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package/apache: atomic creation of pid file.

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The original pattern for creating the pid file was:
open_create(pid_file)
write(pid_file, pid)
close(pid_file)

But if a power outage occurs between open_create and write, the file will
be empty and httpd will refuse to start afterwards unless the corrupt pid
file is removed.

This patch uses the pattern:
open_create(temp_pid_file)
write(temp_pid_file)
close(temp_pid_file)
rename(temp_pid_file, pid_file)
which is guaranteed to be atomic, provided that temp_pid_file and pid_file
are located in the same file system, which this patch does by creating
a temporary file name with the pattern:
    pid_file_name + random_suffix

Patch is upstream as of
dd10a9352e,
which will be in the next 2.5.x version.

Signed-off-by: Nicolas Carrier <nicolas.carrier@orolia.com>
[Thomas: update to use upstreamed patch.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
This commit is contained in:
Nicolas Carrier 2019-09-23 07:47:27 +00:00 committed by Thomas Petazzoni
parent 5234acc639
commit 67fbb903b6
1 changed files with 77 additions and 0 deletions
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77
package/apache/0004-server-log.c-ap_log_pid-Use-a-temporary-file-then-re.patch Normal file
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@ -0,0 +1,77 @@
From 5b95d256387b45fbe33f7ee7890ae35afdd5c371 Mon Sep 17 00:00:00 2001
From: Joe Orton <jorton@apache.org>
Date: Fri, 13 Mar 2020 14:34:18 +0000
Subject: [PATCH] * server/log.c (ap_log_pid): Use a temporary file, then
rename once successfully written; also add error checking. Avoids startup
failures if a previous httpd invocation crashed while writing the pidfile.
Submitted by: Nicolas Carrier <carrier.nicolas0 gmail.com>, jorton
Github: closes #100, closes #69
PR: 63140
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1875153 13f79535-47bb-0310-9956-ffa450edef68
Signed-off-by: Nicolas Carrier <nicolas.carrier@orolia.com>
---
server/log.c | 33 ++++++++++++++++++++++++++-------
1 file changed, 26 insertions(+), 7 deletions(-)
diff --git a/server/log.c b/server/log.c
index f0bde6e4b8..8d54b4e057 100644
--- a/server/log.c
+++ b/server/log.c
@@ -1598,6 +1598,9 @@ AP_DECLARE(void) ap_log_pid(apr_pool_t *p, const char *filename)
pid_t mypid;
apr_status_t rv;
const char *fname;
+ char *temp_fname;
+ apr_fileperms_t perms;
+ char pidstr[64];
if (!filename) {
return;
@@ -1626,19 +1629,35 @@ AP_DECLARE(void) ap_log_pid(apr_pool_t *p, const char *filename)
fname);
}
- if ((rv = apr_file_open(&pid_file, fname,
- APR_WRITE | APR_CREATE | APR_TRUNCATE,
- APR_UREAD | APR_UWRITE | APR_GREAD | APR_WREAD, p))
- != APR_SUCCESS) {
+ temp_fname = apr_pstrcat(p, fname, ".XXXXXX", NULL);
+ rv = apr_file_mktemp(&pid_file, temp_fname,
+ APR_FOPEN_WRITE | APR_FOPEN_CREATE | APR_FOPEN_TRUNCATE, p);
+ if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ERR, rv, NULL, APLOGNO(00099)
- "could not create %s", fname);
+ "could not create %s", temp_fname);
ap_log_error(APLOG_MARK, APLOG_ERR, 0, NULL, APLOGNO(00100)
"%s: could not log pid to file %s",
ap_server_argv0, fname);
exit(1);
}
- apr_file_printf(pid_file, "%" APR_PID_T_FMT APR_EOL_STR, mypid);
- apr_file_close(pid_file);
+
+ apr_snprintf(pidstr, sizeof pidstr, "%" APR_PID_T_FMT APR_EOL_STR, mypid);
+
+ perms = APR_UREAD | APR_UWRITE | APR_GREAD | APR_WREAD;
+ rv = apr_file_perms_set(temp_fname, perms);
+ if (rv == APR_SUCCESS)
+ rv = apr_file_write_full(pid_file, pidstr, strlen(pidstr), NULL);
+ if (rv == APR_SUCCESS)
+ rv = apr_file_close(pid_file);
+ if (rv == APR_SUCCESS)
+ rv = apr_file_rename(temp_fname, fname, p);
+ if (rv != APR_SUCCESS) {
+ ap_log_error(APLOG_MARK, APLOG_ERR, rv, NULL, APLOGNO(10231)
+ "%s: Failed creating pid file %s",
+ ap_server_argv0, temp_fname);
+ exit(1);
+ }
+
saved_pid = mypid;
}
--
2.25.2