[PATCH 2 of 3 V2] chg: start server at a unique address

[Jun Wu]

# HG changeset patch
# User Jun Wu <qu...@fb.com>
# Date 1482185389 0
#      Mon Dec 19 22:09:49 2016 +0000
# Node ID 24534dee38fe515f2c406e18153f623a074148b3
# Parent  c543f9fd1a5b7657d4114e61e87a8d9bc32f7617
# Available At https://bitbucket.org/quark-zju/hg-draft
#              hg pull https://bitbucket.org/quark-zju/hg-draft -r 24534dee38fe
chg: start server at a unique address

See the previous patch for motivation. Previously, the server is started at
a globally shared address. This patch appends pid to the address so it
becomes unique.

Note: with Linux pid namespace, the address may be non-unique, but it does
not affect correctness of chg - chg client will receive an redirection and
that's it.

diff --git a/contrib/chg/chg.c b/contrib/chg/chg.c
--- a/contrib/chg/chg.c
+++ b/contrib/chg/chg.c
@@ -32,4 +32,5 @@
 struct cmdserveropts {
        char sockname[UNIX_PATH_MAX];
+       char initsockname[UNIX_PATH_MAX];
        char redirectsockname[UNIX_PATH_MAX];
        char lockfile[UNIX_PATH_MAX];
@@ -164,4 +165,8 @@ static void setcmdserveropts(struct cmds
        if (r < 0 || (size_t)r >= sizeof(opts->lockfile))
                abortmsg("too long TMPDIR or CHGSOCKNAME (r = %d)", r);
+       r = snprintf(opts->initsockname, sizeof(opts->initsockname),
+                       "%s.%u", opts->sockname, (unsigned)getpid());
+       if (r < 0 || (size_t)r >= sizeof(opts->initsockname))
+               abortmsg("too long TMPDIR or CHGSOCKNAME (r = %d)", r);
 }
 
@@ -224,5 +229,5 @@ static void execcmdserver(const struct c
                "serve",
                "--cmdserver", "chgunix",
-               "--address", opts->sockname,
+               "--address", opts->initsockname,
                "--daemon-postexec", "chdir:/",
        };
@@ -248,5 +253,5 @@ static hgclient_t *retryconnectcmdserver
        int pst = 0;
 
-       debugmsg("try connect to %s repeatedly", opts->sockname);
+       debugmsg("try connect to %s repeatedly", opts->initsockname);
 
        unsigned int timeoutsec = 60;  /* default: 60 seconds */
@@ -256,7 +261,13 @@ static hgclient_t *retryconnectcmdserver
 
        for (unsigned int i = 0; !timeoutsec || i < timeoutsec * 100; i++) {
-               hgclient_t *hgc = hgc_open(opts->sockname);
-               if (hgc)
+               hgclient_t *hgc = hgc_open(opts->initsockname);
+               if (hgc) {
+                       debugmsg("rename %s to %s", opts->initsockname,
+                                       opts->sockname);
+                       int r = rename(opts->initsockname, opts->sockname);
+                       if (r != 0)
+                               abortmsgerrno("cannot rename");
                        return hgc;
+               }
 
                if (pid > 0) {
@@ -270,5 +281,5 @@ static hgclient_t *retryconnectcmdserver
        }
 
-       abortmsg("timed out waiting for cmdserver %s", opts->sockname);
+       abortmsg("timed out waiting for cmdserver %s", opts->initsockname);
        return NULL;
 
@@ -313,5 +324,5 @@ static hgclient_t *connectcmdserver(stru
                unlink(opts->sockname);
 
-       debugmsg("start cmdserver at %s", opts->sockname);
+       debugmsg("start cmdserver at %s", opts->initsockname);
 
        pid_t pid = fork();
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