apm-agent-php and xdebug extensions enabled together cause a memory leak in php7.4-fpm

[MemoryLeak55]

Describe the bug

Using nginx + php7.4-fpm with extensions apm-agent-php and xdebug enabled together cause memory leak. Disabling either stops the leak.

To Reproduce

I have reproduced this issue in a docker container.

Dockerfile

FROM ubuntu:20.04

RUN  apt update && \
    DEBIAN_FRONTEND=noninteractive apt install -y \
    php \
    php-fpm \
    nginx \
    curl \
    wget \
    openssl \
    ca-certificates \
    php-xdebug

RUN apt purge -y apache2

RUN echo  \
    'server { \
            listen 80 default_server; \
            server_name localhost; \
location ~ ^/status$ { \
        allow 127.0.0.1;\
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;\
        fastcgi_index index.php;\
        include fastcgi_params;\
        fastcgi_pass   unix:/var/run/php/php7.4-fpm.sock;\
}\
    }' > /etc/nginx/sites-available/default 

RUN sed -i 's#;pm.status_path = /status#pm.status_path = /status#g' /etc/php/7.4/fpm/pool.d/www.conf

# These here are the two critical lines. xdebug is enabled by default if it's installed
# Uncomment the next line to stop the leak
# RUN phpdismod xdebug

#OR comment this line to stop the leak
RUN wget https://github.com/elastic/apm-agent-php/releases/download/v1.3/apm-agent-php_1.3_all.deb && dpkg -i apm-agent-php_1.3_all.deb

CMD php-fpm7.4 && nginx && nginx -s reload && watch -n1 curl http://localhost/status?full

Then, to build and run it:

docker build . -t leak
docker run -it leak

Observe the php-fpm memory using htop or similar on the host and watch memory increase without being released.

Command for convenience

top -E m -c -p $(pgrep -d',' -f 'php-fpm:')

Expected behavior No memory leak when both are enabled.

[waynegemmell]

Hi, any feedback on this? We're experiencing the same issue.

[abra7134]

And we also faced this problem but on php7.2.

This pool handled only/status requests

127.0.0.1 -  14/Dec/2022:13:30:57 +0300 "GET /status" 200
127.0.0.1 -  14/Dec/2022:13:30:57 +0300 "GET /status" 200
127.0.0.1 -  14/Dec/2022:13:31:07 +0300 "GET /status" 200
127.0.0.1 -  14/Dec/2022:13:31:07 +0300 "GET /status" 200

Application versions:

• Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies with Zend OPcache v7.2.33-1+ubuntu20.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies with Xdebug v2.9.6, Copyright (c) 2002-2020, by Derick Rethans
• Elastic APM PHP installed from https://github.com/elastic/apm-agent-php/releases/download/v1.6.1/apm-agent-php_1.6.1_all.deb

Xdebug and APM agent with default settings.

[SergeyKleyman]

@thomas-thorburn-connect , @abra7134 @waynegemmell Did you have a chance to try the latest agent release (v1.10.0) - does it still result in memory leak?

[MemoryLeak55]

@SergeyKleyman On ubuntu 20.04 with php7.4-fpm apm agent v1.10.0 still leaks, on ubuntu 22.04 with php7.4-fpm there is no leak on ubuntu 22.04 with php8.1-fpm there is no leak

updated dockerfiles to reproduce leak on 20.04 and show no leak on 22.04

ubuntu 20.04 php 7.4

FROM ubuntu:20.04

RUN  apt update && \
    DEBIAN_FRONTEND=noninteractive apt install -y \
    php \
    php-fpm \
    nginx \
    curl \
    wget \
    openssl \
    ca-certificates \
    php-xdebug

RUN apt purge -y apache2

RUN echo  \
    'server { \
            listen 80 default_server; \
            server_name localhost; \
location ~ ^/status$ { \
        allow 127.0.0.1;\
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;\
        fastcgi_index index.php;\
        include fastcgi_params;\
        fastcgi_pass   unix:/var/run/php/php7.4-fpm.sock;\
}\
    }' > /etc/nginx/sites-available/default

RUN sed -i 's#;pm.status_path = /status#pm.status_path = /status#g' /etc/php/7.4/fpm/pool.d/www.conf

# These here are the two critical lines. xdebug is enabled by default if it's installed
# Uncomment the next line to stop the leak
# RUN phpdismod xdebug

#OR comment this line to stop the leak
RUN wget https://github.com/elastic/apm-agent-php/releases/download/v1.10.0/apm-agent-php_1.10.0_all.deb && dpkg -i apm-agent-php_1.10.0_all.deb

CMD php-fpm7.4 && nginx && nginx -s reload && watch -n1 curl http://localhost/status?full

ubuntu 22.04 php 8.1

FROM ubuntu:22.04

RUN  apt update && \
    DEBIAN_FRONTEND=noninteractive apt install -y \
    php \
    php-fpm \
    nginx \
    curl \
    wget \
    openssl \
    ca-certificates \
    php-xdebug

RUN apt purge -y apache2

RUN echo  \
    'server { \
            listen 80 default_server; \
            server_name localhost; \
location ~ ^/status$ { \
        allow 127.0.0.1;\
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;\
        fastcgi_index index.php;\
        include fastcgi_params;\
        fastcgi_pass   unix:/var/run/php/php8.1-fpm.sock;\
}\
    }' > /etc/nginx/sites-available/default

RUN sed -i 's#;pm.status_path = /status#pm.status_path = /status#g' /etc/php/8.1/fpm/pool.d/www.conf

# These here are the two critical lines. xdebug is enabled by default if it's installed
# Uncomment the next line to stop the leak
# RUN phpdismod xdebug

#OR comment this line to stop the leak
RUN wget https://github.com/elastic/apm-agent-php/releases/download/v1.10.0/apm-agent-php_1.10.0_all.deb && dpkg -i apm-agent-php_1.10.0_all.deb

CMD php-fpm8.1 && nginx && nginx -s reload && watch -n1 curl http://localhost/status?full

ubuntu 22.04 php 7.4

FROM ubuntu:22.04

RUN apt update && apt install -y software-properties-common

RUN add-apt-repository ppa:ondrej/php -y

RUN  apt update && \
    DEBIAN_FRONTEND=noninteractive apt install -y \
    php7.4 \
    php7.4-fpm \
    nginx \
    curl \
    wget \
    openssl \
    ca-certificates \
    php7.4-xdebug

RUN apt purge -y apache2

RUN update-alternatives --set php /usr/bin/php7.4

RUN echo  \
    'server { \
            listen 80 default_server; \
            server_name localhost; \
location ~ ^/status$ { \
        allow 127.0.0.1;\
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;\
        fastcgi_index index.php;\
        include fastcgi_params;\
        fastcgi_pass   unix:/var/run/php/php7.4-fpm.sock;\
}\
    }' > /etc/nginx/sites-available/default

RUN sed -i 's#;pm.status_path = /status#pm.status_path = /status#g' /etc/php/7.4/fpm/pool.d/www.conf

# These here are the two critical lines. xdebug is enabled by default if it's installed
# Uncomment the next line to stop the leak
# RUN phpdismod xdebug
RUN phpenmod xdebug
#OR comment this line to stop the leak
RUN wget https://github.com/elastic/apm-agent-php/releases/download/v1.10.0/apm-agent-php_1.10.0_all.deb && dpkg -i apm-agent-php_1.10.0_all.deb

RUN mkdir -p /run/php
CMD php-fpm7.4 && sleep 5 && nginx && nginx -s reload && watch -n0.1 curl http://localhost/status?full