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Dev: Allow to delay main worker process in order to attach with LLDB 

Introduce `-DInternal.DebugWorkerDelay=120` and sleep inside `RunWorker()`.

Rationale: With 2.11 we've introduced a real umbrella process where the
main process is spawned as child fork. Running icinga2 in foreground on
a macOS shell with LLDB will now exit, and not follow the child process.

LLDB doesn't support `follow-fork-mode child` like GDB and therefore we
need to:

- Print the child process PID
- Sleep for X seconds to allow the developer to run `lldb -p <PID>`, set breakpoints, etc.

This commit also documents all available debug build enabled internal constants.
This commit is contained in:
Michael Friedrich 2020-01-29 12:38:12 +01:00
parent fe8701d77e
commit 5812dae55b
2 changed files with 52 additions and 0 deletions
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22
doc/17-language-reference.md
View File

@ -566,6 +566,28 @@ ICINGA2\_RLIMIT\_FILES |**Read-write.** Defines the resource limit for `RLIM
ICINGA2\_RLIMIT\_PROCESSES |**Read-write.** Defines the resource limit for `RLIMIT_NPROC` that should be set at start-up. Value cannot be set lower than the default `16 * 1024`. 0 disables the setting. Set in Icinga 2 sysconfig.
ICINGA2\_RLIMIT\_STACK |**Read-write.** Defines the resource limit for `RLIMIT_STACK` that should be set at start-up. Value cannot be set lower than the default `256 * 1024`. 0 disables the setting. Set in Icinga 2 sysconfig.
#### Debug Constants and Variables <a id="icinga-constants-debug"></a>
These constants are only available in debug builds for developers and help with tracing messages and attaching to debuggers.
Variable | Description
---------------------------|-------------------
Internal.DebugJsonRpc | **Read-write.** Setting this to `1` prints the raw JSON-RPC message to STDOUT.
Internal.DebugWorkerDelay | **Read-write.** Delays the main worker process by X seconds after forked from the umbrella process. This helps with attaching LLDB which cannot follow child forks like GDB.
Example:
```
$ icinga2 daemon -DInternal.DebugWorkerDelay=120
Closed FD 6 which we inherited from our parent process.
[2020-01-29 12:22:33 +0100] information/cli: Icinga application loader (version: v2.11.0-477-gfe8701d77; debug)
[2020-01-29 12:22:33 +0100] information/RunWorker: DEBUG: Current PID: 85253. Sleeping for 120 seconds to allow lldb/gdb -p <PID> attachment.
$ lldb -p 85253
(lldb) b icinga::Checkable::ProcessCheckResult
(lldb) c
```
## Apply <a id="apply"></a>

30
lib/cli/daemoncommand.cpp
View File

@ -191,6 +191,24 @@ pid_t l_UmbrellaPid = 0;
static Atomic<bool> l_AllowedToWork (false);
#endif /* _WIN32 */
#ifdef I2_DEBUG
/**
* Determine whether the developer wants to delay the worker process to attach a debugger to it.
*
* @return Internal.DebugWorkerDelay double
*/
static double GetDebugWorkerDelay()
{
Namespace::Ptr internal = ScriptGlobal::Get("Internal", &Empty);
Value vdebug;
if (internal && internal->Get("DebugWorkerDelay", &vdebug))
return Convert::ToDouble(vdebug);
return 0.0;
}
#endif /* I2_DEBUG */
/**
* Do the actual work (config loading, ...)
*
@ -203,6 +221,18 @@ static Atomic<bool> l_AllowedToWork (false);
static inline
int RunWorker(const std::vector<std::string>& configs, bool closeConsoleLog = false, const String& stderrFile = String())
{
#ifdef I2_DEBUG
double delay = GetDebugWorkerDelay();
if (delay > 0.0) {
Log(LogInformation, "RunWorker")
<< "DEBUG: Current PID: " << Utility::GetPid() << ". Sleeping for " << delay << " seconds to allow lldb/gdb -p <PID> attachment.";
Utility::Sleep(delay);
}
#endif /* I2_DEBUG */
Log(LogInformation, "cli", "Loading configuration file(s).");
{