epoll changes are committed to the kernel before epoll_wait() or
on changes array overflow. In the latter case if there are errors
epoll_wait() timeout was not set to zero.
This commit is related to #173 issue on GitHub.
Thanks to 洪志道 (Hong Zhi Dao).
Timers that don't require maximum precision (most of them, actually) can be
triggered earlier or later within the bias interval.
To reduce wakeups by timers, the expire function now triggers not only all
timers that fall within the elapsed time, but also those whose bias falls
within this interval.
Delete/insert operation complexity for a red-black tree is O(log n),
where n is the total number of tree elements.
If all delete operations are performed before all insert operations,
the average number of tree elements during an operation will be
lower than in the mixed-operations case.
To optimize rbtree operations, all changes are stored in array and later
processed in batches.
The previous implementation of this mechanics had a number of design flaws.
Each change was saved in a new array entry; until the changes were applied,
the timer remained in an intermediate state (NXT_TIMER_CHANGING).
This intermediate state didn't allow to identify if time was going to be
disabled or enabled. However, the nxt_conn_io_read() function relied on
this information; as a result, in some cases the read timeout wasn't set.
Also, the nxt_timer_delete() function did not reliably track whether a timer
was added to the work queue. It checked the NXT_TIMER_ENQUEUED state of
a timer, but this state could be reset to NXT_TIMER_DISABLED by a
nxt_timer_disable() call or another nxt_timer_delete() call.
Now, instead of keeping the whole history of the timer's changes, the new
implementation updates the timer state immediately, and only one operation
is added to the array to add or delete timer in the rbtree according
to its final state.
This issue was introduced in libunit commit (e0f0cd7d244a). All port
sockets in application should be in blocking mode whereas Unit itself
operates non-blocking sockets.
Having non-blocking sockets in application may cause send error during
intensive response packets generation.
See https://mailman.nginx.org/pipermail/unit/2018-October/000080.html.
Router requests application start by sending port message with application
parameters to master. In response router gets application port. Stream id
used to link request and response. If application process terminates
unexpectedly (e.g. before ready state), it is required to notify router about
application start failure. For this purpose stream id is stored in process
initialization parameters.
Stream id sequentially incremented and starts from 1 in case of router
resurrection. New router application start stream id may coincide with
stream id of currently running/terminating application processes. In such
cases router may receive REMOVE_PID message with same stream id as used in
application start request and mistakenly reports application start failure.
This commit tries to avoid such errors by resetting stream for processes in
ready state.
Router reconfiguration may lead to starting new application processes, opening
listen ports etc. These actions are asynchronous and require message
exchange with master process. Router stores reference for controller
(response) port in structure associated with reconfiguration process (tmcf).
The port used to provide reconfiguration response (either success or failed)
to controller.
This commit increases response port use counter to make sure port structure
not freed while router waits for result of asynchronous operations.
Previously, passing 0 resulted in reading the whole body and all negative
values raised an exception.
Now the behaviour is in consistentance with io.RawIOBase.read() interface,
and passing 0 returns empty (byte) string, while -1 results in reading the
whole body.
Attribute 'application' is optional in listener object. This commit adds
missing code to reset 'lscf' to avoid garbage and crash when the attribute
is absent.
Unit master process restarts the router if the router accidentally dies.
New router process receives the configuration from controller and starts
configured applications. The information of running applications cannot
be transferred to router because currently there is no persistent application
identifier. To avoid orphan application processes started by died router,
master process stops all currently running applications once it receives
SIGCHLD for router process.
For accurate app descriptor release, it is required to count the number of
use counts. Use count increased when:
- app linked to configuration app queue;
- socket conf stores pointer to app;
- request for start app process posted to router service thread;
Application port has pointer to app, but it does not increase use count
to avoid use count loop.
Timer needs a pointer to nxt_timer_t which is stored in engine timers tree.
nxt_timer_t now resides in nxt_app_joint_t and does not lock the application.
Start process port RPC handlers is also linked to nxt_app_joint_t.
App joint (nxt_app_joint_t) is a 'weak pointer':
- single threaded;
- use countable;
- store pointer to nxt_app_t (which can be NULL);
nxt_app_t has pointer to nxt_app_joint_t and update its pointer to app.
Unit router process may send mmap file decritptor to the application process
for further information exchange. During this process there may be various
errors, which should be described in application error log. If file descriptor
cannot be properly transferred with 'new mmap' message, fd variable will
be assigned to -1 and further syscalls using this file descriptor will fail.
For 'new port' message fd is checked in the same way.
This commit adds early 'invalid file descriptor' diagnostic and write
corresponding message to error log.
Found by Coverity (CID 308515).
For the optimization purpose, function nxt_unit_remove_process() expects
lib->mutex to be locked. The function then moves ports queue into temporary
queue and releases mutex. In nxt_unit_done() there were two errors: mutex was
not locked before nxt_unit_remove_process() call and mutex was not destroyed.
It is hard to tell what was possible negative impact of this errors.
Found by Coverity (CID 308517).
