94 lines
3.4 KiB
Markdown
94 lines
3.4 KiB
Markdown
# Clixon datastore
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The Clixon datastore is a stand-alone XML based datastore. The idea is
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to be able to use different datastores backends with the same
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API. There is currently a key-value plugin based on qdbm and a plain
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text-file datastore.
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The datastore is primarily designed to be used by Clixon but can be used
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separately.
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A datastore is a dynamic plugin that is loaded at runtime with a
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well-defined API. This means it is possible to create your own
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datastore and plug it in a Clixon backend at runtime.
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### The functional API
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```
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int xmldb_plugin_load(clicon_handle h, char *filename);
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int xmldb_plugin_unload(clicon_handle h);
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int xmldb_connect(clicon_handle h);
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int xmldb_disconnect(clicon_handle h);
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int xmldb_getopt(clicon_handle h, char *optname, void **value);
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int xmldb_setopt(clicon_handle h, char *optname, void *value);
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int xmldb_get(clicon_handle h, char *db, char *xpath,
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cxobj **xtop, cxobj ***xvec, size_t *xlen);
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int xmldb_put(clicon_handle h, char *db, enum operation_type op,
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char *api_path, cxobj *xt);
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int xmldb_copy(clicon_handle h, char *from, char *to);
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int xmldb_lock(clicon_handle h, char *db, int pid);
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int xmldb_unlock(clicon_handle h, char *db);
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int xmldb_unlock_all(clicon_handle h, int pid);
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int xmldb_islocked(clicon_handle h, char *db);
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int xmldb_exists(clicon_handle h, char *db);
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int xmldb_delete(clicon_handle h, char *db);
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int xmldb_create(clicon_handle h, char *db);
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```
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### Using the API
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To use the API, a client needs the following:
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- A clicon handle.
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- A datastore plugin, such as a text.so or keyvalue.so. These are normally built and installed at Clixon make.
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- A directory where to store databases
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- A yang specification. This needs to be parsed using the Clixon yang_parse() method.
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A client calling the API needs to:
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1. Load a plugin and
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2. Connect to a datastore.
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You can connect to several datastores, even concurrently,
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but in practice in Clixon, you connect to a single store.
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After connecting to a datastore, you can create and modify databases
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within the datastore, and set and get options of the datastore itself.
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When done, you disconnect from the datastore and unload the plugin.
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Within a datastore, the following four databases may exist:
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- running
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- candidate
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- startup
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- tmp
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Initially, a database does not exist but is created by
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xmldb_create(). It is deleted by xmldb_delete(). You may check for
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existence with xmldb_exists(). You need to create a database before
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you can perform any data access on it.
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You may lock a database for exclusive modification according to
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Netconf semantics. You may also unlock a single dabase, unlock all frm
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a specific session.
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You can read a database with xmldb_get() and modify a database with
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xmldb_put(), and xmldb_copy().
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A typical datastore session can be as follows, see the source code of
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[datastore_client.c](datastore_client.c) for a more elaborate example.
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```
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h = clicon_handle_init();
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xmldb_plugin_load(h, plugin);
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xmldb_connect(h);
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xmldb_setopt(h, "dbdir", dbdir);
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xmldb_setopt(h, "yangspec", yspec);
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/* From here databases in the datastore may be accessed */
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xmldb_create(h, "candidate");
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xmldb_copy(h, "running", "candidate");
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xmldb_lock(h, "candidate", 7878);
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xmldb_put(h, "candidate", OP_CREATE, "/interfaces/interface=eth0", xml);
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xmldb_unlock(h, "candidate");
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xmldb_get(h, "candidate", "/", &xml, &xvec, &xlen);
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xmldb_disconnect(h)
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xmdlb_plugin_unload(h);
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```
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