Package ganeti :: Package utils :: Module process

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Module process

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Utility functions for processes.

Classes

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RunResult
Holds the result of running external programs.

Functions

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DisableFork()
Disables the use of fork(2).

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_BuildCmdEnvironment(env, reset)
Builds the environment for an external program.

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RunResult

RunCmd(cmd, env=None, output=None, cwd="/", reset_env=False, interactive=False, timeout=None, noclose_fds=None, input_fd=None, postfork_fn=None)
Execute a (shell) command.

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SetupDaemonEnv(cwd="/", umask=077)
Setup a daemon's environment.

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SetupDaemonFDs(output_file, output_fd)
Setups up a daemon's file descriptors.

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int

StartDaemon(cmd, env=None, cwd="/", output=None, output_fd=None, pidfile=None)
Start a daemon process after forking twice.

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_StartDaemonChild(errpipe_read, errpipe_write, pidpipe_read, pidpipe_write, args, env, cwd, output, fd_output, pidfile)
Child process for starting daemon.

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WriteErrorToFD(fd, err)
Possibly write an error message to a fd.

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_CheckIfAlive(child)
Raises utils_retry.RetryAgain if child is still alive.

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_WaitForProcess(child, timeout)
Waits for the child to terminate or until we reach timeout.

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tuple

_RunCmdPipe(cmd, env, via_shell, cwd, interactive, timeout, noclose_fds, input_fd, postfork_fn=None, _linger_timeout=constants.CHILD_LINGER_TIMEOUT)
Run a command and return its output.

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int

_RunCmdFile(cmd, env, via_shell, output, cwd, noclose_fds)
Run a command and save its output to a file.

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list of tuples

RunParts(dir_name, env=None, reset_env=False)
Run Scripts or programs in a directory

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string

_GetProcStatusPath(pid)
Returns the path for a PID's proc status file.

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boolean

IsProcessAlive(pid)
Check if a given pid exists on the system.

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set

_ParseSigsetT(sigset)
Parse a rendered sigset_t value.

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string

_GetProcStatusField(pstatus, field)
Retrieves a field from the contents of a proc status file.

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bool

IsProcessHandlingSignal(pid, signum, status_path=None)
Checks whether a process is handling a signal.

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tuple; (int, callable)

Daemonize(logfile)
Daemonize the current process.

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KillProcess(pid, signal_=signal.SIGTERM, timeout=30, waitpid=False)
Kill a process given by its pid.

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bool

RunInSeparateProcess(fn, *args)
Runs a function in a separate process.

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CloseFDs(noclose_fds=None)
Close file descriptors.

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Variables

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_no_fork = False
when set to True, RunCmd is disabled

Imports: os, sys, subprocess, errno, select, logging, signal, resource, StringIO, errors, constants, compat, utils_retry, utils_wrapper, utils_text, utils_io, utils_algo

Function Details

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RunCmd(cmd, env=None, output=None, cwd="/", reset_env=False, interactive=False, timeout=None, noclose_fds=None, input_fd=None, postfork_fn=None)

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Execute a (shell) command.

The command should not read from its standard input, as it will be closed.

Parameters:

cmd (string or list) - Command to run
env (dict) - Additional environment variables
output (str) - if desired, the output of the command can be saved in a file instead of the RunResult instance; this parameter denotes the file name (if not None)
cwd (string) - if specified, will be used as the working directory for the command; the default will be /
reset_env (boolean) - whether to reset or keep the default os environment
interactive (boolean) - whether we pipe stdin, stdout and stderr (default behaviour) or run the command interactive
timeout (int) - If not None, timeout in seconds until child process gets killed
noclose_fds (list) - list of additional (fd >=3) file descriptors to leave open for the child process
input_fd (file-like object or numeric file descriptor) - File descriptor for process' standard input
postfork_fn (Callable receiving PID as parameter) - Callback run after fork but before timeout

Returns: RunResult

RunResult instance

Raises:

errors.ProgrammerError - if we call this when forks are disabled

SetupDaemonEnv(cwd="/", umask=077)

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Setup a daemon's environment.

This should be called between the first and second fork, due to setsid usage.

Parameters:

cwd - the directory to which to chdir
umask - the umask to setup

SetupDaemonFDs(output_file, output_fd)

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Setups up a daemon's file descriptors.

Parameters:

output_file - if not None, the file to which to redirect stdout/stderr
output_fd - if not None, the file descriptor for stdout/stderr

StartDaemon(cmd, env=None, cwd="/", output=None, output_fd=None, pidfile=None)

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Start a daemon process after forking twice.

Parameters:

cmd (string or list) - Command to run
env (dict) - Additional environment variables
cwd (string) - Working directory for the program
output (string) - Path to file in which to save the output
output_fd (int) - File descriptor for output
pidfile (string) - Process ID file

Returns: int

Daemon process ID

Raises:

errors.ProgrammerError - if we call this when forks are disabled

WriteErrorToFD(fd, err)

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Possibly write an error message to a fd.

Parameters:

fd (None or int (file descriptor)) - if not None, the error will be written to this fd
err - string, the error message

_CheckIfAlive(child)

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Raises utils_retry.RetryAgain if child is still alive.

Raises:

utils_retry.RetryAgain - If child is still alive

_RunCmdPipe(cmd, env, via_shell, cwd, interactive, timeout, noclose_fds, input_fd, postfork_fn=None, _linger_timeout=constants.CHILD_LINGER_TIMEOUT)

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Run a command and return its output.

Parameters:

cmd (string or list) - Command to run
env (dict) - The environment to use
via_shell (bool) - if we should run via the shell
cwd (string) - the working directory for the program
interactive (boolean) - Run command interactive (without piping)
timeout (int) - Timeout after the programm gets terminated
noclose_fds (list) - list of additional (fd >=3) file descriptors to leave open for the child process
input_fd (file-like object or numeric file descriptor) - File descriptor for process' standard input
postfork_fn (Callable receiving PID as parameter) - Function run after fork but before timeout

Returns: tuple

(out, err, status)

_RunCmdFile(cmd, env, via_shell, output, cwd, noclose_fds)

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Run a command and save its output to a file.

Parameters:

cmd (string or list) - Command to run
env (dict) - The environment to use
via_shell (bool) - if we should run via the shell
output (str) - the filename in which to save the output
cwd (string) - the working directory for the program
noclose_fds (list) - list of additional (fd >=3) file descriptors to leave open for the child process

Returns: int

the exit status

RunParts(dir_name, env=None, reset_env=False)

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Run Scripts or programs in a directory

Parameters:

dir_name (string) - absolute path to a directory
env (dict) - The environment to use
reset_env (boolean) - whether to reset or keep the default os environment

Returns: list of tuples

list of (name, (one of RUNDIR_STATUS), RunResult)

_GetProcStatusPath(pid)

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Returns the path for a PID's proc status file.

Parameters:

pid (int) - Process ID

Returns: string

IsProcessAlive(pid)

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Check if a given pid exists on the system.

Parameters:

pid (int) - the process ID to check

Returns: boolean

True if the process exists

Note: zombie status is not handled, so zombie processes will be returned as alive

_ParseSigsetT(sigset)

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Parse a rendered sigset_t value.

This is the opposite of the Linux kernel's fs/proc/array.c:render_sigset_t function.

Parameters:

sigset (string) - Rendered signal set from /proc/$pid/status

Returns: set

Set of all enabled signal numbers

_GetProcStatusField(pstatus, field)

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Retrieves a field from the contents of a proc status file.

Parameters:

pstatus (string) - Contents of /proc/$pid/status
field (string) - Name of field whose value should be returned

Returns: string

IsProcessHandlingSignal(pid, signum, status_path=None)

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Checks whether a process is handling a signal.

Parameters:

pid (int) - Process ID
signum (int) - Signal number

Returns: bool

Daemonize(logfile)

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Daemonize the current process.

This detaches the current process from the controlling terminal and runs it in the background as a daemon.

Parameters:

logfile (str) - the logfile to which we should redirect stdout/stderr

Returns: tuple; (int, callable)

File descriptor of pipe(2) which must be closed to notify parent process and a callable to reopen log files

KillProcess(pid, signal_=signal.SIGTERM, timeout=30, waitpid=False)

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Kill a process given by its pid.

Parameters:

pid (int) - The PID to terminate.
signal_ (int) - The signal to send, by default SIGTERM
timeout (int) - The timeout after which, if the process is still alive, a SIGKILL will be sent. If not positive, no such checking will be done
waitpid (boolean) - If true, we should waitpid on this process after sending signals, since it's our own child and otherwise it would remain as zombie

RunInSeparateProcess(fn, *args)

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Runs a function in a separate process.

Note: Only boolean return values are supported.

Parameters:

fn (callable) - Function to be called

Returns: bool

Function's result

CloseFDs(noclose_fds=None)

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Close file descriptors.

This closes all file descriptors above 2 (i.e. except stdin/out/err).

Parameters:

noclose_fds (list or None) - if given, it denotes a list of file descriptor that should not be closed