[Tarantool-patches] [PATCH v2 10/11] box: enrich ER_READONLY with new details
Vladislav Shpilevoy
v.shpilevoy at tarantool.org
Sat Nov 13 02:24:38 MSK 2021
Hi! Thanks for the review!
> 12.11.2021 02:54, Vladislav Shpilevoy пишет:
>> ER_READONLY used not to have any details about the exact reason
>> why the instance is read-only. The patch changes that by adding
>> new fields into the error which explain why the error happened and
>> even help to avoid it for next requests.
>>
>
> Thanks for the changes!
>
> Please, find two comments below.
>
> Sorry for coming up late with this one, but I think it'd be good
> to report ro reason in box.info. Maybe box.info.ro_reason or
> something similar. Only when box.info.ro is true, of course.
>
> Otherwise we help the user only partially. He sees what's wrong when receives
> an error, but has to check every parameter manually when checks box.info.ro
Sounds useful, I added it in a new commit on top of the branch. See a new
email in the same thread.
>> diff --git a/src/box/box.cc b/src/box/box.cc
>> index 1ed1ce3f8..323982969 100644
>> --- a/src/box/box.cc
>> +++ b/src/box/box.cc
>> @@ -177,16 +177,54 @@ box_update_ro_summary(void)
>> static int
>> box_check_writable(void)
>> {
>> - if (is_ro_summary) {
>> + if (!is_ro_summary)
>> + return 0;
>> + struct error *e = diag_set(ClientError, ER_READONLY);
>> + struct raft *raft = box_raft();
>> + /*
>> + * In case of multiple reasons at the same time only one is reported.
>> + * But the order is important. For example, if the instance has election
>> + * enabled, for the client it is better to see that it is a 'follower'
>> + * and who is the leader than just see cfg 'read_only' is true.
>> + */
>> + if (raft_is_ro(raft)) {
>> + error_set_str(e, "reason", "election");
>> + error_set_str(e, "state", raft_state_str(raft->state));
>> + error_set_uint(e, "term", raft->volatile_term);
>> + uint32_t id = raft->leader;
>> + if (id != REPLICA_ID_NIL) {
>> + error_set_uint(e, "leader_id", id);
>> + struct replica *r = replica_by_id(id);
>> + /*
>> + * XXX: when the leader is dropped from _cluster, it
>> + * is not reported to Raft.
>> + */
>> + if (r != NULL)
>> + error_set_uuid(e, "leader_uuid", &r->uuid);
>> + }
>> + } else if (txn_limbo_is_ro(&txn_limbo)) {
>> + error_set_str(e, "reason", "synchro");
>> + uint32_t id = txn_limbo.owner_id;
>> + error_set_uint(e, "queue_owner_id", id);
>> + error_set_uint(e, "term", raft->volatile_term);
>
> I just noticed, we should report txn_limbo_greatest_term here, probably.
>
> This instance (which received ER_READONLY) is the leader, but hasn't claimed
> the limbo yet.
> This only makes sense when limbo term is behind raft's one.
Hmm, you are probably right. Thanks for noticing! Fixed in the
previous commit.
====================
@@ -214,7 +214,7 @@ box_check_writable(void)
} else if (txn_limbo_is_ro(&txn_limbo)) {
error_set_str(e, "reason", "synchro");
uint32_t id = txn_limbo.owner_id;
- uint64_t term = raft->volatile_term;
+ uint64_t term = txn_limbo.promote_greatest_term;
error_set_uint(e, "queue_owner_id", id);
error_set_uint(e, "term", term);
====================
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