php-fpm fails after X requests

Matthew Weeks asked:

I using nginx to serve out a PHP CMS (Grav) so I’ve been using php-fpm.

Everything works fine in the beginning, but after about 20 or so requests, some of the pages will return a 502 error. I don’t have any control over the PHP code, and it’s even been updated recently and that hasn’t fixed it so I’m not sure the problem is with the CMS (nobody else seems to be vocalizing this problem).

Whenever I restart php-fpm it fixes the problem. The weird part is not all of the routes on the website are broken, and if I run a cache clear on the CMS it also seems to fix it.

To make things even weirder, when it initially breaks and I try to access it at https://www.example.com, I get the 502 error. But when I access it at http://example.com, it works fine. If enough requests go to both it seems they both break

My nginx configuration looks like the following:

server {
  listen 443 ssl;
  server_name www.example.com example.com;

  ssl_certificate /etc/nginx/ssl/example.crt;
  ssl_certificate_key /etc/ssl/private/example.key;

  root /srv/www/example.com;
  index index.php;
  access_log  /var/log/nginx/example.access.log;
  error_log  /var/log/nginx/example.error.log;

  location / {
    try_files $uri $uri/ /index.php?$query_string;
  }


  location ~ \.php$ {
    # fastcgi_pass unix:/var/run/php-fpm/php-fpm.sock;
    fastcgi_pass 127.0.0.1:9000;
    fastcgi_split_path_info ^(.+\.php)(/.+)$;
    fastcgi_index index.php;
    include fastcgi_params;
    fastcgi_param SCRIPT_FILENAME $document_root/$fastcgi_script_name;
  }
}

And my php-fpm configuration looks like the following:

; Start a new pool named 'www'.
[www]

; Unix user/group of processes
; Note: The user is mandatory. If the group is not set, the default user's group
;       will be used.
; RPM: apache Choosed to be able to access some dir as httpd
user = nginx
; RPM: Keep a group allowed to write in log dir.
group = nginx

; The address on which to accept FastCGI requests.
; Valid syntaxes are:
;   'ip.add.re.ss:port'    - to listen on a TCP socket to a specific IPv4 address on
;                            a specific port;
;   '[ip:6:addr:ess]:port' - to listen on a TCP socket to a specific IPv6 address on
;                            a specific port;
;   'port'                 - to listen on a TCP socket to all addresses
;                            (IPv6 and IPv4-mapped) on a specific port;
;   '/path/to/unix/socket' - to listen on a unix socket.
; Note: This value is mandatory.
;listen = /var/run/php-fpm/php-fpm.sock
listen = 127.0.0.1:9000

; Set listen(2) backlog.
; Default Value: 511 (-1 on FreeBSD and OpenBSD)
;listen.backlog = 511

; Set permissions for unix socket, if one is used. In Linux, read/write
; permissions must be set in order to allow connections from a web server. Many
; BSD-derived systems allow connections regardless of permissions.
; Default Values: user and group are set as the running user
;                 mode is set to 0660
listen.owner = nginx
listen.group = nginx
listen.mode = 0660
; When POSIX Access Control Lists are supported you can set them using
; these options, value is a comma separated list of user/group names.
; When set, listen.owner and listen.group are ignored
;listen.acl_users =
;listen.acl_groups =

; List of addresses (IPv4/IPv6) of FastCGI clients which are allowed to connect.
; Equivalent to the FCGI_WEB_SERVER_ADDRS environment variable in the original
; PHP FCGI (5.2.2+). Makes sense only with a tcp listening socket. Each address
; must be separated by a comma. If this value is left blank, connections will be
; accepted from any ip address.
; Default Value: any
listen.allowed_clients = 127.0.0.1

; Specify the nice(2) priority to apply to the pool processes (only if set)
; The value can vary from -19 (highest priority) to 20 (lower priority)
; Note: - It will only work if the FPM master process is launched as root
;       - The pool processes will inherit the master process priority
;         unless it specified otherwise
; Default Value: no set
; process.priority = -19

; Choose how the process manager will control the number of child processes.
; Possible Values:
;   static  - a fixed number (pm.max_children) of child processes;
;   dynamic - the number of child processes are set dynamically based on the
;             following directives. With this process management, there will be
;             always at least 1 children.
;             pm.max_children      - the maximum number of children that can
;                                    be alive at the same time.
;             pm.start_servers     - the number of children created on startup.
;             pm.min_spare_servers - the minimum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is less than this
;                                    number then some children will be created.
;             pm.max_spare_servers - the maximum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is greater than this
;                                    number then some children will be killed.
;  ondemand - no children are created at startup. Children will be forked when
;             new requests will connect. The following parameter are used:
;             pm.max_children           - the maximum number of children that
;                                         can be alive at the same time.
;             pm.process_idle_timeout   - The number of seconds after which
;                                         an idle process will be killed.
; Note: This value is mandatory.
pm = dynamic

; The number of child processes to be created when pm is set to 'static' and the
; maximum number of child processes when pm is set to 'dynamic' or 'ondemand'.
; This value sets the limit on the number of simultaneous requests that will be
; served. Equivalent to the ApacheMaxClients directive with mpm_prefork.
; Equivalent to the PHP_FCGI_CHILDREN environment variable in the original PHP
; CGI.
; Note: Used when pm is set to 'static', 'dynamic' or 'ondemand'
; Note: This value is mandatory.
pm.max_children = 50

; The number of child processes created on startup.
; Note: Used only when pm is set to 'dynamic'
; Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2
pm.start_servers = 5

; The desired minimum number of idle server processes.
; Note: Used only when pm is set to 'dynamic'
; Note: Mandatory when pm is set to 'dynamic'
pm.min_spare_servers = 5

; The desired maximum number of idle server processes.
; Note: Used only when pm is set to 'dynamic'
; Note: Mandatory when pm is set to 'dynamic'
pm.max_spare_servers = 35

; The number of seconds after which an idle process will be killed.
; Note: Used only when pm is set to 'ondemand'
; Default Value: 10s
;pm.process_idle_timeout = 10s;

; The number of requests each child process should execute before respawning.
; This can be useful to work around memory leaks in 3rd party libraries. For
; endless request processing specify '0'. Equivalent to PHP_FCGI_MAX_REQUESTS.
; Default Value: 0
;pm.max_requests = 500

; The URI to view the FPM status page. If this value is not set, no URI will be
; recognized as a status page. It shows the following informations:
;   pool                 - the name of the pool;
;   process manager      - static, dynamic or ondemand;
;   start time           - the date and time FPM has started;
;   start since          - number of seconds since FPM has started;
;   accepted conn        - the number of request accepted by the pool;
;   listen queue         - the number of request in the queue of pending
;                          connections (see backlog in listen(2));
;   max listen queue     - the maximum number of requests in the queue
;                          of pending connections since FPM has started;
;   listen queue len     - the size of the socket queue of pending connections;
;   idle processes       - the number of idle processes;
;   active processes     - the number of active processes;
;   total processes      - the number of idle + active processes;
;   max active processes - the maximum number of active processes since FPM
;                          has started;
;   max children reached - number of times, the process limit has been reached,
;                          when pm tries to start more children (works only for
;                          pm 'dynamic' and 'ondemand');
; Value are updated in real time.
; Example output:
;   pool:                 www
;   process manager:      static
;   start time:           01/Jul/2011:17:53:49 +0200
;   start since:          62636
;   accepted conn:        190460
;   listen queue:         0
;   max listen queue:     1
;   listen queue len:     42
;   idle processes:       4
;   active processes:     11
;   total processes:      15
;   max active processes: 12
;   max children reached: 0
;
; By default the status page output is formatted as text/plain. Passing either
; 'html', 'xml' or 'json' in the query string will return the corresponding
; output syntax. Example:
;   http://www.foo.bar/status
;   http://www.foo.bar/status?json
;   http://www.foo.bar/status?html
;   http://www.foo.bar/status?xml
;
; By default the status page only outputs short status. Passing 'full' in the
; query string will also return status for each pool process.
; Example:
;   http://www.foo.bar/status?full
;   http://www.foo.bar/status?json&full
;   http://www.foo.bar/status?html&full
;   http://www.foo.bar/status?xml&full
; The Full status returns for each process:
;   pid                  - the PID of the process;
;   state                - the state of the process (Idle, Running, ...);
;   start time           - the date and time the process has started;
;   start since          - the number of seconds since the process has started;
;   requests             - the number of requests the process has served;
;   request duration     - the duration in ┬Ás of the requests;
;   request method       - the request method (GET, POST, ...);
;   request URI          - the request URI with the query string;
;   content length       - the content length of the request (only with POST);
;   user                 - the user (PHP_AUTH_USER) (or '-' if not set);
;   script               - the main script called (or '-' if not set);
;   last request cpu     - the %cpu the last request consumed
;                          it's always 0 if the process is not in Idle state
;                          because CPU calculation is done when the request
;                          processing has terminated;
;   last request memory  - the max amount of memory the last request consumed
;                          it's always 0 if the process is not in Idle state
;                          because memory calculation is done when the request
;                          processing has terminated;
; If the process is in Idle state, then informations are related to the
; last request the process has served. Otherwise informations are related to
; the current request being served.
; Example output:
;   ************************
;   pid:                  31330
;   state:                Running
;   start time:           01/Jul/2011:17:53:49 +0200
;   start since:          63087
;   requests:             12808
;   request duration:     1250261
;   request method:       GET
;   request URI:          /test_mem.php?N=10000
;   content length:       0
;   user:                 -
;   script:               /home/fat/web/docs/php/test_mem.php
;   last request cpu:     0.00
;   last request memory:  0
;
; Note: There is a real-time FPM status monitoring sample web page available
;       It's available in: @[email protected]/fpm/status.html
;
; Note: The value must start with a leading slash (/). The value can be
;       anything, but it may not be a good idea to use the .php extension or it
;       may conflict with a real PHP file.
; Default Value: not set
;pm.status_path = /status

; The ping URI to call the monitoring page of FPM. If this value is not set, no
; URI will be recognized as a ping page. This could be used to test from outside
; that FPM is alive and responding, or to
; - create a graph of FPM availability (rrd or such);
; - remove a server from a group if it is not responding (load balancing);
; - trigger alerts for the operating team (24/7).
; Note: The value must start with a leading slash (/). The value can be
;       anything, but it may not be a good idea to use the .php extension or it
;       may conflict with a real PHP file.
; Default Value: not set
;ping.path = /ping

; This directive may be used to customize the response of a ping request. The
; response is formatted as text/plain with a 200 response code.
; Default Value: pong
;ping.response = pong

; The access log file
; Default: not set
;access.log = log/$pool.access.log

; The access log format.
; The following syntax is allowed
;  %%: the '%' character
;  %C: %CPU used by the request
;      it can accept the following format:
;      - %{user}C for user CPU only
;      - %{system}C for system CPU only
;      - %{total}C  for user + system CPU (default)
;  %d: time taken to serve the request
;      it can accept the following format:
;      - %{seconds}d (default)
;      - %{miliseconds}d
;      - %{mili}d
;      - %{microseconds}d
;      - %{micro}d
;  %e: an environment variable (same as $_ENV or $_SERVER)
;      it must be associated with embraces to specify the name of the env
;      variable. Some exemples:
;      - server specifics like: %{REQUEST_METHOD}e or %{SERVER_PROTOCOL}e
;      - HTTP headers like: %{HTTP_HOST}e or %{HTTP_USER_AGENT}e
;  %f: script filename
;  %l: content-length of the request (for POST request only)
;  %m: request method
;  %M: peak of memory allocated by PHP
;      it can accept the following format:
;      - %{bytes}M (default)
;      - %{kilobytes}M
;      - %{kilo}M
;      - %{megabytes}M
;      - %{mega}M
;  %n: pool name
;  %o: output header
;      it must be associated with embraces to specify the name of the header:
;      - %{Content-Type}o
;      - %{X-Powered-By}o
;      - %{Transfert-Encoding}o
;      - ....
;  %p: PID of the child that serviced the request
;  %P: PID of the parent of the child that serviced the request
;  %q: the query string
;  %Q: the '?' character if query string exists
;  %r: the request URI (without the query string, see %q and %Q)
;  %R: remote IP address
;  %s: status (response code)
;  %t: server time the request was received
;      it can accept a strftime(3) format:
;      %d/%b/%Y:%H:%M:%S %z (default)
;      The strftime(3) format must be encapsuled in a %{<strftime_format>}t tag
;      e.g. for a ISO8601 formatted timestring, use: %{%Y-%m-%dT%H:%M:%S%z}t
;  %T: time the log has been written (the request has finished)
;      it can accept a strftime(3) format:
;      %d/%b/%Y:%H:%M:%S %z (default)
;      The strftime(3) format must be encapsuled in a %{<strftime_format>}t tag
;      e.g. for a ISO8601 formatted timestring, use: %{%Y-%m-%dT%H:%M:%S%z}t
;  %u: remote user
;
; Default: "%R - %u %t \"%m %r\" %s"
;access.format = "%R - %u %t \"%m %r%Q%q\" %s %f %{mili}d %{kilo}M %C%%"

; The log file for slow requests
; Default Value: not set
; Note: slowlog is mandatory if request_slowlog_timeout is set
slowlog = /var/log/php-fpm/www-slow.log

; The timeout for serving a single request after which a PHP backtrace will be
; dumped to the 'slowlog' file. A value of '0s' means 'off'.
; Available units: s(econds)(default), m(inutes), h(ours), or d(ays)
; Default Value: 0
;request_slowlog_timeout = 0

; The timeout for serving a single request after which the worker process will
; be killed. This option should be used when the 'max_execution_time' ini option
; does not stop script execution for some reason. A value of '0' means 'off'.
; Available units: s(econds)(default), m(inutes), h(ours), or d(ays)
; Default Value: 0
;request_terminate_timeout = 0

; Set open file descriptor rlimit.
; Default Value: system defined value
;rlimit_files = 1024

; Set max core size rlimit.
; Possible Values: 'unlimited' or an integer greater or equal to 0
; Default Value: system defined value
;rlimit_core = 0

; Chroot to this directory at the start. This value must be defined as an
; absolute path. When this value is not set, chroot is not used.
; Note: chrooting is a great security feature and should be used whenever
;       possible. However, all PHP paths will be relative to the chroot
;       (error_log, sessions.save_path, ...).
; Default Value: not set
;chroot =

; Chdir to this directory at the start.
; Note: relative path can be used.
; Default Value: current directory or / when chroot
;chdir = /var/www

; Redirect worker stdout and stderr into main error log. If not set, stdout and
; stderr will be redirected to /dev/null according to FastCGI specs.
; Note: on highloaded environement, this can cause some delay in the page
; process time (several ms).
; Default Value: no
;catch_workers_output = yes

; Clear environment in FPM workers
; Prevents arbitrary environment variables from reaching FPM worker processes
; by clearing the environment in workers before env vars specified in this
; pool configuration are added.
; Setting to "no" will make all environment variables available to PHP code
; via getenv(), $_ENV and $_SERVER.
; Default Value: yes
;clear_env = no

; Limits the extensions of the main script FPM will allow to parse. This can
; prevent configuration mistakes on the web server side. You should only limit
; FPM to .php extensions to prevent malicious users to use other extensions to
; exectute php code.
; Note: set an empty value to allow all extensions.
; Default Value: .php
;security.limit_extensions = .php .php3 .php4 .php5 .php7

; Pass environment variables like LD_LIBRARY_PATH. All $VARIABLEs are taken from
; the current environment.
; Default Value: clean env
;env[HOSTNAME] = $HOSTNAME
;env[PATH] = /usr/local/bin:/usr/bin:/bin
;env[TMP] = /tmp
;env[TMPDIR] = /tmp
;env[TEMP] = /tmp

; Additional php.ini defines, specific to this pool of workers. These settings
; overwrite the values previously defined in the php.ini. The directives are the
; same as the PHP SAPI:
;   php_value/php_flag             - you can set classic ini defines which can
;                                    be overwritten from PHP call 'ini_set'.
;   php_admin_value/php_admin_flag - these directives won't be overwritten by
;                                     PHP call 'ini_set'
; For php_*flag, valid values are on, off, 1, 0, true, false, yes or no.

; Defining 'extension' will load the corresponding shared extension from
; extension_dir. Defining 'disable_functions' or 'disable_classes' will not
; overwrite previously defined php.ini values, but will append the new value
; instead.

; Default Value: nothing is defined by default except the values in php.ini and
;                specified at startup with the -d argument
;php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i -f [email protected]
;php_flag[display_errors] = off
php_admin_value[error_log] = /var/log/php-fpm/www-error.log
php_admin_flag[log_errors] = on
;php_admin_value[memory_limit] = 128M

; Set session path to a directory owned by process user
php_value[session.save_handler] = files
php_value[session.save_path]    = /var/lib/php/session
php_value[soap.wsdl_cache_dir]  = /var/lib/php/wsdlcache

In my nginx error log I get the repeated message

2018/10/22 22:31:14 [error] 19633#0: *397 recv() failed (104:
Connection reset by peer) while reading response header from upstream,
client: 148.59.205.18, server: www.example.com, request: “GET
/favicon.ico HTTP/1.1”, upstream: “fastcgi://127.0.0.1:9000”, host:
“www.example.com”, referrer: “https://www.example.com/

And in the php-fpm error log I get a large number of errors like the following:

[22-Oct-2018 22:31:14] WARNING: [pool www] child 20134 exited on
signal 6 (SIGABRT) after 0.851864 seconds from start [22-Oct-2018
22:31:14] NOTICE: [pool www] child 20140 started [22-Oct-2018
22:31:14] WARNING: [pool www] child 20135 exited on signal 6 (SIGABRT)
after 0.869394 seconds from start [22-Oct-2018 22:31:14] NOTICE: [pool
www] child 20141 started [22-Oct-2018 22:31:14] WARNING: [pool www]
child 20136 exited on signal 6 (SIGABRT) after 0.870464 seconds from
start

And finally, in /var/log/messages I get

Oct 22 22:18:33 web2 kernel: php-fpm[19710]: segfault at 0 ip 00007f2b9fb553f1 sp 00007ffcce9e3c30 error 6 in libc-2.17.so[7f2b9fad9000+1b8000]

What the heck am I doing wrong? I can’t find anything

My answer:


It looks like you have the apcu extension loaded. This extension has a long history of crash bugs, and I generally recommend disabling it or removing it. If you have a PHP application that depends on it, disable it there as well and check to see if the app supports a different object cache.


View the full question and any other answers on Server Fault.

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