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Date: Mon, 06 Feb 2017 01:18:12 +0700
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: internals <internals@lists.php.net>, Laruence <laruence@php.net>,
 alexvmesh@gmail.com, artyomnsk2012@gmail.com
In-Reply-To: <CAF+90c8y7Vg5FcYYg2hB1c0B3izc8mhPyMRewkGzauYUbAA9Yw@mail.gmail.com>
References: <48a7eb6950ea9a1f512937f138dd5fb9@andb.name>
 <CAF+90c8y7Vg5FcYYg2hB1c0B3izc8mhPyMRewkGzauYUbAA9Yw@mail.gmail.com>
Message-ID: <e17d138a123e4e06592ac14f1ee81f68@andb.name>
User-Agent: Roundcube Webmail/1.3-git
Subject: Re: [PHP-DEV] Need help with strange and random bug
From: andrey@andb.name (Andrey E Baranov)

Nikita Popov at 2017-02-05 21:44 wrote:
> On Sun, Feb 5, 2017 at 3:03 PM, Andrey E Baranov <andrey@andb.name> 
> wrote:
> 
>> Hi all,
>> 
>> I have problem, debug is not yet finished, and for now do not can
>> reproduce, problem occurs only in production (after migrate to PHP7).
>> perhaps someone else can help :)
>> PHP 7.0.13 (Ubuntu 16.04 package repository), php-fpm
>> 
>> For simplify:
>> ```
>> ...
>> Log::debug('1:' . print_r($video, true));
>> Log::debug('2:' . json_encode($video) . ' json_last_error: ' .
>> json_last_error() . ' json_last_error_msg: ' . json_last_error_msg());
>> 
>> $video['delivery'] = [2]; // after this line: serialize and 
>> json_encode do
>> not work as expected
>> 
>> Log::debug('3:' . print_r($video, true));
>> Log::debug('4:' . serialize($video));
>> Log::debug('5:' . json_encode($video) . ' json_last_error: ' .
>> json_last_error() . ' json_last_error_msg: ' . json_last_error_msg());
>> ...
>> ```
>> 
>> log with bug:
>> ```
>> DEBUG: 1:Array
>> (
>>     [mimes] => Array
>>         (
>>             [0] => video/mp4
>>         )
>> 
>>     [linearity] => 1
>>     [minduration] => 5
>>     [maxduration] => 60
>>     [protocols] => Array
>>         (
>>             [0] => 2
>>             [1] => 3
>>         )
>> 
>>     [w] => 818
>>     [h] => 460
>>     [minbitrate] => 100
>>     [maxbitrate] => 1200
>> )
>> DEBUG: 2: {"mimes":["video/mp4"],"linearity":1,"minduration":5,"maxdur
>> ation":60,"protocols":[2,3],"w":818,"h":460,"minbitrate":
>> 100,"maxbitrate":1200}
>> DEBUG: 3:Array
>> (
>>     [mimes] => Array
>>         (
>>             [0] => video/mp4
>>         )
>> 
>>     [linearity] => 1
>>     [minduration] => 5
>>     [maxduration] => 60
>>     [protocols] => Array
>>         (
>>             [0] => 2
>>             [1] => 3
>>         )
>> 
>>     [w] => 818
>>     [h] => 460
>>     [minbitrate] => 100
>>     [maxbitrate] => 1200
>>     [delivery] => Array
>>         (
>>             [0] => 2
>>         )
>> 
>> )
>> DEBUG: 4:a:10:{s:5:"mimes";a:1:{i:0;s:9:"video/mp4";}s:9:"linearity
>> ";i:1;s:11:"minduration";i:5;s:11:"maxduration";i:60;s:9:"p
>> rotocols";a:2:{i:0;i:2;i:1;i:3;}s:1:"w";i:818;s:1:"h";i:460;
>> s:10:"minbitrate";i:100;s:10:"maxbitrate";i:1200;s:8:"delivery";N;}
>> DEBUG: 5: json_last_error: 6 json_last_error_msg: Recursion detected
>> ```
>> 
>> - 4: `serialize($video)` - `"delivery";N;` - it is mean that 
>> `delivery` is
>> Null - that is not true
>> - 5: `json_encode($video)` - Recursion detected
>> 
>> Problem occurs in random period after start fpm process (after 10..30
>> min), and remains constant until restart fpm
>> 
>> Same problem as I see in http://stackoverflow.com/quest
>> ions/37456845/what-does-json-error-recursion-mean-from-json-encode
>> 
>> After deep analyze:
>> 
>> php_json_encode_array:
>> ```
>> ```
>> if (myht && ZEND_HASH_GET_APPLY_COUNT(myht) > 1) {
>>   JSON_G(error_code) = PHP_JSON_ERROR_RECURSION;
>>   smart_str_appendl(buf, "null", 4);
>>   return;
>> }
>> ```
>> 
>> serialize:
>> ```
>> if (... || (Z_TYPE_P(data) == IS_ARRAY && 
>> Z_ARRVAL_P(data)->u.v.nApplyCount
>> > 1)
>>   ) {
>>     smart_str_appendl(buf, "N;", 2);
>> ...
>> ```
>> 
>> so looks like problem in `HashTable.v.nApplyCount`
>> 
>> 
>> Also I am find commit - https://github.com/php/php-src
>> /commit/d26ca894020bc28eb55b153fac5548374d5ce16d
>> 
>> In this commit added
>> ```
>> target->u.flags = (source->u.flags & 
>> ~(...|ZEND_HASH_APPLY_COUNT_MASK))...
>> ```
>> But not added to case if `if (GC_FLAGS(source) & IS_ARRAY_IMMUTABLE)` 
>> -
>> maybe need fix in this place? :) I guess that the problem in immutable
>> arrays.
>> 
> 
> The apply count on immutable arrays is always zero, so this shouldn't 
> be a
> problem. However, it may be that some other code is incrementing the 
> apply
> count on an immutable array. Can you please check whether running with
> opcache.protect_memory=1 gives you any segmentation faults or bus 
> errors?
> 
> Nikita

Nikita thanks! looks like `opcache.protect_memory=1` is usefull :)

```
#0  phongo_bson_append (bson=bson@entry=0x7fff0d47e220,
     flags=flags@entry=PHONGO_BSON_NONE, key=0x7fabe79ec070 "$in", 
key_len=3,
     entry=entry@entry=0x7fabe7f79a00) at 
/tmp/pear/temp/mongodb/src/bson.c:1027
...
```

and it is fixed in
https://github.com/mongodb/mongo-php-driver/commit/129753881a223b8378fc7b8137104c65d8d8828f

so, with PHP7 need use mongodb >= 1.1.10 (as minimum :) we missed that 
mongodb is outdated in our production, but the relationship between our 
bug and mongodb was not the obvious)