[jira] [Commented] (TS-2458) the http transaction should not be rescheduled when the original connections overflow

["Leif Hedstrom (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TS-2458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13859602#comment-13859602 ] 

Leif Hedstrom commented on TS-2458:
-----------------------------------

Hmmm, not sure I agree that we should "cut off" transactions immediately. The purpose here is to deal with spiky traffic, afaik, and giving error pages seems draconian. Maybe it could be a configuration options, with a default of 100ms, and setting it to 0 means "cut off" immediately. For someone running into serious problems, they could also bump it up to a higher value, say 1000ms.

If we made this overridable, a plugin could also be smart about this, and make the back off time dynamic. Start with 100ms, as we accumulate more and more, bump it up to towards some max number (say 2000ms), and after that, start killing transactions immediately. The point would be though that some basic capability is records.config'urable, and more advanced behavior like the above could be achieved via a plugin.

Thoughts?


> the http transaction should not be rescheduled when the original connections overflow
> -------------------------------------------------------------------------------------
>
>                 Key: TS-2458
>                 URL: https://issues.apache.org/jira/browse/TS-2458
>             Project: Traffic Server
>          Issue Type: Improvement
>          Components: HTTP
>            Reporter: Yu Qing
>
> we have origin connections limits, the parameter proxy.config.http.server_max_connections is for whole connections, and the parameter proxy.config.http.origin_max_connections is for the specified connections per original server ip / host.
> the http transaction is rescheduled / retried after 100ms  when it's original connections exceed these limits.
> these transactions will be rescheduled repeatly when the original server is very slow. the system worsens when these retries happen because the http transactions accumulate more and more. 
> I think we should cut off these transactions immediately other than retry after 100ms.
> the rescheduling codes in proxy/http/HttpSM.cc as:
> 4581     if (sum >= t_state.http_config_param->server_max_connections) {
> 4582       ink_assert(pending_action == NULL);
> 4583       pending_action = eventProcessor.schedule_in(this, HRTIME_MSECONDS(100));
> 4584       httpSessionManager.purge_keepalives();
> 4585       return;
> 4586     }
> 4587   }
> 4588   // Check to see if we have reached the max number of connections on this
> 4589   // host.
> 4590   if (t_state.txn_conf->origin_max_connections > 0) {
> 4591     ConnectionCount *connections = ConnectionCount::getInstance();
> 4592 
> 4593     char addrbuf[INET6_ADDRSTRLEN];
> 4594     if (connections->getCount((t_state.current.server->addr)) >= t_state.txn_conf->origin_max_connections) {
> 4595       DebugSM("http", "[%" PRId64 "] over the number of connection for this host: %s", sm_id,
> 4596         ats_ip_ntop(&t_state.current.server->addr.sa, addrbuf, sizeof(addrbuf)));
> 4597       ink_assert(pending_action == NULL);
> 4598       pending_action = eventProcessor.schedule_in(this, HRTIME_MSECONDS(100));
> 4599       return;
> 4600     }
> 4601   }



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