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Niceify the readonlyrecord API. Dont force clients to be exposed to the featch_with_header function

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We dont strictly need to force clients to use CTDB_FETCH_WITH_HEADER instead of CTDB_FETCH when they ask for readonly records.
Have ctdbd internally remap this internally to FETCH_WITH_HEADER and map the reply back to CTDB_FETCH_FUNC or CTDB_FETCH_WITH_HEADER_FUNC based on what the client initially asked for.

This removes the need for the client to know about the CTDB_FETCH_WITH_HEADER_FUNC function and simplifies the client code.
Clients that do not care what the header after the request is can just continue using the old CTDB_FETCH_FUNC call and ctdbd will do all the difficult stuff.

(This used to be ctdb commit 444a7bac4e9a854b06c1ad4cb36c2b58a72001fa)
This commit is contained in:
Ronnie Sahlberg 2012-01-31 17:20:35 +11:00
parent f6c22fe485
commit 65e1e1d3ef
3 changed files with 47 additions and 8 deletions
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7
ctdb/doc/readonlyrecords.txt
View File

@ -89,7 +89,10 @@ This new database is used for tracking delegations for the records. A record in
This tracking database is lockless, using TDB_NOLOCK, and is only ever accessed by the main ctdbd daemon.
The lockless nature and the fact that no other process ever access this TDB means we are guranteed non-blocking access to records in the trcking database.
The ctdb_call PDU is allocated with two new flags WANT_READONLY and WITH_HEADER.
The ctdb_call PDU is allocated with a new flags WANT_READONLY and possibly also a new callid: CTDB_FETCH_WITH_HEADER_FUNC.
This new function returns not only the record, as CTDB_FETCH_FUNC does, but also returns the HEADER prepended to the record.
This function is optional, clients that do not care what the header is can continue using just CTDB_FETCH_FUNC
This first flag is used to explicitely requesting a read-only record from the DMASTER/LMASTER.
The second flag is used to request that the fetch operation will return not only the data for the record but also
the record header.
@ -137,7 +140,7 @@ This will change to instead do
goto finished
else
unlock record
ask ctdb for read-only copy (WANT_READONLY|WITH_HEADER)
ask ctdb for read-only copy (WANT_READONLY[|WITH_HEADER])
if failed to get read-only copy (*A)
ask ctdb to migrate the record onto the node
goto try_again

8
ctdb/libctdb/ctdb.c
View File

@ -832,13 +832,13 @@ static void readrecordlock_retry(struct ctdb_connection *ctdb,
struct ctdb_reply_call *reply;
TDB_DATA data;
/* OK, we've received reply to fetch-with-header migration */
reply = unpack_reply_call(req, CTDB_FETCH_WITH_HEADER_FUNC);
/* OK, we've received reply to fetch migration */
reply = unpack_reply_call(req, CTDB_FETCH_FUNC);
if (!reply || reply->status != 0) {
if (reply) {
DEBUG(ctdb, LOG_ERR,
"ctdb_readrecordlock_async(async):"
" FETCH_WITH_HEADER_FUNC returned %i", reply->status);
" FETCH returned %i", reply->status);
}
lock->callback(lock->ctdb_db, NULL, tdb_null, private);
ctdb_request_free(req); /* Also frees lock. */
@ -920,7 +920,7 @@ ctdb_readrecordlock_internal(struct ctdb_db *ctdb_db, TDB_DATA key,
req->hdr.call->flags = CTDB_IMMEDIATE_MIGRATION;
}
req->hdr.call->db_id = ctdb_db->id;
req->hdr.call->callid = CTDB_FETCH_WITH_HEADER_FUNC;
req->hdr.call->callid = CTDB_FETCH_FUNC;
req->hdr.call->hopcount = 0;
req->hdr.call->keylen = key.dsize;
req->hdr.call->calldatalen = 0;

40
ctdb/server/ctdb_daemon.c
View File

@ -311,6 +311,10 @@ struct daemon_call_state {
uint32_t reqid;
struct ctdb_call *call;
struct timeval start_time;
/* readonly request ? */
uint32_t readonly_fetch;
uint32_t client_callid;
};
/*
@ -339,6 +343,16 @@ static void daemon_call_from_client_callback(struct ctdb_call_state *state)
}
length = offsetof(struct ctdb_reply_call, data) + dstate->call->reply_data.dsize;
/* If the client asked for readonly FETCH, we remapped this to
FETCH_WITH_HEADER when calling the daemon. So we must
strip the extra header off the reply data before passing
it back to the client.
*/
if (dstate->readonly_fetch
&& dstate->client_callid == CTDB_FETCH_FUNC) {
length -= sizeof(struct ctdb_ltdb_header);
}
r = ctdbd_allocate_pkt(client->ctdb, dstate, CTDB_REPLY_CALL,
length, struct ctdb_reply_call);
if (r == NULL) {
@ -348,9 +362,19 @@ static void daemon_call_from_client_callback(struct ctdb_call_state *state)
return;
}
r->hdr.reqid = dstate->reqid;
r->datalen = dstate->call->reply_data.dsize;
r->status = dstate->call->status;
memcpy(&r->data[0], dstate->call->reply_data.dptr, r->datalen);
if (dstate->readonly_fetch
&& dstate->client_callid == CTDB_FETCH_FUNC) {
/* client only asked for a FETCH so we must strip off
the extra ctdb_ltdb header
*/
r->datalen = dstate->call->reply_data.dsize - sizeof(struct ctdb_ltdb_header);
memcpy(&r->data[0], dstate->call->reply_data.dptr + sizeof(struct ctdb_ltdb_header), r->datalen);
} else {
r->datalen = dstate->call->reply_data.dsize;
memcpy(&r->data[0], dstate->call->reply_data.dptr, r->datalen);
}
res = daemon_queue_send(client, &r->hdr);
if (res == -1) {
@ -738,12 +762,24 @@ static void daemon_request_call_from_client(struct ctdb_client *client,
return;
}
dstate->readonly_fetch = 0;
call->call_id = c->callid;
call->key = key;
call->call_data.dptr = c->data + c->keylen;
call->call_data.dsize = c->calldatalen;
call->flags = c->flags;
if (c->flags & CTDB_WANT_READONLY) {
/* client wants readonly record, so translate this into a
fetch with header. remember what the client asked for
so we can remap the reply back to the proper format for
the client in the reply
*/
dstate->client_callid = call->call_id;
call->call_id = CTDB_FETCH_WITH_HEADER_FUNC;
dstate->readonly_fetch = 1;
}
if (header.dmaster == ctdb->pnn) {
state = ctdb_call_local_send(ctdb_db, call, &header, &data);
} else {