple process mediation and does not necessary reflect the price which was deducted from the user’s account during real-time rating.
    • Another application for this mode is pseudoprepaid when there is no SessionManager monitoring and charging calls in real-time (debit done directly from CDRs).
    • This mode is triggered from configuration file by setting proper indexes (or leave them defaults if cgrates rating template is using whitin FreeSWITCH cdr_csv configuration file.

A typical usage into our implementations is a combination between the two modes of operation (by setting at a minimum -1 as subject_idx to run from LogDB and succesive mediation processes with different indexes).

8.1.2.2. Implementation logic

  • The Mediator process is configured and started in the cgrates.cfg file and is alive as long as the cgr-engine application is on.
  • To avoid concurrency issues, the Mediator does not process active maintained CDR csv files by FreeSWITCH but picks them up as soon as FreeSWITCH has done with them by rotating. The information about rotation comes in real-time on the Linux OS through the use of inotify.
  • Based on configured indexes in the configuration file, the Mediator will start multiple processes for the same CDR.
  • For each mediation process configured the Mediator will apped the original CDR with costs calculated. In case of errors of some kind, the value -1 will be prepended.
  • When mediation is completed on a file, the file will be moved to configured cdr_out_dir path.