Introducing application prototype processes.

Changed nxt_process_* for reuse.

This enables the reuse of process creation functions.

Introduced SCM_CREDENTIALS / SCM_CREDS in the socket control msgs.

Moving request limit control to libunit.

Introducting application graceful stop. For now only used when application
process reach request limit value.

This closes #585 issue on GitHub.

Application restart introduced.

When processing a restart request, the router sends a QUIT message to all
existing processes of the application. Then, a new shared application port is
created to en

Application restart introduced.

When processing a restart request, the router sends a QUIT message to all
existing processes of the application. Then, a new shared application port is
created to ensure that new requests won't be handled by the old processes of
the application.

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Router: introducing the PORT_ACK message.

The PORT_ACK message is the router's response to the application's NEW_PORT
message. After receiving PORT_ACK, the application is safe to process requests

Router: introducing the PORT_ACK message.

The PORT_ACK message is the router's response to the application's NEW_PORT
message. After receiving PORT_ACK, the application is safe to process requests
using this port.

This message avoids a racing condition when the application starts processing a
request from the shared queue and sends REQ_HEADERS_ACK. The REQ_HEADERS_ACK
message contains the application port ID as reply_port, which the router uses
to send request data. When the application creates a new port, it
immediately sends it to the main router thread. Because the request is
processed outside the main thread, a racing condition can occur between the
receipt of the new port in the main thread and the receipt of REQ_HEADERS_ACK
in the worker router thread where the same port is specified as reply_port.

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Style fixes for 2 file descriptors transfer over port.

Two consecutive fd and fd2 fields replaced with array.

Introducing application and port shared memory queues.

The goal is to minimize the number of syscalls needed to deliver a message.

Port message extended to transfer 2 file descriptors.

Introducing the shared application port.

This is the port shared between all application processes which use it to pass
requests for processing. Using it significantly simplifies the request
proces

Introducing the shared application port.

This is the port shared between all application processes which use it to pass
requests for processing. Using it significantly simplifies the request
processing code in the router. The drawback is 2 more file descriptors per each
configured application and more complex libunit message wait/read code.

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Changing router to application shared memory exchange protocol.

The application process needs to request the shared memory segment from the
router instead of the latter pushing the segment before se

Changing router to application shared memory exchange protocol.

The application process needs to request the shared memory segment from the
router instead of the latter pushing the segment before sending a request to
the application. This is required to simplify the communication between the
router and the application and to prepare the router for using the application
shared port and then the queue.

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Changing router to application port exchange protocol.

The application process needs to request the port from the router instead of the
latter pushing the port before sending a request to the applic

Changing router to application port exchange protocol.

The application process needs to request the port from the router instead of the
latter pushing the port before sending a request to the application. This is
required to simplify the communication between the router and the application
and to prepare the router to use the application shared port and then the queue.

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Refactor of process management.

The process abstraction has changed to:

setup(task, process)
start(task, process_data)
prefork(task, process, mp)

The prefork() occurs in the main process rig

Refactor of process management.

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.

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Introducing port messages to notify about out of shared memory.

- OOSM (out of shared memory). Sent by application process to router
when application reaches the limit of allocated shared memory

Introducing port messages to notify about out of shared memory.

- OOSM (out of shared memory). Sent by application process to router
when application reaches the limit of allocated shared memory and
needs more.
- SHM_ACK. Sent by router to application when the application's shared
memory is released and the OOSM flag is enabled for the segment.

This implements blocking mode (the library waits for SHM_ACK in case of
out of shared memory condition and retries allocating the required memory
amount) and non-blocking mode (the library notifies the application that
it's out of shared memory and returns control to the application module
that sets up the output queue and puts SHM_ACK in the main message loop).

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Refactor of process init.

Introduces the functions nxt_process_init_create() and
nxt_process_init_creds_set().

Introducing websocket support in router and libunit.

Fixing multi-thread port write racing conditions.

Controller: certificates storage interface.

Initial access log support.

Style.

Introducing extended app process management.

- Pre-fork 'processes.spare' application processes;
- fork more processes to keep 'processes.spare' idle processes;
- fork on-demand up to 'processes.max

Introducing extended app process management.

- Pre-fork 'processes.spare' application processes;
- fork more processes to keep 'processes.spare' idle processes;
- fork on-demand up to 'processes.max' count;
- scale down idle application processes above 'processes.spare' after
'processes.idle_timeout';
- number of concurrently started application processes also limited by
'processes.spare' (or 1, if spare is 0).

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Fixing application timeout.

Application timeout limits maximum time of worker response in processing
particular request. Not including the time required to start worker,
time in request queue etc.

Changing worker selection precedence.

This patch increase precedence of non-started worker over busy worker.

1. idle worker;
2. start new worker;
3. busy worker, but can accept request in advance;

Implementing the ability to cancel request before worker starts processing it.

Fixing build on Solaris.