Merge pull request #384 from CartoDB/federated_diagnostics_latency

Federated diagnostics latency

scripts-available/CDB_FederatedServerDiagnostics.sql

@@ -98,6 +98,102 @@ $$
 LANGUAGE SQL VOLATILE PARALLEL UNSAFE;
 
 
+--
+-- Get a foreign PG server hostname from the catalog
+--
+CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_Foreign_Server_Host_PG(server_internal name)
+RETURNS text
+AS $$
+    SELECT option_value FROM (
+        SELECT (pg_options_to_table(srvoptions)).*
+        FROM pg_foreign_server WHERE srvname = server_internal
+    ) AS opt WHERE opt.option_name = 'host';
+$$
+LANGUAGE SQL VOLATILE PARALLEL UNSAFE;
+
+
+--
+-- Get a foreign PG server port from the catalog
+--
+CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_Foreign_Server_Port_PG(server_internal name)
+RETURNS integer
+AS $$
+    SELECT option_value::integer FROM (
+        SELECT (pg_options_to_table(srvoptions)).*
+        FROM pg_foreign_server WHERE srvname = server_internal
+    ) AS opt WHERE opt.option_name = 'port';
+$$
+LANGUAGE SQL VOLATILE PARALLEL UNSAFE;
+
+--
+-- Get one measure of network latency in ms to a remote TCP server
+--
+CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_TCP_Foreign_Server_Latency(
+    server_internal name,
+    timeout_seconds float DEFAULT 5.0,
+    n_samples integer DEFAULT 10
+)
+RETURNS jsonb
+AS $$
+    import socket
+    import json
+    import math
+    from timeit import default_timer as timer
+
+    plan = plpy.prepare("SELECT @extschema@.__CDB_FS_Foreign_Server_Host_PG($1) AS host", ['name'])
+    rv = plpy.execute(plan, [server_internal], 1)
+    host = rv[0]['host']
+
+    plan = plpy.prepare("SELECT @extschema@.__CDB_FS_Foreign_Server_Port_PG($1) AS port", ['name'])
+    rv = plpy.execute(plan, [server_internal], 1)
+    port = rv[0]['port'] or 5432
+
+    n_errors = 0
+    samples = []
+
+    for i in range(n_samples):
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.settimeout(timeout_seconds)
+
+        t_start = timer()
+
+        try:
+            s.connect((host, int(port)))
+            t_stop = timer()
+            s.shutdown(socket.SHUT_RD)
+        except (socket.timeout, OSError, socket.error) as ex:
+            plpy.warning('could not connect to server %s:%d, %s' % (host, port, str(ex)))
+            n_errors += 1
+        finally:
+            s.close()
+
+        t_connect = (t_stop - t_start) * 1000.0
+        plpy.debug('TCP connection %s:%d time=%.2f ms' % (host, port, t_connect))
+        samples.append(t_connect)
+
+    stats = {
+        'n_samples': n_samples,
+        'n_errors': n_errors,
+    }
+    n = len(samples)
+    if n >= 1:
+        mean = sum(samples) / n
+        stats.update({
+            'avg': round(mean, 3),
+            'min': round(min(samples), 3),
+            'max': round(max(samples), 3)
+        })
+    if n >= 2:
+        var = sum([ (x - mean)**2 for x in samples ]) / (n-1)
+        stdev = math.sqrt(var)
+        stats.update({
+            'stdev': round(stdev, 3)
+        })
+    return json.dumps(stats)
+$$
+LANGUAGE plpythonu VOLATILE PARALLEL UNSAFE;
+
+
 --
 -- Collect and return diagnostics info from a remote PG into a jsonb
 --
@@ -105,14 +201,16 @@ CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_Server_Diagnostics_PG(server_int
 RETURNS jsonb
 AS $$
 DECLARE
-    remote_server_version  text := @extschema@.__CDB_FS_Foreign_Server_Version_PG(server_internal);
-    remote_postgis_version text := @extschema@.__CDB_FS_Foreign_PostGIS_Version_PG(server_internal);
-    remote_server_options jsonb := @extschema@.__CDB_FS_Foreign_Server_Options_PG(server_internal);
+    remote_server_version  text    := @extschema@.__CDB_FS_Foreign_Server_Version_PG(server_internal);
+    remote_postgis_version text    := @extschema@.__CDB_FS_Foreign_PostGIS_Version_PG(server_internal);
+    remote_server_options jsonb    := @extschema@.__CDB_FS_Foreign_Server_Options_PG(server_internal);
+    remote_server_latency_ms jsonb := @extschema@.__CDB_FS_TCP_Foreign_Server_Latency(server_internal);
 BEGIN
     RETURN jsonb_build_object(
         'server_version', remote_server_version,
         'postgis_version', remote_postgis_version,
-        'server_options', remote_server_options
+        'server_options', remote_server_options,
+        'server_latency_ms', remote_server_latency_ms
     );
 END
 $$