Create another thread to watch over the daemon process and
automatically shut it down if necessary.
This commit creates the basic framework for a "health" thread
to monitor the daemon and/or the file system. Later commits
will add platform-specific code to do the actual work.
The "health" thread is intended to monitor conditions that
would be difficult to track inside the IPC thread pool and/or
the file system listener threads. For example, when there are
file system events outside of the watched worktree root or if
we want to have an idle-timeout auto-shutdown feature.
This commit creates the health thread itself, defines the thread-proc
and sets up the thread's event loop. It integrates this new thread
into the existing IPC and Listener thread models.
This commit defines the API to the platform-specific code where all of
the monitoring will actually happen.
The platform-specific code for MacOS is just stubs. Meaning that the
health thread will immediately exit on MacOS, but that is OK and
expected. Future work can define MacOS-specific monitoring.
The platform-specific code for Windows sets up enough of the
WaitForMultipleObjects() machinery to watch for system and/or custom
events. Currently, the set of wait handles only includes our custom
shutdown event (sent from our other theads). Later commits in this
series will extend the set of wait handles to monitor other
conditions.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Rename platform-specific listener thread related variables
and data types as we prepare to add another backend thread
type.
[] `struct fsmonitor_daemon_backend_data` becomes `struct fsm_listen_data`
[] `state->backend_data` becomes `state->listen_data`
[] `state->error_code` becomes `state->listen_error_code`
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Refactor daemon thread startup to make it easier to start
a third thread class to monitor the health of the daemon.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach the fsmonitor--daemon to CD outside of the worktree
before starting up.
The common Git startup mechanism causes the CWD of the daemon process
to be in the root of the worktree. On Windows, this causes the daemon
process to hold a locked handle on the CWD and prevents other
processes from moving or deleting the worktree while the daemon is
running.
CD to HOME before entering main event loops.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Bare repos do not have a worktree, so there is nothing for the
daemon watch.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach fsmonitor--daemon client threads to create a cookie file
inside the .git directory and then wait until FS events for the
cookie are observed by the FS listener thread.
This helps address the racy nature of file system events by
blocking the client response until the kernel has drained any
event backlog.
This is especially important on MacOS where kernel events are
only issued with a limited frequency. See the `latency` argument
of `FSeventStreamCreate()`. The kernel only signals every `latency`
seconds, but does not guarantee that the kernel queue is completely
drained, so we may have to wait more than one interval. If we
increase the latency, the system is more likely to drop events.
We avoid these issues by having each client thread create a unique
cookie file and then wait until it is seen in the event stream.
Co-authored-by: Kevin Willford <Kevin.Willford@microsoft.com>
Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach fsmonitor--daemon to periodically truncate the list of
modified files to save some memory.
Clients will ask for the set of changes relative to a token that they
found in the FSMN index extension in the index. (This token is like a
point in time, but different). Clients will then update the index to
contain the response token (so that subsequent commands will be
relative to this new token).
Therefore, the daemon can gradually truncate the in-memory list of
changed paths as they become obsolete (older than the previous token).
Since we may have multiple clients making concurrent requests with a
skew of tokens and clients may be racing to the talk to the daemon,
we lazily truncate the list.
We introduce a 5 minute delay and truncate batches 5 minutes after
they are considered obsolete.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach fsmonitor--daemon to respond to IPC requests from client
Git processes and respond with a list of modified pathnames
relative to the provided token.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach fsmonitor--daemon to build a list of changed paths and associate
them with a token-id. This will be used by the platform-specific
backends to accumulate changed paths in response to filesystem events.
The platform-specific file system listener thread receives file system
events containing one or more changed pathnames (with whatever
bucketing or grouping that is convenient for the file system). These
paths are accumulated (without locking) by the file system layer into
a `fsmonitor_batch`.
When the file system layer has drained the kernel event queue, it will
"publish" them to our token queue and make them visible to concurrent
client worker threads. The token layer is free to combine and/or de-dup
paths within these batches for efficient presentation to clients.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach fsmonitor--daemon to create token-ids and define the
overall token naming scheme.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach fsmonitor--daemon to classify relative and absolute
pathnames and decide how they should be handled. This will
be used by the platform-specific backend to respond to each
filesystem event.
When we register for filesystem notifications on a directory,
we get events for everything (recursively) in the directory.
We want to report to clients changes to tracked and untracked
paths within the working directory proper. We do not want to
report changes within the .git directory, for example.
This classification will be used in a later commit by the
different backends to classify paths as events are received.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Implement 'git fsmonitor--daemon start' command. This command starts
an instance of 'git fsmonitor--daemon run' in the background using
the new 'start_bg_command()' function.
We avoid the fork-and-call technique on Unix systems in favor of a
fork-and-exec technique. This gives us more uniform Trace2 child-*
events. It also makes our usage more consistent with Windows usage.
On Windows, teach 'git fsmonitor--daemon run' to optionally call
'FreeConsole()' to release handles to the inherited Win32 console
(despite being passed invalid handles for stdin/out/err). Without
this, command prompts and powershell terminal windows could hang
in "exit" until the last background child process exited or released
their Win32 console handle. (This was not seen with git-bash shells
because they don't have a Win32 console attached to them.)
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Implement `run` command to try to begin listening for file system events.
This version defines the thread structure with a single fsmonitor_fs_listen
thread to watch for file system events and a simple IPC thread pool to
watch for connection from Git clients over a well-known named pipe or
Unix domain socket.
This commit does not actually do anything yet because the platform
backends are still just stubs.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Implement `stop` and `status` client commands to control and query the
status of a `fsmonitor--daemon` server process (and implicitly start a
server process if necessary).
Later commits will implement the actual server and monitor the file
system.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Create a built-in file system monitoring daemon that can be used by
the existing `fsmonitor` feature (protocol API and index extension)
to improve the performance of various Git commands, such as `status`.
The `fsmonitor--daemon` feature builds upon the `Simple IPC` API and
provides an alternative to hook access to existing fsmonitors such
as `watchman`.
This commit merely adds the new command without any functionality.
Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
