Function cont_check_cacheable

plugins/background_fetch/background_fetch.cc:463–501

////////////////////////////////////////////////////////////////////// This is a TXN hook, used to verify that the response (before sending to originating client) is indeed cacheable. This has to be deferred, because we might have plugins that changes the cacheability of an Origin response.

// we might have plugins that changes the cacheability of an Origin response.
//
static int
cont_check_cacheable(TSCont contp, TSEvent /* event ATS_UNUSED */, void *edata)
{
  // ToDo: If we want to support per-remap configurations, we have to pass along the data here
  TSHttpTxn txnp = static_cast<TSHttpTxn>(edata);
  TSMBuffer response, request;
  TSMLoc    resp_hdr, req_hdr;

  if (TS_SUCCESS == TSHttpTxnServerRespGet(txnp, &response, &resp_hdr)) {
    if (TS_SUCCESS == TSHttpTxnClientReqGet(txnp, &request, &req_hdr)) {
      // Temporarily change the response status to 200 OK, so we can reevaluate cacheability.
      TSHttpHdrStatusSet(response, resp_hdr, TS_HTTP_STATUS_OK);
      bool cacheable = TSHttpTxnIsCacheable(txnp, nullptr, response);
      TSHttpHdrStatusSet(response, resp_hdr, TS_HTTP_STATUS_PARTIAL_CONTENT);

      Dbg(Bg_dbg_ctl, "Testing: request / response is cacheable?");
      if (cacheable) {
        BgFetchData *data = new BgFetchData();

        // Initialize the data structure (can fail) and acquire a privileged lock on the URL
        if (data->initialize(request, req_hdr, txnp) && data->acquireUrl()) {
          data->schedule();
        } else {
          delete data; // Not sure why this would happen, but ok.
        }
      }
      // Release the request MLoc
      TSHandleMLocRelease(request, TS_NULL_MLOC, req_hdr);
    }
    // Release the response MLoc
    TSHandleMLocRelease(response, TS_NULL_MLOC, resp_hdr);
  }

  // Reenable and continue with the state machine.
  TSContDestroy(contp);
  TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);

  return 0;
}

//////////////////////////////////////////////////////////////////////////////
// Main "plugin", which is a global READ_RESPONSE_HDR hook. Before