[jira] [Resolved] (TS-4570) Return to TS_HTTP_OS_DNS_HOOK after explicit DNS

["James Peach (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TS-4570?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

James Peach resolved TS-4570.
-----------------------------
       Resolution: Fixed
         Assignee: James Peach
    Fix Version/s:     (was: sometime)
                   7.0.0

> Return to TS_HTTP_OS_DNS_HOOK after explicit DNS
> ------------------------------------------------
>
>                 Key: TS-4570
>                 URL: https://issues.apache.org/jira/browse/TS-4570
>             Project: Traffic Server
>          Issue Type: Improvement
>          Components: Core, TS API
>            Reporter: James Peach
>            Assignee: James Peach
>             Fix For: 7.0.0
>
>
> Consider the case of a plugin that has out -of-band routing knowledge equivalent to DNS. So for a domain, it might have a number of possible IP addresses. Remap plugins can implement {{TSRemapOSResponse}}, which is called in the connection result handling path, but there's no facility for global plugins to reroute the request.
> In my case, I'm largely doing forward proxying, so I don't have a remap rule for everything I need to route. Hence I'm a global plugin.
> Here is a relatively hacky patch that backs the state machine back up to {{TS_HTTP_OS_DNS_HOOK}} if we get a connection failure, have retries left, and a plugin has called {{TSHttpTxnServerAddrSet}}.
> {code}
> $ git diff proxy/http/HttpTransact.cc
> diff --git a/proxy/http/HttpTransact.cc b/proxy/http/HttpTransact.cc
> index 5ef0430..3363af1 100644
> --- a/proxy/http/HttpTransact.cc
> +++ b/proxy/http/HttpTransact.cc
> @@ -3762,6 +3762,11 @@ HttpTransact::handle_response_from_server(State *s)
>          // families - that is locked in by the client source address.
>          s->state_machine->ua_session->set_host_res_style(ats_host_res_match(&s->current.server->dst_addr.sa));
>          TRANSACT_RETURN(SM_ACTION_DNS_LOOKUP, OSDNSLookup);
> +      } else if (s->api_server_addr_set) {
> +        // If the address was set by a plugin, give it another chance.
> +        s->dns_info.os_addr_style = DNSLookupInfo::OS_ADDR_TRY_HOSTDB;
> +        s->current.attempts++;
> +        TRANSACT_RETURN(SM_ACTION_API_OS_DNS, OSDNSLookup);
>        } else if ((s->dns_info.srv_lookup_success || s->host_db_info.is_rr_elt()) &&
>                   (s->txn_conf->connect_attempts_rr_retries > 0) &&
>                   (s->current.attempts % s->txn_conf->connect_attempts_rr_retries == 0)) {
> {code}
> Note that some plugins might be unprepared for {{TS_HTTP_OS_DNS_HOOK}} to be called multiple times, so we should document that.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)