Disabling Connection persistence

[sameer1750]

Hello,
Regarding your Comment

1. moving the initializing of the pclients hash table from GINIT (here) to RINIT
2. moving the destruction of the pclients hash table from MSHUTDOWN (here) to RSHUTDOWN.

Where exactly do we need to change in the code to disable connection persistence.

[jmikola]

If you're willing to share, I'd be curious to know what your use case is for needing this patch. As I've explained in many prior threads on the subject, disabling connection persistence is not a reliable solution for addressing high connection counts on the server. A high number of incoming requests could still spawn enough PHP workers to overwhelm the server and without persistence each request will require additional time to connect to and discover the topology. A more robust solution entails tuning behavior for the PHP worker pool.

That said, the following patch implements the change I originally suggested in #564 (comment) and later referenced in #732 (comment), which you linked. This patch is based on the 1.5.3 release source:

diff --git a/php_phongo.c b/php_phongo.c
index 497a8a18..f33e3dbd 100644
--- a/php_phongo.c
+++ b/php_phongo.c
@@ -2799,6 +2799,9 @@ PHP_RINIT_FUNCTION(mongodb)
                zend_hash_init(MONGODB_G(subscribers), 0, NULL, ZVAL_PTR_DTOR, 0);
        }
 
+       /* Initialize HashTable for persistent clients */
+       zend_hash_init_ex(&MONGODB_G(pclients), 0, NULL, php_phongo_pclient_dtor, 1, 0);
+
        return SUCCESS;
 }
 /* }}} */
@@ -2819,9 +2822,6 @@ PHP_GINIT_FUNCTION(mongodb)
 #endif
        memset(mongodb_globals, 0, sizeof(zend_mongodb_globals));
        mongodb_globals->bsonMemVTable = bsonMemVTable;
-
-       /* Initialize HashTable for persistent clients */
-       zend_hash_init_ex(&mongodb_globals->pclients, 0, NULL, php_phongo_pclient_dtor, 1, 0);
 }
 /* }}} */
 
@@ -2976,10 +2976,6 @@ PHP_MSHUTDOWN_FUNCTION(mongodb)
 {
        (void) type; /* We don't care if we are loaded via dl() or extension= */
 
-       /* Destroy HashTable for persistent clients. The HashTable destructor will
-        * destroy any mongoc_client_t objects that were created by this process. */
-       zend_hash_destroy(&MONGODB_G(pclients));
-
        bson_mem_restore_vtable();
        /* Cleanup after libmongoc */
        mongoc_cleanup();
@@ -3000,6 +2996,10 @@ PHP_RSHUTDOWN_FUNCTION(mongodb)
                MONGODB_G(subscribers) = NULL;
        }
 
+       /* Destroy HashTable for persistent clients. The HashTable destructor will
+        * destroy any mongoc_client_t objects that were created by this process. */
+       zend_hash_destroy(&MONGODB_G(pclients));
+
        return SUCCESS;
 }
 /* }}} */

To test this, I used the following basic script to execute a ping command on the local server:

<?php

$m = new MongoDB\Driver\Manager;
$c = $m->executeCommand('test', new MongoDB\Driver\Command(['ping' => 1]));
var_dump($c->toArray()[0]);

I then accessed the above script through PHP's built-in web server (php -S localhost:8080 -t .) and observed the MongoDB server's logs for connection activity.

With the patch in place to disable persistence, we see a connection open and close for each corresponding web request:

2019-03-27T11:28:51.961-0400 I NETWORK  [listener] connection accepted from 127.0.0.1:37446 #1 (1 connection now open)
2019-03-27T11:28:51.961-0400 I NETWORK  [conn1] received client metadata from 127.0.0.1:37446 conn1: { driver: { name: "mongoc / ext-mongodb:PHP", version: "1.13.0 / 1.5.3" }, os: { type: "Linux", name: "Ubuntu", version: "18.04", architecture: "x86_64" }, platform: "cfg=0x515620c9 posix=200809 stdc=201112 CC=GCC 7.3.0 CFLAGS="-g  -O0" LDFLAGS="" / PHP 7.2.11" }
2019-03-27T11:28:51.962-0400 I NETWORK  [conn1] end connection 127.0.0.1:37446 (0 connections now open)
2019-03-27T11:29:14.409-0400 I NETWORK  [listener] connection accepted from 127.0.0.1:37452 #2 (1 connection now open)
2019-03-27T11:29:14.410-0400 I NETWORK  [conn2] received client metadata from 127.0.0.1:37452 conn2: { driver: { name: "mongoc / ext-mongodb:PHP", version: "1.13.0 / 1.5.3" }, os: { type: "Linux", name: "Ubuntu", version: "18.04", architecture: "x86_64" }, platform: "cfg=0x515620c9 posix=200809 stdc=201112 CC=GCC 7.3.0 CFLAGS="-g  -O0" LDFLAGS="" / PHP 7.2.11" }
2019-03-27T11:29:14.412-0400 I NETWORK  [conn2] end connection 127.0.0.1:37452 (0 connections now open)

Without the patch, we see the following server log output in tandem with the first web request:

2019-03-27T11:30:36.475-0400 I NETWORK  [listener] connection accepted from 127.0.0.1:37526 #12 (1 connection now open)
2019-03-27T11:30:36.475-0400 I NETWORK  [conn12] received client metadata from 127.0.0.1:37526 conn12: { driver: { name: "mongoc / ext-mongodb:PHP", version: "1.9.1-dev / 1.4.0-dev" }, os: { type: "Linux", name: "Ubuntu", version: "18.04", architecture: "x86_64" }, platform: "cfg=0x156b8e9 posix=200809 stdc=201112 CC=GCC 5.4.0 20160609 CFLAGS="-g  -O0" LDFLAGS="" / PHP 7.0.25" }

The connection is not closed as the request completes and subsequent web requests will not open a new connection. We will ultimately see this connection closed when the php process terminates.

[shengli881026]

No suitable servers found (serverSelectionTryOnce set): [connection closed calling ismaster on 。
Solve it, man.

[jmikola]

Closing, as my previous comment describes how to patch the driver to disable connection persistence.