bitcoind: Daemonize using daemon(3)

laanwj commented at 9:39 am on September 26, 2016: member

Simplified version of #8278. Assumes that every OS that (a) is supported by Bitcoin Core (b) supports daemonization has the daemon() function in its C library.

Removes the fallback path for operating systems that support daemonization but not daemon(). This prevents never-exercised code from ending up in the repository (see discussion here: #8278 (comment)).
Removes the windows-specific path. Windows doesn’t support daemon(), so it doesn’t support daemonization there, automatically. Give an explicit error if a user specifies -daemon on an OS where this is not supported.
Also made showing the help message depend on HAVE_DECL_DAEMON instead of !WIN32.

The original problem reported in #8278 was “When started with cron, the sendmail process hung around waiting for its stdin, bitcoind’s stdout/err, to close..”.

laanwj added the label Utils and libraries on Sep 26, 2016

in src/bitcoind.cpp: in 365c2d9fea outdated

137             // Daemonize
138-            pid_t pid = fork();
139-            if (pid < 0)
140-            {
141-                fprintf(stderr, "Error: fork() returned %d errno %d\n", pid, errno);
142+            // daemon(3) basically does exactly what follows in the else block,

sipa commented at 9:44 am on September 26, 2016:

That’s not true anymore.

laanwj commented at 9:45 am on September 26, 2016:

Two more lines that can be deleted, thanks.

laanwj force-pushed on Sep 26, 2016

laanwj renamed this:
~~bitcoind: Daemonise using daemon(3)~~
bitcoind: Daemonize using daemon(3)
on Sep 26, 2016

bitcoind: Daemonize using daemon(3)

Simplified version of #8278. Assumes that every OS that (a) is supported
by Bitcoin Core (b) supports daemonization has the `daemon()` function
in its C library.

- Removes the fallback path for operating systems that support
  daemonization but not `daemon()`. This prevents never-exercised code from
  ending up in the repository (see discussion here:
  https://github.com/bitcoin/bitcoin/pull/8278#issuecomment-242704745).

- Removes the windows-specific path. Windows doesn't support `daemon()`,
  so it don't support daemonization there, automatically.

Original code by Matthew King, adapted by Wladimir van der Laan.

a92bf4af66

laanwj force-pushed on Sep 26, 2016

jonasschnelli approved

jonasschnelli commented at 11:53 am on September 26, 2016: contributor

utACK https://github.com/bitcoin/bitcoin/pull/8813/commits/a92bf4af66f8b5a2e6bc28baa6670065ce76daf2 (-comment nit mentioned by @sipa)

jonasschnelli commented at 2:10 pm on September 26, 2016: contributor

Tested ACK (OSX) https://github.com/bitcoin/bitcoin/pull/8813/commits/a92bf4af66f8b5a2e6bc28baa6670065ce76daf2. Binaries: https://bitcoin.jonasschnelli.ch/pulls/8813/

MarcoFalke commented at 8:22 pm on September 27, 2016: member

Possibly related: #4676 (haven’t checked)

sipa commented at 0:20 am on September 28, 2016: member

Concept ACK.

laanwj commented at 7:18 am on September 28, 2016: member

Possibly related: #4676 (haven’t checked)

Yes, using daemonize() seems quite a step closer to standard UNIX daemon practices. Though we had to decide in #8278 to use the nochdir flag as, without further changes, it would have effects on option behavior.

laanwj merged this on Sep 30, 2016

laanwj closed this on Sep 30, 2016

laanwj referenced this in commit fb24d7eeb4 on Sep 30, 2016

laanwj commented at 4:21 pm on September 30, 2016: member

Note: if you end up here seeing the “Error: -daemon is not supported on this operating system” message while your OS does support it, this most likely means you need to re-run autogen.sh and configure.

paveljanik commented at 8:59 pm on October 21, 2016: contributor

This brings new warning on OS X:

0bitcoind.cpp:137:17: warning: 'daemon' is deprecated: first deprecated in OS X 10.5 [-Wdeprecated-declarations]
1            if (daemon(1, 0)) {
2                ^
3/usr/include/stdlib.h:267:5: note: 'daemon' has been explicitly marked deprecated here
4int daemon(int, int) __asm("_" "daemon" "$1050") __attribute__((availability(macosx,introduced=10.0,deprecated=10.5)));
5    ^
61 warning generated.

laanwj commented at 7:27 am on October 22, 2016: member

You can’t be friggin serious. I’m going to revert this - it’s only causing trouble.

laanwj commented at 7:27 am on October 22, 2016: member

@paveljanik Just curious do they suggest anything to use instead of daemon?

jonasschnelli commented at 7:43 am on October 22, 2016: contributor

I wouldn’t take the deprecation warning to serious. OSX want devs to use its own launchd/launchctrl. Removing the actual daemon() systemcall would break tons of applications and if - we would have at least 1-2 years to switch to launchd on OSX.

laanwj commented at 7:43 am on October 22, 2016: member

Apparently they recommend doing something Apple-specific with plists and such https://developer.apple.com/library/content/technotes/tn2083/_index.html#//%20apple_ref/doc/uid/DTS10003794-CH1-SUBSECTION64 Bah. Okay, reverting this isn’t any help either then. Never mind that. I got upset.

paveljanik commented at 8:15 am on October 22, 2016: contributor

I agree with @jonasschnelli. No need to revert this. This only shows how Apple deprecates stuff. 10.5. Deprecated since October 26, 2007, still works now ;-)

What is the current status of daemon in the current macOS?

luke-jr referenced this in commit 377ab84465 on Dec 21, 2016

codablock referenced this in commit e9bf59fb07 on Sep 19, 2017

codablock referenced this in commit 210242e5c0 on Jan 12, 2018

andvgal referenced this in commit 88c4a0abd3 on Jan 6, 2019

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bitcoind: Daemonize using daemon(3) #8813