Hi, everyone.
In ReplicatedPG::_write_copy_chunk method, I saw the following code:
if (!cop->temp_cursor.attr_complete) {
t->touch(cop->results.temp_oid);
for (map<string, bufferlist>::iterator p = cop->attrs.begin();
p != cop->attrs.end(); ++p) {
cop->results.attrs[string("_") + p->first] = p->second;
t->setattr(cop->results.temp_oid, string("_") + p->first,
p->second);
}
cop->attrs.clear();
}
It seems that user specified attrs are prefixed by "_", but why add
"_" here, in ReplicatedPG::_write_copy_chunk? It seems that this
method is used for copying objects in the RADOS cluster,.
On 23 August 2017 at 15:40, Xuehan Xu <xxhdx1985126@xxxxxxxxx> wrote:
> It seems that when calling ReplicatedPG::getattrs_maybe_cache in
> ReplicatedPG::fill_in_copy_get, "user_only" should be false. Is this
> right?
>
> On 23 August 2017 at 15:25, Xuehan Xu <xxhdx1985126@xxxxxxxxx> wrote:
>> I submitted an issue for this:
>> http://tracker.ceph.com/issues/21072?next_issue_id=21071
>>
>> On 23 August 2017 at 15:24, Xuehan Xu <xxhdx1985126@xxxxxxxxx> wrote:
>>> Hi, everyone.
>>>
>>> Recently, we did a test as follows:
>>>
>>> We enabled cache tier and added a cache pool "vms_back_cache" on top
>>> of the base pool "vms_back". we first created an object, and then
>>> created a snap in the base pool and writing to that object again,
>>> which would make the object be promoted into the cache pool. At this
>>> time, we used "ceph-objectstore-tool" to dump the object, and the
>>> result is as follows:
>>>
>>> {
>>> "id": {
>>> "oid": "test.obj.6",
>>> "key": "",
>>> "snapid": -2,
>>> "hash": 750422257,
>>> "max": 0,
>>> "pool": 11,
>>> "namespace": "",
>>> "max": 0
>>> },
>>> "info": {
>>> "oid": {
>>> "oid": "test.obj.6",
>>> "key": "",
>>> "snapid": -2,
>>> "hash": 750422257,
>>> "max": 0,
>>> "pool": 11,
>>> "namespace": ""
>>> },
>>> "version": "5010'5",
>>> "prior_version": "4991'3",
>>> "last_reqid": "client.175338.0:1",
>>> "user_version": 5,
>>> "size": 4194303,
>>> "mtime": "2017-08-23 15:09:03.459892",
>>> "local_mtime": "2017-08-23 15:09:03.461111",
>>> "lost": 0,
>>> "flags": 4,
>>> "snaps": [],
>>> "truncate_seq": 0,
>>> "truncate_size": 0,
>>> "data_digest": 4294967295,
>>> "omap_digest": 4294967295,
>>> "watchers": {}
>>> },
>>> "stat": {
>>> "size": 4194303,
>>> "blksize": 4096,
>>> "blocks": 8200,
>>> "nlink": 1
>>> },
>>> "SnapSet": {
>>> "snap_context": {
>>> "seq": 13,
>>> "snaps": [
>>> 13
>>> ]
>>> },
>>> "head_exists": 1,
>>> "clones": [
>>> {
>>> "snap": 13,
>>> "size": 4194303,
>>> "overlap": "[0~100,115~4194188]"
>>> }
>>> ]
>>> }
>>> }
>>>
>>> Then we did cache-flush and cache-evict to flush that object down to
>>> the base pool, and, again, used "ceph-objectstore-tool" to dump the
>>> object in the base pool:
>>>
>>> {
>>> "id": {
>>> "oid": "test.obj.6",
>>> "key": "",
>>> "snapid": -2,
>>> "hash": 750422257,
>>> "max": 0,
>>> "pool": 10,
>>> "namespace": "",
>>> "max": 0
>>> },
>>> "info": {
>>> "oid": {
>>> "oid": "test.obj.6",
>>> "key": "",
>>> "snapid": -2,
>>> "hash": 750422257,
>>> "max": 0,
>>> "pool": 10,
>>> "namespace": ""
>>> },
>>> "version": "5015'4",
>>> "prior_version": "4991'2",
>>> "last_reqid": "osd.34.5013:1",
>>> "user_version": 5,
>>> "size": 4194303,
>>> "mtime": "2017-08-23 15:09:03.459892",
>>> "local_mtime": "2017-08-23 15:10:48.122138",
>>> "lost": 0,
>>> "flags": 52,
>>> "snaps": [],
>>> "truncate_seq": 0,
>>> "truncate_size": 0,
>>> "data_digest": 163942140,
>>> "omap_digest": 4294967295,
>>> "watchers": {}
>>> },
>>> "stat": {
>>> "size": 4194303,
>>> "blksize": 4096,
>>> "blocks": 8200,
>>> "nlink": 1
>>> },
>>> "SnapSet": {
>>> "snap_context": {
>>> "seq": 13,
>>> "snaps": [
>>> 13
>>> ]
>>> },
>>> "head_exists": 1,
>>> "clones": [
>>> {
>>> "snap": 13,
>>> "size": 4194303,
>>> "overlap": "[]"
>>> }
>>> ]
>>> }
>>> }
>>>
>>> As is shown, the "overlap" field is empty.
>>> In the osd log, we found the following records:
>>>
>>> 2017-08-23 12:46:36.083014 7f675c704700 20 osd.0 pg_epoch: 19 pg[3.3(
>>> v 15'2 (0'0,15'2] local-les=15 n=2 ec=14 les/c/f 15/15/0 14/14/14)
>>> [0,2,1] r=0 lpr=14 crt=0'0 lcod 15'1 mlcod 15'1 active+clean] got
>>> attrs
>>> 2017-08-23 12:46:36.083021 7f675c704700 15
>>> filestore(/home/xuxuehan/github-xxh-fork/ceph/src/dev/osd0) read
>>> 3.3_head/#3:dd4db749:test-rados-api-xxh02v.ops.corp.qihoo.net-10886-3::foo:head#
>>> 0~8
>>> 2017-08-23 12:46:36.083398 7f675c704700 10
>>> filestore(/home/xuxuehan/github-xxh-fork/ceph/src/dev/osd0)
>>> FileStore::read
>>> 3.3_head/#3:dd4db749:test-rados-api-xxh02v.ops.corp.qihoo.net-10886-3::foo:head#
>>> 0~8/8
>>> 2017-08-23 12:46:36.083414 7f675c704700 20 osd.0 pg_epoch: 19 pg[3.3(
>>> v 15'2 (0'0,15'2] local-les=15 n=2 ec=14 les/c/f 15/15/0 14/14/14)
>>> [0,2,1] r=0 lpr=14 crt=0'0 lcod 15'1 mlcod 15'1 active+clean] got
>>> data
>>> 2017-08-23 12:46:36.083444 7f675c704700 20 osd.0 pg_epoch: 19 pg[3.3(
>>> v 15'2 (0'0,15'2] local-les=15 n=2 ec=14 les/c/f 15/15/0 14/14/14)
>>> [0,2,1] r=0 lpr=14 crt=0'0 lcod 15'1 mlcod 15'1 active+clean]
>>> cursor.is_complete=0 0 attrs 8 bytes 0 omap header bytes 0 omap data
>>> bytes in 0 keys 0 reqids
>>> 2017-08-23 12:46:36.083457 7f675c704700 10 osd.0 pg_epoch: 19 pg[3.3(
>>> v 15'2 (0'0,15'2] local-les=15 n=2 ec=14 les/c/f 15/15/0 14/14/14)
>>> [0,2,1] r=0 lpr=14 crt=0'0 lcod 15'1 mlcod 15'1 active+clean]
>>> dropping ondisk_read_lock
>>> 2017-08-23 12:46:36.083467 7f675c704700 15 osd.0 pg_epoch: 19 pg[3.3(
>>> v 15'2 (0'0,15'2] local-les=15 n=2 ec=14 les/c/f 15/15/0 14/14/14)
>>> [0,2,1] r=0 lpr=14 crt=0'0 lcod 15'1 mlcod 15'1 active+clean]
>>> do_osd_op_effects osd.0 con 0x7f67874f0d00
>>> 2017-08-23 12:46:36.083478 7f675c704700 15 osd.0 pg_epoch: 19 pg[3.3(
>>> v 15'2 (0'0,15'2] local-les=15 n=2 ec=14 les/c/f 15/15/0 14/14/14)
>>> [0,2,1] r=0 lpr=14 crt=0'0 lcod 15'1 mlcod 15'1 active+clean]
>>> log_op_stats osd_op(osd.0.6:2 3.92edb2bb
>>> test-rados-api-xxh02v.ops.corp
>>>
>>> It seems that, when doing "copy-get", no extensive attributes are
>>> copied. We believe that it's the following code that led to this
>>> result:
>>>
>>> int ReplicatedPG::getattrs_maybe_cache(ObjectContextRef obc,
>>> map<string, bufferlist> *out,
>>> bool user_only) {
>>> int r = 0;
>>> if (pool.info.require_rollback()) {
>>> if (out)
>>> *out = obc->attr_cache;
>>> } else {
>>> r = pgbackend->objects_get_attrs(obc->obs.oi.soid, out);
>>> }
>>> if (out && user_only) {
>>> map<string, bufferlist> tmp;
>>> for (map<string, bufferlist>::iterator i = out->begin();
>>> i != out->end(); ++i) {
>>> if (i->first.size() > 1 && i->first[0] == '_')
>>> tmp[i->first.substr(1, i->first.size())].claim(i->second);
>>> }
>>> tmp.swap(*out);
>>> }
>>> return r;
>>> }
>>>
>>> It seems that when "user_only" is true, extensive attributes without a
>>> '_' as the starting character in its name would be filtered out. Is it
>>> supposed to be doing things in this way?
>>> And we found that there are only two places in the source code that
>>> invoked ReplicatedPG::getattrs_maybe_cache, in both of which
>>> "user_only" is true. Why add this parameter?
>>>
>>> By the way, we also found that these codes are added in commit
>>> 78d9c0072bfde30917aea4820a811d7fc9f10522, but we don't understand the
>>> purpose of it.
>>>
>>> Thank you:-)
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