Merge pull request #26 from andreasscherman/add-vacuum-metrics

Add mxid and xid metrics

Author: dflemstr

README.md

@@ -217,14 +217,21 @@ Called once per your Postgres cluster.
   per each slave. If the slave and the master are in synchronous state,
   the replication delay is zero.
 
-
-### Database Local Directory Based (Global) Metrics
-
 * **get_stats_wal_file_amount**:
   This graph shows the amount of files in your database clusters WAL log
   directory (pg_wal or pg_xlog). If the WAL file amount starts to suddenly
   increase, you probably have issues with your WAL archiving process, which
   might lead to the disk filling up, and you database cluster crashing.
+  
+* **get_xid_remaining_ratio, get_multixact_remaining_ratio, get_multixact_members_remaining_ratio**:
+  These metric shows the corresponding remaining % of transaction ids ("xid"), multixact ids ("mxid"), 
+  and multixact members that are available for postgres to use before exhaustion. 
+  Useful for ensuring that the vacuuming is working as intended for your postgres instance.
+
+* **get_multixact_members_per_mxid**:
+  This metric emits the number of multixact members there are per multixact ID. A larger number means
+  that it'll be quicker for the multixact members exhaustion to happen (as can 
+  be seen in **get_multixact_members_usage_ratio**). 
 
 
 ## Short Overview of Python Modules

etc/postgresql-metrics/default/postgresql-metrics.yml

@@ -38,8 +38,7 @@ ffwd:
 # Each entry must be a tuple with the function name, and a time interval in seconds
 # to call that metrics function.
 #
-# db_functions: Functions taking DB connection and returning a list of metrics,
-#               called once per each database in cluster.
+# db_functions: Functions called once per each database in cluster.
 db_functions:
     - ["get_stats_disk_usage_for_database", 180]
     - ["get_stats_tx_rate_for_database", 60]
@@ -52,15 +51,14 @@ db_functions:
     # replication status relies on `pg_stat_wal_receiver`, which is only available on postgres 9.6+
     # - ["get_stats_incoming_replication_status", 30]
 
-# global_db_functions: Functions taking DB connection and returning a list of metrics,
-#                      called once per the whole database cluster.
+# global_db_functions: Functions called once per the whole database cluster.
 global_db_functions:
     - ["get_stats_client_connections", 60]
     - ["get_stats_lock_statistics", 60]
     - ["get_stats_heap_hit_statistics", 60]
     - ["get_stats_replication_delays", 60]
-
-# data_dir_functions: Functions taking a file path to Postgres data dir and returning
-#                     a list of metrics, called once per the whole database cluster.
-data_dir_functions:
     - ["get_stats_wal_file_amount", 180]
+    - ["get_multixact_members_per_mxid", 60]
+    - ["get_multixact_members_remaining_ratio", 60]
+    - ["get_multixact_remaining_ratio", 60]
+    - ["get_xid_remaining_ratio", 60]

postgresql_metrics/default_metrics.py

@@ -116,6 +116,29 @@ def metric_sec_since_oldest_xact_start(database_name, value):
                                   'unit': 's'})
 
 
+def metric_xid_remaining_ratio(value):
+    return create_default_metric(value,
+                                 {'what': 'xid-remaining',
+                                  'unit': '%'})
+
+
+def metric_multixact_remaining_ratio(value):
+    return create_default_metric(value,
+                                 {'what': 'mxid-remaining',
+                                  'unit': '%'})
+
+
+def metric_multixact_members_per_mxid(value):
+    return create_default_metric(value,
+                                 {'what': 'multixact-members-per-mxid',
+                                  'unit': 'members/id'})
+
+
+def metric_multixact_members_remaining_ratio(value):
+    return create_default_metric(value,
+                                 {'what': 'multixact-members-remaining',
+                                  'unit': '%'})
+
 def metric_wal_file_amount(value):
     return create_default_metric(value,
                                  {'what': 'wal-file-amount',

postgresql_metrics/localhost_postgres_stats.py

@@ -24,6 +24,18 @@
 LOG = get_logger()
 
 
+def get_multixact_member_files(data_dir):
+    try:
+        members_dir = os.path.join(data_dir, "pg_multixact", "members")
+        if os.path.isdir(members_dir):
+            return len([f for f in os.listdir(members_dir) if os.path.isfile(os.path.join(members_dir, f))])
+        else:
+            LOG.exception(f"Missing pg_multixact/members directory in data_dir: {data_dir}")
+    except OSError:
+        LOG.exception('Failed accessing multixact member files in: {data_dir}. Is data dir readable by user?')
+    return 0
+
+
 def get_amount_of_wal_files(data_dir):
     amount_of_wal_files = 0
     try:

postgresql_metrics/metrics_gatherer.py

@@ -43,9 +43,13 @@
     metric_replication_delay_bytes,
     metric_wal_file_amount,
     metric_incoming_replication_running,
+    metric_multixact_members_per_mxid,
+    metric_multixact_remaining_ratio,
+    metric_xid_remaining_ratio,
+    metric_multixact_members_remaining_ratio,
 )
 
-from postgresql_metrics.localhost_postgres_stats import get_amount_of_wal_files
+from postgresql_metrics.localhost_postgres_stats import get_amount_of_wal_files, get_multixact_member_files
 
 from postgresql_metrics.postgres_queries import (
     get_client_connections_amount,
@@ -60,23 +64,29 @@
     get_replication_delays,
     get_tables_with_oids_for_current_db,
     get_wal_receiver_status,
+    get_max_mxid_age,
+    get_max_xid_age,
 )
 
+MEMBERS_PER_MEMBER_FILE = 52352
+MAX_MULTIXACT_MEMBERS = 2**32
+WRAPAROUND_LIMIT = (2**32/2) - 1
 
 # Notice that all functions here are expected to return a list of metrics.
 # Notice also that the names of these functions should match the configuration.
 
-def get_stats_client_connections(db_connection):
+
+def get_stats_client_connections(_data_dir, db_connection):
     client_amount = get_client_connections_amount(db_connection)
     return [metric_client_connections(client_amount)]
 
 
-def get_stats_disk_usage_for_database(db_connection):
+def get_stats_disk_usage_for_database(_data_dir, db_connection):
     db_size = get_disk_usage_for_database(db_connection)
     return [metric_database_size(db_size[0], db_size[1])]
 
 
-def get_stats_tx_rate_for_database(db_connection):
+def get_stats_tx_rate_for_database(_data_dir, db_connection):
     db_name, tx_rate, tx_rollbacks = get_transaction_rate_for_database(db_connection)
     if tx_rate is not None:
         return [metric_transaction_rate(db_name, tx_rate),
@@ -85,15 +95,15 @@ def get_stats_tx_rate_for_database(db_connection):
         return []
 
 
-def get_stats_seconds_since_last_vacuum_per_table(db_connection):
+def get_stats_seconds_since_last_vacuum_per_table(_data_dir, db_connection):
     last_vacuums_data = get_seconds_since_last_vacuum_per_table(db_connection)
     metrics = []
     for db_name, table_name, seconds_since in last_vacuums_data:
         metrics.append(metric_seconds_since_last_vacuum(db_name, table_name, seconds_since))
     return metrics
 
 
-def get_stats_heap_hit_statistics(db_connection):
+def get_stats_heap_hit_statistics(_data_dir, db_connection):
     db_name, heap_read, heap_hit, heap_hit_ratio = get_heap_hit_statistics(db_connection)
     metrics = []
     if heap_hit_ratio is not None:
@@ -103,7 +113,7 @@ def get_stats_heap_hit_statistics(db_connection):
     return metrics
 
 
-def get_stats_lock_statistics(db_connection):
+def get_stats_lock_statistics(_data_dir, db_connection):
     locks_by_type, [total_locks_waiting, total_locks_granted] = get_lock_statistics(db_connection)
     metrics = []
     for lock_type, [locks_waiting, locks_granted] in locks_by_type.items():
@@ -114,15 +124,15 @@ def get_stats_lock_statistics(db_connection):
     return metrics
 
 
-def get_stats_oldest_transaction_timestamp(db_connection):
+def get_stats_oldest_transaction_timestamp(_data_dir, db_connection):
     db_name, sec_since_oldest_xact_start = get_oldest_transaction_timestamp(db_connection)
     metrics = []
     if sec_since_oldest_xact_start is not None:
         metrics.append(metric_sec_since_oldest_xact_start(db_name, sec_since_oldest_xact_start))
     return metrics
 
 
-def get_stats_table_bloat(db_connection):
+def get_stats_table_bloat(_data_dir, db_connection):
     tables_with_oids = get_tables_with_oids_for_current_db(db_connection)
     metrics = []
     for table_oid, table_name in tables_with_oids:
@@ -132,7 +142,7 @@ def get_stats_table_bloat(db_connection):
     return metrics
 
 
-def get_stats_index_hit_rates(db_connection):
+def get_stats_index_hit_rates(_data_dir, db_connection):
     index_hit_rates = get_index_hit_rates(db_connection)
     metrics = []
     for db_name, table_name, index_hit_ratio in index_hit_rates:
@@ -141,18 +151,56 @@ def get_stats_index_hit_rates(db_connection):
     return metrics
 
 
-def get_stats_replication_delays(db_connection):
+def get_stats_replication_delays(_data_dir, db_connection):
     replication_delays = get_replication_delays(db_connection)
     metrics = []
     for client_addr, delay_in_bytes in replication_delays:
         metrics.append(metric_replication_delay_bytes(client_addr, delay_in_bytes))
     return metrics
 
 
-def get_stats_wal_file_amount(data_dir):
+def _get_multixact_members(data_dir):
+    return get_multixact_member_files(data_dir) * MEMBERS_PER_MEMBER_FILE
+
+
+def get_multixact_members_per_mxid(data_dir, db_connection):
+    members = _get_multixact_members(data_dir)
+    mxid_age = get_max_mxid_age(db_connection)
+    if not mxid_age:
+        return []
+    members_per_id = round(members / mxid_age, 2)
+    return [metric_multixact_members_per_mxid(members_per_id)]
+
+
+def get_multixact_members_remaining_ratio(data_dir, _db_connection):
+    members = _get_multixact_members(data_dir)
+    ratio = round(members / MAX_MULTIXACT_MEMBERS, 2)
+    percentage_remaining = (1.0 - ratio) * 100
+    return [metric_multixact_members_remaining_ratio(percentage_remaining)]
+
+
+def get_multixact_remaining_ratio(_data_dir, db_connection):
+    mxid_age = get_max_mxid_age(db_connection)
+    if not mxid_age:
+        return []
+    ratio = round(mxid_age / WRAPAROUND_LIMIT, 2)
+    percentage_remaining = (1.0 - ratio) * 100
+    return [metric_multixact_remaining_ratio(percentage_remaining)]
+
+
+def get_xid_remaining_ratio(_data_dir, db_connection):
+    xid_age = get_max_xid_age(db_connection)
+    if not xid_age:
+        return []
+    ratio = round(xid_age / WRAPAROUND_LIMIT, 2)
+    percentage_remaining = (1.0 - ratio) * 100
+    return [metric_xid_remaining_ratio(percentage_remaining)]
+
+
+def get_stats_wal_file_amount(data_dir, _db_connection):
     return [metric_wal_file_amount(get_amount_of_wal_files(data_dir))]
 
 
-def get_stats_incoming_replication_status(db_connection):
+def get_stats_incoming_replication_status(_data_dir, db_connection):
     return [metric_incoming_replication_running(host, is_streaming)
             for host, is_streaming in get_wal_receiver_status(db_connection)]

postgresql_metrics/metrics_logic.py

@@ -82,7 +82,7 @@ def _is_time_to_call_stats_func_and_update_ts(database_name, metrics_func, run_i
     return False
 
 
-def _call_all_db_functions(db_parameter, db_stats_functions, schedule=False, db_name=None):
+def _call_all_db_functions(db_stats_functions, db_parameters, schedule=False, db_name=None):
     """Iterates through all given statistics functions, calling them with the given parameter.
     The db_parameter can be a database connection or a file path to Postgres data directory,
     depending on the statistics function to call.
@@ -100,7 +100,7 @@ def _call_all_db_functions(db_parameter, db_stats_functions, schedule=False, db_
         if is_call_required:
             try:
                 LOG.debug('calling stats function {}', db_metrics_func.__name__)
-                metrics.extend(db_metrics_func(db_parameter))
+                metrics.extend(db_metrics_func(*db_parameters))
             except Exception:
                 LOG.exception('failed calling stats function: ' + db_metrics_func.__name__)
     return metrics
@@ -123,22 +123,25 @@ def get_stats_functions_from_conf(func_key_name, conf):
 def get_all_stats_functions_from_conf(conf):
     db_functions = get_stats_functions_from_conf('db_functions', conf)
     global_db_functions = get_stats_functions_from_conf('global_db_functions', conf)
+    # `data_dir_functions` is deprecated, but to preserve backwards compatibility still read
     data_dir_functions = get_stats_functions_from_conf('data_dir_functions', conf)
-    return db_functions, global_db_functions, data_dir_functions
+    if data_dir_functions:
+        LOG.warn("data_dir_functions field in config is deprecated -- consider moving functions to global_db_functions")
+    all_global_db_functions = data_dir_functions + global_db_functions
+    return db_functions, all_global_db_functions
 
 
 def get_all_metrics_now(db_connections, conf):
     """Get all the metrics immediately without any scheduling.
     First gets the global stats with first available database connection,
     and then gets the rest per database.
     """
-    db_functions, global_db_functions, data_dir_functions = get_all_stats_functions_from_conf(conf)
+    db_functions, global_db_functions = get_all_stats_functions_from_conf(conf)
     data_dir = figure_out_postgres_data_dir(db_connections[0], conf)
 
-    all_metrics = _call_all_db_functions(db_connections[0], global_db_functions)
-    all_metrics.extend(_call_all_db_functions(data_dir, data_dir_functions))
+    all_metrics = _call_all_db_functions(global_db_functions, (data_dir, db_connections[0]))
     for db_connection in db_connections:
-        all_metrics.extend(_call_all_db_functions(db_connection, db_functions))
+        all_metrics.extend(_call_all_db_functions(db_functions, (data_dir, db_connection)))
     return all_metrics
 
 
@@ -147,14 +150,13 @@ def get_all_metrics_scheduled(db_connections, conf):
     First gets the global stats with first available database connection,
     and then gets the rest per database.
     """
-    db_functions, global_db_functions, data_dir_functions = get_all_stats_functions_from_conf(conf)
+    db_functions, global_db_functions = get_all_stats_functions_from_conf(conf)
     data_dir = figure_out_postgres_data_dir(db_connections[0], conf)
 
-    all_metrics = _call_all_db_functions(db_connections[0], global_db_functions, schedule=True)
-    all_metrics.extend(_call_all_db_functions(data_dir, data_dir_functions, schedule=True))
+    all_metrics = _call_all_db_functions(global_db_functions, (data_dir, db_connections[0]), schedule=True)
     for db_connection in db_connections:
         db_name = get_db_name_from_connection(db_connection)
-        all_metrics.extend(_call_all_db_functions(db_connection, db_functions,
+        all_metrics.extend(_call_all_db_functions(db_functions, (data_dir, db_connection),
                                                   schedule=True, db_name=db_name))
     return all_metrics
 

postgresql_metrics/postgres_queries.py

@@ -195,6 +195,28 @@ def get_oldest_transaction_timestamp(conn):
     return None, None
 
 
+def get_max_mxid_age(conn):
+    # `mxid_age` is only available on postgres 9.5 and newer
+    if conn.server_version < 95000:
+        LOG.error("Unable to check mxid_age on versions of postgres below 9.5")
+        return None
+    sql = "SELECT max(mxid_age(relminmxid)) FROM pg_class WHERE relminmxid <> '0'"
+    results = query(conn, sql)
+    if not results:
+        return None
+    mxid_age, = results[0]
+    return int(mxid_age)
+
+
+def get_max_xid_age(conn):
+    sql = "SELECT max(age(datfrozenxid)) FROM pg_database"
+    results = query(conn, sql)
+    if not results:
+        return None
+    xid_age, = results[0]
+    return int(xid_age)
+
+
 def get_replication_delays(conn):
     sql = ("SELECT client_addr, "
            "pg_xlog_location_diff(pg_current_xlog_location(), replay_location) AS bytes_diff "