virt plugin: Support for multiple read callbacks

Add support to register more than one read callbacks in the
reader thread pool.
The default configuration is to use just one read callback,
for backward compatibility. No user-visible changes are expected
in this scenario.

Signed-off-by: Francesco Romani <fromani@redhat.com>

diff --git a/src/collectd.conf.in b/src/collectd.conf.in
index e5b9643..8c1b10d 100644 (file)
--- a/src/collectd.conf.in
+++ b/src/collectd.conf.in
@@ -1441,6 +1441,7 @@
 #      HostnameFormat name
 #      InterfaceFormat name
 #      PluginInstanceFormat name
+#      Instances 1
 #</Plugin>
 
 #<Plugin vmem>

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 27c4e16..597bbe8 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -7973,6 +7973,12 @@ You can also specify combinations of the B<name> and B<uuid> fields.
 For example B<name uuid> means to concatenate the guest name and UUID
 (with a literal colon character between, thus I<"foo:1234-1234-1234-1234">).
 
+=item B<Instances> B<integer>
+
+How many read instances you want to use for this plugin. The default is one,
+and the sensible setting is a multiple of the B<ReadThreads> value.
+If you are not sure, just use the default setting.
+
 =back
 
 =head2 Plugin C<vmem>

diff --git a/src/virt.c b/src/virt.c
index 2744db0..ae5a247 100644 (file)
--- a/src/virt.c
+++ b/src/virt.c
@@ -52,6 +52,8 @@ static const char *config_keys[] = {"Connection",
 
                                     "PluginInstanceFormat",
 
+                                    "Instances",
+
                                     NULL};
 #define NR_CONFIG_KEYS ((sizeof config_keys / sizeof config_keys[0]) - 1)
 
@@ -99,10 +101,6 @@ struct lv_read_state {
   int nr_interface_devices;
 };
 
-static struct lv_read_state read_state = {
-    NULL, 0, NULL, 0, NULL, 0,
-};
-
 static void free_domains(struct lv_read_state *state);
 static int add_domain(struct lv_read_state *state, virDomainPtr dom);
 
@@ -115,6 +113,23 @@ static int add_interface_device(struct lv_read_state *state, virDomainPtr dom,
                                 const char *path, const char *address,
                                 unsigned int number);
 
+#define PARTITION_TAG_MAX_LEN 32
+struct lv_read_instance {
+  struct lv_read_state read_state;
+  char tag[PARTITION_TAG_MAX_LEN];
+  size_t id;
+};
+
+struct lv_user_data {
+  struct lv_read_instance inst;
+  user_data_t ud;
+};
+
+#define NR_INSTANCES_DEFAULT 1
+#define NR_INSTANCES_MAX 128
+static size_t nr_instances = NR_INSTANCES_DEFAULT;
+static struct lv_user_data lv_read_user_data[NR_INSTANCES_MAX];
+
 /* HostnameFormat. */
 #define HF_MAX_FIELDS 3
 
@@ -284,13 +299,6 @@ static void submit_derive2(const char *type, derive_t v0, derive_t v1,
   submit(dom, type, devname, values, STATIC_ARRAY_SIZE(values));
 } /* void submit_derive2 */
 
-static int lv_init(void) {
-  if (virInitialize() != 0)
-    return -1;
-  else
-    return 0;
-}
-
 static int lv_config(const char *key, const char *value) {
   if (virInitialize() != 0)
     return 1;
@@ -461,15 +469,39 @@ static int lv_config(const char *key, const char *value) {
     return 0;
   }
 
+  if (strcasecmp(key, "Instances") == 0) {
+    char *eptr = NULL;
+    long val = strtol(value, &eptr, 10);
+    if (eptr == NULL || *eptr != '\0')
+      return 1;
+    if (val <= 0) {
+      ERROR(PLUGIN_NAME " plugin: Instances <= 0 makes no sense.");
+      return 1;
+    }
+    if (val > NR_INSTANCES_MAX) {
+      ERROR(PLUGIN_NAME " plugin: Instances=%li > NR_INSTANCES_MAX=%i"
+                        " use a lower setting or recompile the plugin.",
+            val, NR_INSTANCES_MAX);
+      return 1;
+    }
+    nr_instances = (size_t)val;
+    return 0;
+  }
+
   /* Unrecognised option. */
   return -1;
 }
 
-static int lv_read(void) {
+static int lv_read(user_data_t *ud) {
   time_t t;
-  struct lv_read_state *state = &read_state;
+  struct lv_read_instance *inst = ud->data;
+  struct lv_read_state *state = &inst->read_state;
+  if (!inst) {
+    ERROR(PLUGIN_NAME " plugin: NULL userdata");
+    return -1;
+  }
 
-  if (conn == NULL) {
+  if (inst->id == 0 && conn == NULL) {
     /* `conn_string == NULL' is acceptable. */
     conn = virConnectOpenReadOnly(conn_string);
     if (conn == NULL) {
@@ -649,6 +681,33 @@ static int lv_read(void) {
   return 0;
 }
 
+static int lv_init_instance(size_t i, plugin_read_cb callback) {
+  struct lv_user_data *lv_ud = &(lv_read_user_data[i]);
+  struct lv_read_instance *inst = &lv_ud->inst;
+
+  memset(lv_ud, 0, sizeof(*lv_ud));
+
+  ssnprintf(inst->tag, sizeof(inst->tag), "%s-%zu", PLUGIN_NAME, i);
+  inst->id = i;
+
+  user_data_t *ud = &lv_ud->ud;
+  ud->data = inst;
+  ud->free_func = NULL;
+
+  INFO(PLUGIN_NAME "plugin: reader %s initialized", inst->tag);
+  return plugin_register_complex_read(NULL, inst->tag, callback, 0, ud);
+}
+
+static int lv_init(void) {
+  if (virInitialize() != 0)
+    return -1;
+
+  for (size_t i = 0; i < nr_instances; ++i)
+    lv_init_instance(i, lv_read);
+
+  return 0;
+}
+
 static int refresh_lists(struct lv_read_state *state) {
   int n;
 
@@ -959,10 +1018,12 @@ static int ignore_device_match(ignorelist_t *il, const char *domname,
 }
 
 static int lv_shutdown(void) {
-  struct lv_read_state *state = &read_state;
-  free_block_devices(state);
-  free_interface_devices(state);
-  free_domains(state);
+  for (size_t i = 0; i < nr_instances; ++i) {
+    struct lv_read_state *state = &(lv_read_user_data[i].inst.read_state);
+    free_block_devices(state);
+    free_interface_devices(state);
+    free_domains(state);
+  }
 
   if (conn != NULL)
     virConnectClose(conn);
@@ -981,7 +1042,7 @@ static int lv_shutdown(void) {
 void module_register(void) {
   plugin_register_config(PLUGIN_NAME, lv_config, config_keys, NR_CONFIG_KEYS);
   plugin_register_init(PLUGIN_NAME, lv_init);
-  plugin_register_read(PLUGIN_NAME, lv_read);
+  plugin_register_complex_read(NULL, PLUGIN_NAME, lv_read, 0, NULL);
   plugin_register_shutdown(PLUGIN_NAME, lv_shutdown);
 }