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https://issues.apache.org/jira/browse/TS-4331?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15315282#comment-15315282
]
ASF GitHub Bot commented on TS-4331:
------------------------------------
Github user jacksontj commented on a diff in the pull request:
https://github.com/apache/trafficserver/pull/653#discussion_r65796064
--- Diff: iocore/hostdb/HostDB.cc ---
@@ -1593,29 +1437,21 @@ HostDBContinuation::dnsEvent(int event, HostEnt *e)
}
}
}
- } else {
- for (ii = 0; ii < nn; ++ii) {
- if (is_addr_valid(af, e->ent.h_addr_list[ii])) {
- HostDBInfo &item = rr_data->info[i];
- memset(&item, 0, sizeof(item));
- ip_addr_set(item.ip(), af, e->ent.h_addr_list[ii]);
- item.full = 1;
- item.round_robin = 0;
- item.round_robin_elt = 1;
- item.reverse_dns = 0;
- item.is_srv = 0;
- item.md5_high = r->md5_high;
- item.md5_low = r->md5_low;
- item.md5_low_low = r->md5_low_low;
- item.hostname_offset = 0;
- if (!restore_info(&item, old_r, old_info, old_rr_data)) {
- item.app.allotment.application1 = 0;
- item.app.allotment.application2 = 0;
- }
- ++i;
+ } else { // Otherwise this is a regular dns response
+ for (int i = 0; i < valid_records; ++i) {
+ HostDBInfo &item = rr_data->info[i];
+ memset(&item, 0, sizeof(item));
+ ip_addr_set(item.ip(), af, e->ent.h_addr_list[i]);
+ item.round_robin = 0;
--- End diff --
Well, first off-- although this is in the diff, that is actually what it is
today.
From looking at it the field is actually `unsigned int round_robin : 1;` so
technically it is an int ;)
> Hostdb consistency problems due to MultiCache
> ---------------------------------------------
>
> Key: TS-4331
> URL: https://issues.apache.org/jira/browse/TS-4331
> Project: Traffic Server
> Issue Type: Bug
> Components: HostDB
> Reporter: Thomas Jackson
> Assignee: Thomas Jackson
> Fix For: 7.0.0
>
>
> This ticket is for the correct long term fix to TS-4207
> pulled from a comment, which wraps up the issue
> {quote}
> Leif Hedstrom I have spent a decent amount of time on this while I was OOO on
> vacation the last couple of weeks. It seems that the root cause of this issue
> has always existed, and that the addition of always doing hostname storing
> (https://github.com/apache/trafficserver/commit/0e703e1e) we are just causing
> the issue to happen all the time.
> To understand the issue I'll give a little background in how hostdb is
> currently working. Basically hostdb is just a wrapper around this templated
> struct called MultiCache. MultiCache is "multi" not because it is templated,
> but because it has two types of storage (static-- blocks and dynamic--
> alloc). The static side of the cache can hold N HostDBInfo structs (the
> results of DNS queries). The dynamic side is used to store the round robin
> records and various strings associated with the record. The size of this
> dynamic space is defined as (N x [estimated_heap_bytes_per_entry. The basic
> problem we are running into is that we are putting too much preassure on the
> dynamic heap-- such that the heap is getting re-used while people still have
> references to items in that space.
> So, I've actually been working on re-writing MultiCache to allocate the
> entire required block at once (so we don't have this problem where the parent
> exists but not the children), but I'm not certain if we want such a change to
> go into the 6.x branch (I'm willing to discuss if we want). If we aren't
> comfortable with such a large change I suggest just accounting for the
> hostname size in the estimated_heap_bytes_per_entry as a stopgap solution.
> The maximum allowable size is 253 (so 254 with null terminator), but we could
> pick a smaller number (~120 or so seems to be more reasonable). Alternatively
> you can increase the number of records in hostdb (and the size accordingly)
> to increase the dynamic heap size.
> TLDR; almost done with the long term solution, but I'm not sure if we want to
> merge that into 6.x-- alternatively we can do a simple workaround in 6.x
> (https://github.com/apache/trafficserver/pull/553)
> {quote}
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