plugin: Add a new type of timeseries-fetcher plugins.

The new type (soon to replace the old) bundles a DESCRIBE callback along with
the actual fetch callback. DESCRIBE can be used to retrieve information about
a timeseries.

diff --git a/src/core/plugin.c b/src/core/plugin.c
index 44ea48a06b53e38434cd23a6a9a951d689d48cf2..8d836cc981de718a9f42cb270ec1b7f8ce66d783 100644 (file)
--- a/src/core/plugin.c
+++ b/src/core/plugin.c
@@ -114,6 +114,14 @@ typedef struct {
 } reader_t;
 #define READER(obj) ((reader_t *)(obj))
 
+typedef struct {
+       callback_t super; /* cb_callback will always be NULL */
+#define ts_user_data super.cb_user_data
+#define ts_ctx super.cb_ctx
+       sdb_timeseries_fetcher_t impl;
+} ts_fetcher_t;
+#define TS_FETCHER(obj) ((ts_fetcher_t *)(obj))
+
 /*
  * private variables
  */
@@ -134,6 +142,7 @@ static sdb_llist_t      *cname_list = NULL;
 static sdb_llist_t      *shutdown_list = NULL;
 static sdb_llist_t      *log_list = NULL;
 static sdb_llist_t      *ts_fetcher_list = NULL;
+static sdb_llist_t      *timeseries_fetcher_list = NULL;
 static sdb_llist_t      *writer_list = NULL;
 static sdb_llist_t      *reader_list = NULL;
 
@@ -148,6 +157,7 @@ static struct {
        { "shutdown",           &shutdown_list },
        { "log",                &log_list },
        { "timeseries fetcher", &ts_fetcher_list },
+       { "timeseries fetcher", &timeseries_fetcher_list },
        { "store writer",       &writer_list },
        { "store reader",       &reader_list },
 };
@@ -505,6 +515,52 @@ static sdb_type_t reader_type = {
        plugin_reader_destroy
 };
 
+static int
+plugin_ts_fetcher_init(sdb_object_t *obj, va_list ap)
+{
+       sdb_timeseries_fetcher_t *impl;
+       sdb_object_t *ud;
+
+       if (! plugin_init_ok(obj, ap))
+               return -1;
+
+       impl = va_arg(ap, sdb_timeseries_fetcher_t *);
+       ud = va_arg(ap, sdb_object_t *);
+       assert(impl);
+
+       if ((! impl->describe) || (! impl->fetch)) {
+               sdb_log(SDB_LOG_ERR, "core: timeseries fetcher callback '%s' "
+                               "does not fully implement the interface.",
+                               obj->name);
+               return -1;
+       }
+
+       /* ctx may be NULL if the callback was not registered by a plugin */
+
+       TS_FETCHER(obj)->impl = *impl;
+       TS_FETCHER(obj)->ts_ctx  = ctx_get();
+       sdb_object_ref(SDB_OBJ(TS_FETCHER(obj)->ts_ctx));
+
+       sdb_object_ref(ud);
+       TS_FETCHER(obj)->ts_user_data = ud;
+       return 0;
+} /* plugin_ts_fetcher_init */
+
+static void
+plugin_ts_fetcher_destroy(sdb_object_t *obj)
+{
+       assert(obj);
+       sdb_object_deref(TS_FETCHER(obj)->ts_user_data);
+       sdb_object_deref(SDB_OBJ(TS_FETCHER(obj)->ts_ctx));
+} /* plugin_ts_fetcher_destroy */
+
+static sdb_type_t ts_fetcher_type = {
+       sizeof(ts_fetcher_t),
+
+       plugin_ts_fetcher_init,
+       plugin_ts_fetcher_destroy
+};
+
 static int
 module_init(const char *name, lt_dlhandle lh, sdb_plugin_info_t *info)
 {
@@ -1020,6 +1076,14 @@ sdb_plugin_register_ts_fetcher(const char *name,
                        name, callback, user_data);
 } /* sdb_plugin_register_ts_fetcher */
 
+int
+sdb_plugin_register_timeseries_fetcher(const char *name,
+               sdb_timeseries_fetcher_t *fetcher, sdb_object_t *user_data)
+{
+       return plugin_add_impl(&timeseries_fetcher_list, ts_fetcher_type, "time-series fetcher",
+                       name, fetcher, user_data);
+} /* sdb_plugin_register_timeseries_fetcher */
+
 int
 sdb_plugin_register_writer(const char *name,
                sdb_store_writer_t *writer, sdb_object_t *user_data)
@@ -1481,6 +1545,8 @@ sdb_plugin_fetch_timeseries(const char *type, const char *id,
 {
        callback_t *plugin;
        sdb_plugin_fetch_ts_cb callback;
+
+       ts_fetcher_t *fetcher;
        sdb_timeseries_t *ts;
 
        ctx_t *old_ctx;
@@ -1488,6 +1554,15 @@ sdb_plugin_fetch_timeseries(const char *type, const char *id,
        if ((! type) || (! id) || (! opts))
                return NULL;
 
+       fetcher = TS_FETCHER(sdb_llist_search_by_name(timeseries_fetcher_list, type));
+       if (fetcher) {
+               old_ctx = ctx_set(fetcher->ts_ctx);
+               ts = fetcher->impl.fetch(id, opts, fetcher->ts_user_data);
+               ctx_set(old_ctx);
+               return ts;
+       }
+
+       /* fallback code */
        plugin = CB(sdb_llist_search_by_name(ts_fetcher_list, type));
        if (! plugin) {
                sdb_log(SDB_LOG_ERR, "core: Cannot fetch time-series of type %s: "

diff --git a/src/include/core/plugin.h b/src/include/core/plugin.h
index 6c4a2e16cfdf674c2884f560ac158ef7836733d3..5a26c39fb78b10f503667b9060e4d20f01416746 100644 (file)
--- a/src/include/core/plugin.h
+++ b/src/include/core/plugin.h
@@ -240,11 +240,12 @@ sdb_plugin_register_log(const char *name, sdb_plugin_log_cb callback,
                sdb_object_t *user_data);
 
 /*
- * sdb_plugin_register_ts_fetcher:
- * Register a "time-series fetcher" function to be called whenever retrieving
- * a time-series from a data-store. The callback will receive an identifier
- * describing where to retrieve the data from (e.g. a filename or some kind of
- * URL) and options which further describe the query.
+ * sdb_plugin_register_timeseries_fetcher:
+ * Register a "time-series fetcher" to be called whenever retrieving a
+ * time-series from a data-store or information about it. The fetch callback
+ * will receive an identifier describing where to retrieve the data from (e.g.
+ * a filename or some kind of URL) and options which further describe the
+ * query.
  *
  * The name is used literally (without prepending the plugin name) to look up
  * the appropriate fetcher callback.
@@ -258,6 +259,9 @@ sdb_plugin_register_log(const char *name, sdb_plugin_log_cb callback,
 int
 sdb_plugin_register_ts_fetcher(const char *name,
                sdb_plugin_fetch_ts_cb callback, sdb_object_t *user_data);
+int
+sdb_plugin_register_timeseries_fetcher(const char *name,
+               sdb_timeseries_fetcher_t *fetcher, sdb_object_t *user_data);
 
 /*
  * sdb_plugin_register_writer:

diff --git a/src/include/core/timeseries.h b/src/include/core/timeseries.h
index ce4f0d24c974d89f8e7f6af8fa41ac4c5dac4821..3a50dc6c57d269ee05f3b285d09b5a3bb132267a 100644 (file)
--- a/src/include/core/timeseries.h
+++ b/src/include/core/timeseries.h
@@ -29,6 +29,7 @@
 #define SDB_CORE_TIMESERIES_H 1
 
 #include "sysdb.h"
+#include "core/object.h"
 #include "core/time.h"
 #include "utils/strbuf.h"
 
@@ -118,6 +119,27 @@ sdb_timeseries_create(size_t data_names_len, const char * const *data_names,
 void
 sdb_timeseries_destroy(sdb_timeseries_t *ts);
 
+/*
+ * A timeseries fetcher fetches data from a timeseries data-store.
+ */
+typedef struct {
+       /*
+        * describe:
+        * Retrieve information about the timeseries from the data-store. The
+        * returned timeseries info object must be freeable using
+        * sdb_timeseries_info_destroy.
+        */
+       sdb_timeseries_info_t *(*describe)(const char *id, sdb_object_t *user_data);
+
+       /*
+        * fetch:
+        * Read timeseries data from the data-store. The returned timeseries
+        * object must be freeable using sdb_timeseries_destroy.
+        */
+       sdb_timeseries_t *(*fetch)(const char *id,
+                       sdb_timeseries_opts_t *opts, sdb_object_t *user_data);
+} sdb_timeseries_fetcher_t;
+
 /*
  * sdb_timeseries_tojson:
  * Serialize a time-series to JSON written to the specified string buffer.