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MXS-1405: Execute EXTERNCMD synchronously

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The execution of external commands in MaxScale by monitors needs to be
synchronous in order to prevent the unintended detection of state changes.
This commit is contained in:
Markus Mäkelä
2017-09-13 22:47:58 +03:00
parent efb1e541e2
commit 4f7606ebc0
3 changed files with 71 additions and 49 deletions
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67
server/core/externcmd.cc
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@ -16,10 +16,12 @@
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <sys/wait.h>
#include <maxscale/alloc.h>
#include <maxscale/log_manager.h>
#include <maxscale/pcre2.h>
#include <maxscale/thread.h>
@ -175,6 +177,7 @@ int externcmd_execute(EXTERNCMD* cmd)
int rval = 0;
pid_t pid;
// The SIGCHLD handler must be disabled before child process is forked
pid = fork();
if (pid < 0)
@ -191,9 +194,71 @@ int externcmd_execute(EXTERNCMD* cmd)
}
else
{
MXS_INFO("Executing command '%s' in process %d", cmd->argv[0], pid);
cmd->child = pid;
cmd->n_exec++;
MXS_DEBUG("[monitor_exec_cmd] Forked child process %d : %s.", pid, cmd->argv[0]);
bool first_warning = true;
bool again = true;
uint64_t t = 0;
uint64_t t_max = cmd->timeout * 1000;
while (again)
{
int exit_status;
switch (waitpid(pid, &exit_status, WNOHANG))
{
case -1:
MXS_ERROR("Failed to wait for child process: %d, %s", errno, mxs_strerror(errno));
again = false;
break;
case 0:
if (t++ > t_max)
{
// Command timed out
t = 0;
if (first_warning)
{
MXS_WARNING("Soft timeout for command '%s', sending SIGTERM", cmd->argv[0]);
kill(pid, SIGTERM);
first_warning = false;
}
else
{
MXS_ERROR("Hard timeout for command '%s', sending SIGKILL", cmd->argv[0]);
kill(pid, SIGKILL);
}
}
else
{
// Sleep and try again
thread_millisleep(1);
}
break;
default:
again = false;
if (WIFEXITED(exit_status))
{
rval = WEXITSTATUS(exit_status);
}
else if (WIFSIGNALED(exit_status))
{
rval = WTERMSIG(exit_status);
}
else
{
rval = exit_status;
MXS_ERROR("Command '%s' did not exit normally. Exit status: %d",
cmd->argv[0], exit_status);
}
break;
}
}
}
return rval;