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List pagination locking for state-data changes

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Changed semantics of locking: instead of relying of locking running-db,
an automatic lock bound to a session is maintained. When the session closes
the lock is released.
This commit is contained in:
Olof hagsand 2021-10-28 14:49:33 +02:00
parent 197fc16e69
commit eea6d549f6
5 changed files with 25 additions and 19 deletions
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13
apps/backend/backend_get.c
View file

@ -592,11 +592,16 @@ get_list_pagination(clicon_handle h,
#endif
}
else {/* Check if running locked (by this session) */
if ((iddb = xmldb_islocked(h, "running")) != 0 &&
iddb == ce->ce_id)
if ((iddb = xmldb_islocked(h, PAGINATE_STATE_LOCK)) != 0){
if (iddb == ce->ce_id)
locked = 1;
else
locked = 0;
}
else {
xmldb_lock(h, PAGINATE_STATE_LOCK, ce->ce_id);
locked = 1;
else
locked = 0;
}
if ((ret = clixon_pagination_cb_call(h, xpath, locked,
offset, limit,
xret)) < 0)

5
apps/backend/clixon_backend_plugin.h
View file

@ -38,6 +38,11 @@
#ifndef _CLIXON_BACKEND_PLUGIN_H_
#define _CLIXON_BACKEND_PLUGIN_H_
/*
* Constants
*/
#define PAGINATE_STATE_LOCK "paginate-state-lock"
/*
* Types
*/

17
apps/backend/clixon_backend_transaction.c
View file

@ -309,15 +309,16 @@ pagination_limit(pagination_data pd)
return ((pagination_data_t *)pd)->pd_limit;
}
/*! Get pagination data: locked parameter
/*! Get pagination data: locked parameter for state data
*
* Pagination can use a lock/transaction mechanism
* If locking is not used, the plugin cannot expect more pagination calls, and no state or
* caching should be used
* If locking is used, the pagination is part of a session transaction and the plugin may cache
* state (such as a cache) and can expect more pagination calls until the running db-lock is
* released, (see ca_lockdb)
* The transaction is the regular lock/unlock db of running-db of a specific session.
* A "paginate" lock is set for a specific session when list-pagination is in progress.
* If locking is set, the pagination is part of a session transaction and the plugin may
* cache state (such as a cache) and can expect more pagination calls until the "paginate"
* db-lock is released.
*
* If you want to do the same for config data, it is recommended to use lock-db on
* the appropriate database, but this risks of indefinite blocking, as long as the
* session endures.
* @param[in] pd Pagination userdata
* @retval locked 0: unlocked/stateless 1: locked by this caller
*/

6
apps/cli/cli_show.c
View file

@ -919,7 +919,6 @@ cli_pagination(clicon_handle h,
uint32_t limit = 0;
cxobj **xvec = NULL;
size_t xlen;
int locked = 0;
if (cvec_len(argv) != 5){
clicon_err(OE_PLUGIN, 0, "Expected usage: <xpath> <prefix> <namespace> <format> <limit>");
@ -949,9 +948,6 @@ cli_pagination(clicon_handle h,
}
if ((nsc = xml_nsctx_init(prefix, namespace)) == NULL)
goto done;
if (clicon_rpc_lock(h, "running") < 0)
goto done;
locked++;
for (i = 0;; i++){
if (clicon_rpc_get_pageable_list(h, "running", xpath, nsc,
CONTENT_ALL,
@ -1004,8 +1000,6 @@ cli_pagination(clicon_handle h,
} /* for i */
retval = 0;
done:
if (locked)
clicon_rpc_unlock(h, "running");
if (xvec)
free(xvec);
if (xret)

3
example/main/example_backend.c
View file

@ -545,6 +545,7 @@ example_statefile(clicon_handle h,
* @param[in] xpath Registered XPath using canonical prefixes
* @param[in] userargs Per-call user arguments
* @param[in] arg Per-path user argument
* @see example_lockdb
*/
int
example_pagination(void *h0,
@ -667,7 +668,7 @@ example_lockdb(clicon_handle h,
/* Part of cached pagination example
*/
if (strcmp(db, "running") == 0 && lock == 0 &&
if (strcmp(db, PAGINATE_STATE_LOCK) == 0 && lock == 0 &&
_state && _state_file && _state_file_cached && _state_file_transaction){
if (_state_xml_cache){
xml_free(_state_xml_cache);