allow -j (jobs) param to set zeroconf slots

If server is started in zeroconf mode, the previous behavior was that the number of jobs for any server was hardcoded to 4 * number of cpus.

This commit allows distccd to be invoked in zeroconf mode with the -j parameter to specify n_jobs, the maximum number of concurrent jobs for this server.

If no -j is specified, then this host will publish its n_jobs to be 2 * number of cores + 2.  (Note: this is the same behavior as when invoking a non-zerconf server without specifying -j.)
To maintain backward compatibily, if a distccd zeroconf server doesn't publish a value for n_jobs, then it will be assigned a default n_jobs equal to the previous behavior of 4 * number of cores.

man/distccd.1

@@ -215,6 +215,8 @@ DNS Service Discovery (DNS-SD).  This allows distcc clients on the local
 network to access this distccd server without explicitly listing its host
 name or IP address in their distcc host list: the distcc clients can
 just use "+zeroconf" in their distcc host lists.
+Can optionally use -j parameter to specify the maximum number of jobs
+that this server can process concurrently.
 .B This option is only available if distccd was compiled with
 .B Avahi support enabled.
 .TP

src/dparent.c

@@ -141,7 +141,7 @@ int dcc_standalone_server(void)
 #ifdef HAVE_AVAHI
     /* Zeroconf registration */
     if (opt_zeroconf) {
-        if (!(avahi = dcc_zeroconf_register((uint16_t) arg_port, n_cpus)))
+        if (!(avahi = dcc_zeroconf_register((uint16_t) arg_port, n_cpus, dcc_max_kids)))
             return EXIT_CONNECT_FAILED;
     }
 #endif

src/zeroconf-reg.c

@@ -52,6 +52,7 @@ struct context {
     AvahiEntryGroup *group;
     uint16_t port;
     int n_cpus;
+    int n_jobs;
 };
 
 static void publish_reply(AvahiEntryGroup *g, AvahiEntryGroupState state, void *userdata);
@@ -73,9 +74,10 @@ static void register_stuff(struct context *ctx) {
     }
 
     if (avahi_entry_group_is_empty(ctx->group)) {
-        char cpus[32], machine[64] = "cc_machine=", version[64] = "cc_version=", *m, *v;
+        char cpus[32], jobs[32], machine[64] = "cc_machine=", version[64] = "cc_version=", *m, *v;
 
         snprintf(cpus, sizeof(cpus), "cpus=%i", ctx->n_cpus);
+        snprintf(jobs, sizeof(jobs), "jobs=%i", ctx->n_jobs);
         v = dcc_get_gcc_version(version+11, sizeof(version)-11);
         m = dcc_get_gcc_machine(machine+11, sizeof(machine)-11);
 
@@ -93,6 +95,7 @@ static void register_stuff(struct context *ctx) {
                     ctx->port,
                     "txtvers=1",
                     cpus,
+                    jobs,
                     "distcc="PACKAGE_VERSION,
                     "gnuhost="GNU_HOST,
                     v ? version : NULL,
@@ -222,8 +225,8 @@ static void client_callback(AvahiClient *client, AvahiClientState state, void *u
     }
 }
 
-/* register a distcc service in DNS-SD/mDNS with the given port and number of CPUs */
-void* dcc_zeroconf_register(uint16_t port, int n_cpus) {
+/* register a distcc service in DNS-SD/mDNS with the given port, number of CPUs, and maximum concurrent jobs */
+void* dcc_zeroconf_register(uint16_t port, int n_cpus, int n_jobs) {
     struct context *ctx = NULL;
     char service[256] = "distcc@";
     int error;
@@ -235,6 +238,7 @@ void* dcc_zeroconf_register(uint16_t port, int n_cpus) {
     ctx->threaded_poll = NULL;
     ctx->port = port;
     ctx->n_cpus = n_cpus;
+    ctx->n_jobs = n_jobs;
 
     /* Prepare service name */
     gethostname(service+7, sizeof(service)-8);

src/zeroconf.c

@@ -77,6 +77,7 @@ struct host {
     AvahiAddress address;
     uint16_t port;
     int n_cpus;
+    int n_jobs;
 
     AvahiServiceResolver *resolver;
 };
@@ -163,9 +164,9 @@ static int write_hosts(struct daemon_data *d) {
             /* Not yet fully resolved */
             continue;
 	if (h->address.proto == AVAHI_PROTO_INET6)
-	    snprintf(t, sizeof(t), "[%s]:%u/%i\n", avahi_address_snprint(a, sizeof(a), &h->address), h->port, d->n_slots * h->n_cpus);
+	    snprintf(t, sizeof(t), "[%s]:%u/%i\n", avahi_address_snprint(a, sizeof(a), &h->address), h->port, h->n_jobs);
 	else
-	    snprintf(t, sizeof(t), "%s:%u/%i\n", avahi_address_snprint(a, sizeof(a), &h->address), h->port, d->n_slots * h->n_cpus);
+	    snprintf(t, sizeof(t), "%s:%u/%i\n", avahi_address_snprint(a, sizeof(a), &h->address), h->port, h->n_jobs);
 
         if (dcc_writex(d->fd, t, strlen(t)) != 0) {
             rs_log_crit("write() failed: %s\n", strerror(errno));
@@ -276,6 +277,21 @@ static void resolve_reply(
                 avahi_free(value);
             }
 
+            /* Look for the number of jobs in TXT RRs, and if not found, then set n_jobs = 4 * n_cpus */
+            for (i = txt; i; i = i->next) {
+                char *key, *value;
+
+                if (avahi_string_list_get_pair(i, &key, &value, NULL) < 0)
+                    continue;
+
+                if (!strcmp(key, "jobs"))
+                    if ((h->n_jobs = atoi(value)) <= 0)
+                        h->n_jobs = 4 * h->n_cpus;
+
+                avahi_free(key);
+                avahi_free(value);
+            }
+
             h->address = *a;
             h->port = port;
 
@@ -350,6 +366,7 @@ static void browse_reply(
                 h->protocol = protocol;
                 h->next = d->hosts;
                 h->n_cpus = 1;
+                h->n_jobs = 4;
                 d->hosts = h;
             }
 

src/zeroconf.h

@@ -25,7 +25,7 @@
 
 int dcc_zeroconf_add_hosts(struct dcc_hostdef **re_list, int *ret_nhosts, int slots, struct dcc_hostdef **ret_prev);
 
-void *dcc_zeroconf_register(uint16_t port, int n_cpus);
+void *dcc_zeroconf_register(uint16_t port, int n_cpus, int n_jobs);
 int dcc_zeroconf_unregister(void*);
 
 char* dcc_get_gcc_version(char *s, size_t nbytes);