zeromq dumpstat implementation

This tries to do as little as possible on top of zeromq,
which might not work. It sends an "id" field with each
message to keep some state. Probably this should be
inherited through the environment.

Signed-off-by: Jeff King <[email protected]>

Makefile

@@ -1014,6 +1014,7 @@ LIB_OBJS += dumpstat/dumpstat.o
 LIB_OBJS += dumpstat/fd.o
 LIB_OBJS += dumpstat/file.o
 LIB_OBJS += dumpstat/json.o
+LIB_OBJS += dumpstat/zeromq.o
 LIB_OBJS += editor.o
 LIB_OBJS += entry.o
 LIB_OBJS += environment.o
@@ -2164,6 +2165,11 @@ ifdef HAVE_BSD_KERN_PROC_SYSCTL
 	BASIC_CFLAGS += -DHAVE_BSD_KERN_PROC_SYSCTL
 endif
 
+ifdef USE_DUMPSTAT_ZEROMQ
+	EXTLIBS += -lzmq
+	COMPAT_CFLAGS += -DDUMPSTAT_ZEROMQ
+endif
+
 ifdef HAVE_GETDELIM
 	BASIC_CFLAGS += -DHAVE_GETDELIM
 endif

dumpstat/dumpstat.c

@@ -38,6 +38,8 @@ static struct dumpstat_writer *parse_writer(const char *s)
 		return dumpstat_to_fd(s + 3);
 	else if (isdigit(s[0]))
 		return dumpstat_to_fd(s);
+	else if (starts_with(s, "zeromq:"))
+		return dumpstat_to_zeromq(s + 7);
 
 	warning("unknown dumpstat type: %s", s);
 	return NULL;

dumpstat/dumpstat.h

@@ -40,6 +40,7 @@ struct dumpstat_writer {
 };
 struct dumpstat_writer *dumpstat_to_file(const char *path);
 struct dumpstat_writer *dumpstat_to_fd(const char *desc);
+struct dumpstat_writer *dumpstat_to_zeromq(const char *endpoint);
 
 struct dumpstat_formatter {
 	void (*start)(void);

dumpstat/zeromq.c

@@ -0,0 +1,55 @@
+#include "cache.h"
+#include "dumpstat/dumpstat.h"
+
+#ifndef DUMPSTAT_ZEROMQ
+struct dumpstat_writer *dumpstat_to_zeromq(const char *endpoint)
+{
+	warning("zeromq dumpstat support not built");
+	return NULL;
+}
+
+#else
+
+#include <zmq.h>
+
+static char id[256];
+static void *context;
+static void *mq;
+
+static int dumpstat_zeromq_write(const char *buf, size_t len)
+{
+	zmq_msg_t msg;
+
+	zmq_msg_init_size(&msg, len);
+	memcpy(zmq_msg_data(&msg), buf, len);
+	if (zmq_send(mq, &msg, 0) < 0) {
+		warning("unable to write to zeromq: %s", strerror(errno));
+		return -1;
+	}
+	return 0;
+}
+
+struct dumpstat_writer *dumpstat_to_zeromq(const char *endpoint)
+{
+	static struct dumpstat_writer writer = {
+		dumpstat_zeromq_write
+	};
+	int len;
+
+	len = snprintf(id, sizeof(id), "%d@", (int)getpid());
+	if (gethostname(id + len, sizeof(id) - len) < 0) {
+		warning("unable to gethostname: %s", strerror(errno));
+		return NULL;
+	}
+
+	context = zmq_init(1);
+	mq = zmq_socket(context, ZMQ_PUB);
+	if (!mq || zmq_connect(mq, endpoint) < 0) {
+		warning("unable to open zeromq socket: %s", strerror(errno));
+		return NULL;
+	}
+
+	return &writer;
+}
+
+#endif /* DUMPSTAT_ZEROMQ */