A prototype stores linked application processes structures. When an
application process terminates, it's removed from the list. To avoid double
removal, the pointer to the next element should be set to NULL.
The issue was introduced in c8790d2a89bb.
Application process started with shared port (and queue) already configured.
But still waits for PORT_ACK message from router to start request processing
(so-called "ready state").
Waiting for router confirmation is necessary. Otherwise, the application may
produce response and send it to router before the router have the information
about the application process. This is a subject of further optimizations.
The default libunit behavior relies on blocking the recv() call for port file
descriptors, which an application may override if needed. For external
applications, port file descriptors were toggled to blocking mode before the
exec() call. If the exec() call failed, descriptor remained blocked, so the
process hanged while trying to read from it.
This patch moves file descriptor mode switch inside libunit.
- Changed the port management callbacks to notifications, which e. g. avoids
the need to call the libunit function
- Added context and library instance reference counts for a safer resource
release
- Added the router main port initialization
Correct value for non-initialized file descriptor is -1, because most of the
checks in libunit compares file descriptor with -1 before performing an
action. Using 0 as default value, may cause to close file descriptor #0, this
may affect application logic.
It is not required to list this patch in changelog because impact is not seen
by end users.
The process abstraction has changed to:
setup(task, process)
start(task, process_data)
prefork(task, process, mp)
The prefork() occurs in the main process right before fork.
The file src/nxt_main_process.c is completely free of process
specific logic.
The creation of a process now supports a PROCESS_CREATED state. The
The setup() function of each process can set its state to either
created or ready. If created, a MSG_PROCESS_CREATED is sent to main
process, where external setup can be done (required for rootfs under
container).
The core processes (discovery, controller and router) doesn't need
external setup, then they all proceeds to their start() function
straight away.
In the case of applications, the load of the module happens at the
process setup() time and The module's init() function has changed
to be the start() of the process.
The module API has changed to:
setup(task, process, conf)
start(task, data)
As a direct benefit of the PROCESS_CREATED message, the clone(2) of
processes using pid namespaces now doesn't need to create a pipe
to make the child block until parent setup uid/gid mappings nor it
needs to receive the child pid.
Changeset #699 fixes shared memory allocation: continous buffer with
requested size should be allocated or function failed. For body longer
than 10 Mb, this allocation will definitely fails.
For body buffer it is not required to send it in a single continous buffer,
so, need to request minimum reasonable amount of shared memory and try to
extend it, if possible or allocate next buffer.
Request <-> application link structure (nxt_req_app_link_t) used to register
the request in application request queue (nxt_app_t.requests) and generate
application-specific port message.
Now it is allocated from request pool. This pool created for request parsing
and used to allocate and store information specific to this request.
The previous attempt of fixing this in e5a65b58101f hasn't been really
successful, because the actual memory leak was caused not by the request
parse context itself, but its memory pool.
