It allows proceeding to another action if a file isn't available.
An example:
{
"share": "/data/www/",
"fallback": {
"pass": "applications/php"
}
}
In the example above, an attempt is made first to serve a request with
a file from the "/data/www/" directory. If there's no such file, the
request is passed to the "php" application.
Fallback actions may be nested:
{
"share": "/data/www/",
"fallback": {
"share": "/data/cache/",
"fallback": {
"proxy": "http://127.0.0.1:9000"
}
}
}
For each request, the worker calls the php_execute_script function
from libphp that changes to the script directory before doing its
work and then restores the process directory before returning. The
chdir(2) calls it performs are unnecessary in Unit design. In simple
benchmarks, profiling shows that the chdir syscall code path (syscall,
FS walk, etc.) is where the CPU spends most of its time.
PHP SAPI semantics requires the script to be run from the script
directory. In Unit's PHP implementation, we have two use cases:
- script
- arbitrary path
The "script" configuration doesn't have much need for a working
directory change: it can be changed once at module initialization.
The module needs to chdir again only if the user's PHP script also
calls chdir to switch to another directory during execution.
If "script" is not used in Unit configuration, we must ensure the
script is run from its directory (thus calling chdir before exec),
but there's no need to restore the working directory later.
Our implementation disables mandatory chdir calls with the SAPI
option SAPI_OPTION_NO_CHDIR, instead calling chdir only when needed.
To detect the user's calls to chdir, a simple "unit" extension is
added that hooks the built-in chdir() PHP call.
Router built with debug may stop with assertion during stalled requests
re-schedule. This was caused by missing reference counting increment
before nxt_router_port_select() call.
Uninitialized ctx_impl field may cause crash in application process.
To reproduce the issue, need to trigger shared memory buffer send error on
application side. In our case, send error caused by router process crash.
This issue was introduced in 2c7f79bf0a1f.
Re-scheduled req_app_link structures should have use_count exactly equal
to the number of references from the application and port list. However,
there's one extra usage decrement that occurs after the req_app_link is
created because the use_count is initialised as 1.
This patch removes all excess instances of the usage decrement that caused
preliminary req_app_link release and router process crash.
To reproduce the issue need to cause request rescheduling between 2 app
processes.
This issue was introduced in 61e9f23a566d.
A check for the ".php" extension is added to prevent execution of files
with arbitrary extensions in cases where "index" and "script" options
aren't used.
For backward compatibility, the Linux capabilities macros exposes v1 semantics
(32-bit) by default. We probe the version at runtime (because of pre-compiled
binaries) but the kernel syscall API is conservative and it doesn't return a
64-bit capability version if the input version is v1.
This patch suppress the kernel > 5.0 dmesg log below:
capability: warning: 'unitd' uses 32-bit capabilities (legacy support in use)
ServerResponse.write() method tries to write data buffer using libunit
and stores buffers to write in a Server-wide output queue, which is
processed in response to SHM_ACK message from router.
As a side effect 'drain' event implemented and socket.writable flag
reflect current state.
- 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).
Current shared memory buffer implementation uses fixed-size memory blocks,
allocating at least 16384 bytes. When application sends data in a large
number of small chunks, it makes sense to buffer them or use plain
memory buffers to improve performance and reduce memory footprint.
This patch introduces minimum size limit (1024 bytes) for shared
memory buffers.
The setuid/setgid syscalls requires root capabilities but if the kernel
supports unprivileged user namespace then the child process has the full
set of capabilities in the new namespace, then we can allow setting "user"
and "group" in such cases (this is a common security use case).
Tests were added to ensure user gets meaningful error messages for
uid/gid mapping misconfigurations.
This is required to avoid include cycles, as some nxt_clone_* functions
depend on the credential structures, but nxt_process depends on clone
structures.
Now the nxt_user_groups_get() function uses getgrouplist(3) when available
(except MacOS, see below). For some platforms, getgrouplist() supports
a method of probing how much groups the user has but the behavior is not
consistent. The method used here consists of optimistically trying to get up
to min(256, NGROUPS_MAX) groups; only if ngroups returned exceeds the original
value, we do a second call. This method can block main's process if LDAP/NDIS+
is in use.
MacOS has getgrouplist(3) but it's buggy. It doesn't update ngroups if the
value passed is smaller than the number of groups the user has. Some
projects (like Go stdlib) call getgrouplist() in a loop, increasing ngroups
until it exceeds the number of groups user belongs to or fail when a limit
is reached. For performance reasons, this is to be avoided and MacOS is
handled in the fallback implementation.
The fallback implementation is the old Unit approach. It saves main's
user groups (getgroups(2)) and then calls initgroups(3) to load application's
groups in main, then does a second getgroups(2) to store the gids and restore
main's groups in the end. Because of initgroups(3)' call to setgroups(2),
this method requires root capabilities. In the case of OSX, which has
small NGROUPS_MAX by default (16), it's not possible to restore main's groups
if it's large; if so, this method fallbacks again: user_cred gids aren't
stored, and the worker process calls initgroups() itself and may block for
some time if LDAP/NDIS+ is in use.
The reason for the change is that the req_app_link reference count
was incorrect if the application crashed at start; in this case,
the nxt_request_app_link_update_peer() function was never called.
This closes#332 issue on GitHub.
A quote from the Python 3 documentation:
| When interactive, stdout and stderr streams are line-buffered.
| Otherwise, they are block-buffered like regular text files.
As a result, if an exception occurred and PyErr_Print() was called, its output
could be buffered but not printed to the log for a while (ultimately, until
the interpreter finalization). If the application process crashed shortly,
the backtrace was completely lost.
Buffering can be disabled by redefining the sys.stderr stream object.
However, interference with standard environment objects was deemed undesirable.
Instead, sys.stderr.flush() is called every time after printing exceptions.
A potential advantage here is that lines from backtraces won't be mixed
with other lines in the log.
PyObject_HasAttrString() is just a wrapper over PyObject_GetAttrString(),
while PyObject_CallMethod() calls it as the first step. As a result,
PyObject_GetAttrString() was called twice if close() was present.
To get rid of PyObject_HasAttrString() while keeping the same behaviour,
the PyObject_CallMethod() call has been decomposed into separate calls of
PyObject_GetAttrString() and PyObject_CallFunction().
On success, PyObject_CallMethod() returns a new reference to
the result of the call, which previously got lost.
Also, error logging on failure was added.
The issue was introduced by b0148ec28c4d.
According to the documentation, PyObject_GetIter():
| Raises TypeError and returns NULL if the object cannot be iterated.
Previously, this exception wasn't printed or cleared and remained unhandled.
According to the documentation, PyIter_Next():
| If there are no remaining values, returns NULL with no exception set.
| If an error occurs while retrieving the item, returns NULL and passes
| along the exception.
Previously, this exception wasn't properly handled and the response was
finalized as successful.
This issue was introduced in b0148ec28c4d.
A check for PyErr_Occurred() located in the code below might print this
traceback or occasionally catch an exception from one of the two response
close() calls.
Albeit that exceptions from the close() calls also need to be catched,
it's clear that this particular check wasn't supposed to do so. This is
another issue and it will be fixed later.
