git/list[1] front-page[2] threads[3] people[4] search[5] about
 

[RFC PATCH v2 05/16] Add multi_ack_2 capability to fetch-pack/upload-pack

From
Shawn O. Pearce <spearce@spearce.org>
Date
Oct 13, 2009, 02:25 UTC
Message-ID
<1255400715-10508-6-git-send-email-spearce@spearce.org>
In-Reply-To
<1255400715-10508-1-git-send-email-spearce@spearce.org>

When multi_ack_2 is enabled the ACK continue messages returned by the remote upload-pack are broken out to describe the different states within the peer. This permits the client to better understand the server's in-memory state.

The fetch-pack/upload-pack protocol now looks like:
NAK
---------------------------------
  Always sent in response to "done" if there was no common base
  selected from the "have" lines (or no have lines were sent).
  * no multi_ack or multi_ack_2:
    Sent when the client has sent a pkt-line flush ("0000") and
    the server has not yet found a common base object.
  * either multi_ack or multi_ack_2:
    Always sent in response to a pkt-line flush.
ACK %s
-----------------------------------
  * no multi_ack or multi_ack_2:
    Sent in response to "have" when the object exists on the remote
    side and is therefore an object in common between the peers.
    The argument is the SHA-1 of the common object.
  * either multi_ack or multi_ack_2:
    Sent in response to "done" if there are common objects.
    The argument is the last SHA-1 determined to be common.
ACK %s continue
-----------------------------------
  * multi_ack only:
    Sent in response to "have".
    The remote side wants the client to consider this object as
    common, and immediately stop transmitting additional "have"
    lines for objects that are reachable from it.  The reason
    the client should stop is not given, but is one of the two
    cases below available under multi_ack_2.
ACK %s common
-----------------------------------
  * multi_ack_2 only:
    Sent in response to "have".  Both sides have this object.
    Like with "ACK %s continue" above the client should stop
    sending have lines reachable for objects from the argument.
ACK %s ready
-----------------------------------
  * multi_ack_2 only:
    Sent in response to "have".
    The client should stop transmitting objects which are reachable
    from the argument, and send "done" soon to get the objects.
    If the remote side has the specified object, it should
    first send an "ACK %s common" message prior to sending
    "ACK %s ready".
    Clients may still submit additional "have" lines if there are
    more side branches for the client to explore that might be added
    to the common set and reduce the number of objects to transfer.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---
 builtin-fetch-pack.c |   41 ++++++++++++++++++++++++++++++++---------
 upload-pack.c        |   31 ++++++++++++++++++-------------
 2 files changed, 50 insertions(+), 22 deletions(-)
diff --git a/builtin-fetch-pack.c b/builtin-fetch-pack.c
index 7c09d46..b68b3eb 100644
--- a/builtin-fetch-pack.c
+++ b/builtin-fetch-pack.c
@@ -157,7 +157,15 @@ static const unsigned char *get_rev(void)
 	return commit->object.sha1;
 }
 
-static int get_ack(int fd, unsigned char *result_sha1)
+enum ack_type {
+	NAK = 0,
+	ACK,
+	ACK_continue,
+	ACK_common,
+	ACK_ready
+};
+
+static enum ack_type get_ack(int fd, unsigned char *result_sha1)
 {
 	static char line[1000];
 	int len = packet_read_line(fd, line, sizeof(line));
@@ -167,12 +175,16 @@ static int get_ack(int fd, unsigned char *result_sha1)
 	if (line[len-1] == '\n')
 		line[--len] = 0;
 	if (!strcmp(line, "NAK"))
-		return 0;
+		return NAK;
 	if (!prefixcmp(line, "ACK ")) {
 		if (!get_sha1_hex(line+4, result_sha1)) {
 			if (strstr(line+45, "continue"))
-				return 2;
-			return 1;
+				return ACK_continue;
+			if (strstr(line+45, "common"))
+				return ACK_common;
+			if (strstr(line+45, "ready"))
+				return ACK_ready;
+			return ACK;
 		}
 	}
 	die("git fetch_pack: expected ACK/NAK, got '%s'", line);
@@ -218,7 +230,8 @@ static int find_common(int fd[2], unsigned char *result_sha1,
 		remote_hex = sha1_to_hex(remote);
 		if (!fetching) {
 			struct strbuf c = STRBUF_INIT;
-			if (multi_ack)          strbuf_addstr(&c, " multi_ack");
+			if (multi_ack == 2)     strbuf_addstr(&c, " multi_ack_2");
+			if (multi_ack == 1)     strbuf_addstr(&c, " multi_ack");
 			if (use_sideband == 2)  strbuf_addstr(&c, " side-band-64k");
 			if (use_sideband == 1)  strbuf_addstr(&c, " side-band");
 			if (args.use_thin_pack) strbuf_addstr(&c, " thin-pack");
@@ -298,18 +311,23 @@ static int find_common(int fd[2], unsigned char *result_sha1,
 				if (args.verbose && ack)
 					fprintf(stderr, "got ack %d %s\n", ack,
 							sha1_to_hex(result_sha1));
-				if (ack == 1) {
+				switch (ack) {
+				case ACK:
 					flushes = 0;
 					multi_ack = 0;
 					retval = 0;
 					goto done;
-				} else if (ack == 2) {
+				case ACK_common:
+				case ACK_ready:
+				case ACK_continue: {
 					struct commit *commit =
 						lookup_commit(result_sha1);
 					mark_common(commit, 0, 1);
 					retval = 0;
 					in_vain = 0;
 					got_continue = 1;
+					break;
+					}
 				}
 			} while (ack);
 			flushes--;
@@ -336,7 +354,7 @@ done:
 			if (args.verbose)
 				fprintf(stderr, "got ack (%d) %s\n", ack,
 					sha1_to_hex(result_sha1));
-			if (ack == 1)
+			if (ack == ACK)
 				return 0;
 			multi_ack = 1;
 			continue;
@@ -618,7 +636,12 @@ static struct ref *do_fetch_pack(int fd[2],
 
 	if (is_repository_shallow() && !server_supports("shallow"))
 		die("Server does not support shallow clients");
-	if (server_supports("multi_ack")) {
+	if (server_supports("multi_ack_2")) {
+		if (args.verbose)
+			fprintf(stderr, "Server supports multi_ack_2\n");
+		multi_ack = 2;
+	}
+	else if (server_supports("multi_ack")) {
 		if (args.verbose)
 			fprintf(stderr, "Server supports multi_ack\n");
 		multi_ack = 1;
diff --git a/upload-pack.c b/upload-pack.c
index 38ddac2..5024b59 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -498,7 +498,7 @@ static int get_common_commits(void)
 {
 	static char line[1000];
 	unsigned char sha1[20];
-	char hex[41], last_hex[41];
+	char last_hex[41];
 
 	save_commit_buffer = 0;
 
@@ -515,19 +515,22 @@ static int get_common_commits(void)
 		if (!prefixcmp(line, "have ")) {
 			switch (got_sha1(line+5, sha1)) {
 			case -1: /* they have what we do not */
-				if (multi_ack && ok_to_give_up())
-					packet_write(1, "ACK %s continue\n",
-						     sha1_to_hex(sha1));
+				if (multi_ack && ok_to_give_up()) {
+					const char *hex = sha1_to_hex(sha1);
+					if (multi_ack == 2)
+						packet_write(1, "ACK %s ready\n", hex);
+					else
+						packet_write(1, "ACK %s continue\n", hex);
+				}
 				break;
 			default:
-				memcpy(hex, sha1_to_hex(sha1), 41);
-				if (multi_ack) {
-					const char *msg = "ACK %s continue\n";
-					packet_write(1, msg, hex);
-					memcpy(last_hex, hex, 41);
-				}
+				memcpy(last_hex, sha1_to_hex(sha1), 41);
+				if (multi_ack == 2)
+					packet_write(1, "ACK %s common\n", last_hex);
+				else if (multi_ack)
+					packet_write(1, "ACK %s continue\n", last_hex);
 				else if (have_obj.nr == 1)
-					packet_write(1, "ACK %s\n", hex);
+					packet_write(1, "ACK %s\n", last_hex);
 				break;
 			}
 			continue;
@@ -587,7 +590,9 @@ static void receive_needs(void)
 		    get_sha1_hex(line+5, sha1_buf))
 			die("git upload-pack: protocol error, "
 			    "expected to get sha, not '%s'", line);
-		if (strstr(line+45, "multi_ack"))
+		if (strstr(line+45, "multi_ack_2"))
+			multi_ack = 2;
+		else if (strstr(line+45, "multi_ack"))
 			multi_ack = 1;
 		if (strstr(line+45, "thin-pack"))
 			use_thin_pack = 1;
@@ -681,7 +686,7 @@ static int send_ref(const char *refname, const unsigned char *sha1, int flag, vo
 {
 	static const char *capabilities = "multi_ack thin-pack side-band"
 		" side-band-64k ofs-delta shallow no-progress"
-		" include-tag";
+		" include-tag multi_ack_2";
 	struct object *o = parse_object(sha1);
 
 	if (!o)

-- 
1.6.5.52.g0ff2e
Previous: Shawn O. PearceNext: Jakub Narebski
Message 8 of 38 in “Return of smart HTTP”
  1. 00/16 Return of smart HTTPShawn O. Pearce, Oct 13, 2009
  2. 01/16 pkt-line: Add strbuf based functionsShawn O. Pearce, Oct 13, 2009
  3. Johannes SixtOct 13, 2009
  4. Shawn O. PearceOct 13, 2009
  5. 02/16 pkt-line: Make packet_read_line easier to debugShawn O. Pearce, Oct 13, 2009
  6. 03/16 fetch-pack: Use a strbuf to compose the want listShawn O. Pearce, Oct 13, 2009
  7. 04/16 Move "get_ack()" back to fetch-packShawn O. Pearce, Oct 13, 2009
  8. 05/16 Add multi_ack_2 capability to fetch-pack/upload-packShawn O. Pearce, Oct 13, 2009
  9. Jakub NarebskiOct 13, 2009
  10. Shawn O. PearceOct 13, 2009
  11. 06/16 remote-curl: Refactor walker initializationShawn O. Pearce, Oct 13, 2009
  12. 07/16 remote-helpers: Fetch more than one ref in a batchShawn O. Pearce, Oct 13, 2009
  13. Daniel BarkalowOct 13, 2009
  14. Shawn O. PearceOct 13, 2009
  15. 08/16 remote-helpers: Support custom transport optionsShawn O. Pearce, Oct 13, 2009
  16. Daniel BarkalowOct 13, 2009
  17. Shawn O. PearceOct 13, 2009
  18. Daniel BarkalowOct 13, 2009
  19. Shawn O. PearceOct 13, 2009
  20. Daniel BarkalowOct 13, 2009
  21. Shawn O. PearceOct 13, 2009
  22. 09/16 Move WebDAV HTTP push under remote-curlShawn O. Pearce, Oct 13, 2009
  23. Mike HommeyOct 13, 2009
  24. Johannes SchindelinOct 13, 2009
  25. 10/16 Git-aware CGI to provide dumb HTTP transportShawn O. Pearce, Oct 13, 2009
  26. Johannes SixtOct 13, 2009
  27. 11/16 Add one shot RPC options to upload-pack, receive-packShawn O. Pearce, Oct 13, 2009
  28. 12/16 Smart fetch and push over HTTP: server sideShawn O. Pearce, Oct 13, 2009
  29. Johannes SixtOct 13, 2009
  30. Shawn O. PearceOct 13, 2009
  31. 13/16 Discover refs via smart HTTP server when availableShawn O. Pearce, Oct 13, 2009
  32. 14/16 Smart push over HTTP: client sideShawn O. Pearce, Oct 13, 2009
  33. Felipe ContrerasOct 13, 2009
  34. 15/16 Smart fetch over HTTP: client sideShawn O. Pearce, Oct 13, 2009
  35. 16/16 Smart HTTP fetch: gzip requestsShawn O. Pearce, Oct 13, 2009
  36. Junio C HamanoOct 13, 2009
  37. eduard stefanOct 13, 2009
  38. Junio C HamanoOct 13, 2009

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.