Smart push over HTTP: client side

The git-remote-curl backend detects if the remote server supports
the git-receive-pack service, and if so, runs git-send-pack in a
pipe to dump the command and pack data as a single POST request.

The advertisements from the server that were obtained during the
discovery are passed into git-send-pack before the POST request
starts.  This permits git-send-pack to operate largely unmodified.

For smaller packs (those under 1 MiB) a HTTP/1.0 POST with a
Content-Length is used, permitting interaction with any server.
The 1 MiB limit is arbitrary, but is sufficent to fit most deltas
created by human authors against text sources with the occasional
small binary file (e.g. few KiB icon image).  The configuration
option http.postBuffer can be used to increase (or shink) this
buffer if the default is not sufficient.

For larger packs which cannot be spooled entirely into the helper's
memory space (due to http.postBuffer being too small), the POST
request requires HTTP/1.1 and sets "Transfer-Encoding: chunked".
This permits the client to upload an unknown amount of data in one
HTTP transaction without needing to pregenerate the entire pack
file locally.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
CC: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 233 insertions, 2 deletions

diff --git a/remote-curl.c b/remote-curl.c
index 3917d45de..f1206cb57 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -6,6 +6,7 @@
 #include "exec_cmd.h"
 #include "run-command.h"
 #include "pkt-line.h"
+#include "sideband.h"
 
 static struct remote *remote;
 static const char *url;
@@ -16,7 +17,8 @@ struct options {
 	unsigned long depth;
 	unsigned progress : 1,
 		followtags : 1,
-		dry_run : 1;
+		dry_run : 1,
+		thin : 1;
 };
 static struct options options;
 
@@ -274,6 +276,188 @@ static void output_refs(struct ref *refs)
 	free_refs(refs);
 }
 
+struct rpc_state {
+	const char *service_name;
+	const char **argv;
+	char *service_url;
+	char *hdr_content_type;
+	char *hdr_accept;
+	char *buf;
+	size_t alloc;
+	size_t len;
+	size_t pos;
+	int in;
+	int out;
+	struct strbuf result;
+};
+
+static size_t rpc_out(void *ptr, size_t eltsize,
+		size_t nmemb, void *buffer_)
+{
+	size_t max = eltsize * nmemb;
+	struct rpc_state *rpc = buffer_;
+	size_t avail = rpc->len - rpc->pos;
+
+	if (!avail) {
+		avail = packet_read_line(rpc->out, rpc->buf, rpc->alloc);
+		if (!avail)
+			return 0;
+		rpc->pos = 0;
+		rpc->len = avail;
+	}
+
+	if (max < avail);
+		avail = max;
+	memcpy(ptr, rpc->buf + rpc->pos, avail);
+	rpc->pos += avail;
+	return avail;
+}
+
+static size_t rpc_in(const void *ptr, size_t eltsize,
+		size_t nmemb, void *buffer_)
+{
+	size_t size = eltsize * nmemb;
+	struct rpc_state *rpc = buffer_;
+	write_or_die(rpc->in, ptr, size);
+	return size;
+}
+
+static int post_rpc(struct rpc_state *rpc)
+{
+	struct active_request_slot *slot;
+	struct slot_results results;
+	struct curl_slist *headers = NULL;
+	int err = 0, large_request = 0;
+
+	/* Try to load the entire request, if we can fit it into the
+	 * allocated buffer space we can use HTTP/1.0 and avoid the
+	 * chunked encoding mess.
+	 */
+	while (1) {
+		size_t left = rpc->alloc - rpc->len;
+		char *buf = rpc->buf + rpc->len;
+		int n;
+
+		if (left < LARGE_PACKET_MAX) {
+			large_request = 1;
+			break;
+		}
+
+		n = packet_read_line(rpc->out, buf, left);
+		if (!n)
+			break;
+		rpc->len += n;
+	}
+
+	slot = get_active_slot();
+	slot->results = &results;
+
+	curl_easy_setopt(slot->curl, CURLOPT_POST, 1);
+	curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 0);
+	curl_easy_setopt(slot->curl, CURLOPT_URL, rpc->service_url);
+
+	headers = curl_slist_append(headers, rpc->hdr_content_type);
+	headers = curl_slist_append(headers, rpc->hdr_accept);
+
+	if (large_request) {
+		/* The request body is large and the size cannot be predicted.
+		 * We must use chunked encoding to send it.
+		 */
+		headers = curl_slist_append(headers, "Expect: 100-continue");
+		headers = curl_slist_append(headers, "Transfer-Encoding: chunked");
+		curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, rpc_out);
+		curl_easy_setopt(slot->curl, CURLOPT_INFILE, rpc);
+		if (options.verbosity > 1) {
+			fprintf(stderr, "POST %s (chunked)\n", rpc->service_name);
+			fflush(stderr);
+		}
+
+	} else {
+		/* We know the complete request size in advance, use the
+		 * more normal Content-Length approach.
+		 */
+		curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDS, rpc->buf);
+		curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDSIZE, rpc->len);
+		if (options.verbosity > 1) {
+			fprintf(stderr, "POST %s (%lu bytes)\n",
+				rpc->service_name, (unsigned long)rpc->len);
+			fflush(stderr);
+		}
+	}
+
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, headers);
+	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, rpc_in);
+	curl_easy_setopt(slot->curl, CURLOPT_FILE, rpc);
+
+	slot->curl_result = curl_easy_perform(slot->curl);
+	finish_active_slot(slot);
+
+	if (results.curl_result != CURLE_OK) {
+		err |= error("RPC failed; result=%d, HTTP code = %ld",
+			results.curl_result, results.http_code);
+	}
+
+	curl_slist_free_all(headers);
+	return err;
+}
+
+static int rpc_service(struct rpc_state *rpc, struct discovery *heads)
+{
+	const char *svc = rpc->service_name;
+	struct strbuf buf = STRBUF_INIT;
+	struct child_process client;
+	int err = 0;
+
+	init_walker();
+	memset(&client, 0, sizeof(client));
+	client.in = -1;
+	client.out = -1;
+	client.git_cmd = 1;
+	client.argv = rpc->argv;
+	if (start_command(&client))
+		exit(1);
+	if (heads)
+		write_or_die(client.in, heads->buf, heads->len);
+
+	rpc->alloc = http_post_buffer;
+	rpc->buf = xmalloc(rpc->alloc);
+	rpc->in = client.in;
+	rpc->out = client.out;
+	strbuf_init(&rpc->result, 0);
+
+	strbuf_addf(&buf, "%s/%s", url, svc);
+	rpc->service_url = strbuf_detach(&buf, NULL);
+
+	strbuf_addf(&buf, "Content-Type: application/x-%s-request", svc);
+	rpc->hdr_content_type = strbuf_detach(&buf, NULL);
+
+	strbuf_addf(&buf, "Accept: application/x-%s-response", svc);
+	rpc->hdr_accept = strbuf_detach(&buf, NULL);
+
+	while (!err) {
+		int n = packet_read_line(rpc->out, rpc->buf, rpc->alloc);
+		if (!n)
+			break;
+		rpc->pos = 0;
+		rpc->len = n;
+		err |= post_rpc(rpc);
+	}
+	strbuf_read(&rpc->result, client.out, 0);
+
+	close(client.in);
+	close(client.out);
+	client.in = -1;
+	client.out = -1;
+
+	err |= finish_command(&client);
+	free(rpc->service_url);
+	free(rpc->hdr_content_type);
+	free(rpc->hdr_accept);
+	free(rpc->buf);
+	strbuf_release(&buf);
+	return err;
+}
+
 static int fetch_dumb(int nr_heads, struct ref **to_fetch)
 {
 	char **targets = xmalloc(nr_heads * sizeof(char*));
@@ -371,6 +555,52 @@ static int push_dav(int nr_spec, char **specs)
 	return 0;
 }
 
+static int push_git(struct discovery *heads, int nr_spec, char **specs)
+{
+	struct rpc_state rpc;
+	const char **argv;
+	int argc = 0, i, err;
+
+	argv = xmalloc((10 + nr_spec) * sizeof(char*));
+	argv[argc++] = "send-pack";
+	argv[argc++] = "--stateless-rpc";
+	argv[argc++] = "--helper-status";
+	if (options.thin)
+		argv[argc++] = "--thin";
+	if (options.dry_run)
+		argv[argc++] = "--dry-run";
+	if (options.verbosity > 1)
+		argv[argc++] = "--verbose";
+	argv[argc++] = url;
+	for (i = 0; i < nr_spec; i++)
+		argv[argc++] = specs[i];
+	argv[argc++] = NULL;
+
+	memset(&rpc, 0, sizeof(rpc));
+	rpc.service_name = "git-receive-pack",
+	rpc.argv = argv;
+
+	err = rpc_service(&rpc, heads);
+	if (rpc.result.len)
+		safe_write(1, rpc.result.buf, rpc.result.len);
+	strbuf_release(&rpc.result);
+	free(argv);
+	return err;
+}
+
+static int push(int nr_spec, char **specs)
+{
+	struct discovery *heads = discover_refs("git-receive-pack");
+	int ret;
+
+	if (heads->proto_git)
+		ret = push_git(heads, nr_spec, specs);
+	else
+		ret = push_dav(nr_spec, specs);
+	free_discovery(heads);
+	return ret;
+}
+
 static void parse_push(struct strbuf *buf)
 {
 	char **specs = NULL;
@@ -391,7 +621,7 @@ static void parse_push(struct strbuf *buf)
 			break;
 	} while (1);
 
-	if (push_dav(nr_spec, specs))
+	if (push(nr_spec, specs))
 		exit(128); /* error already reported */
 	for (i = 0; i < nr_spec; i++)
 		free(specs[i]);
@@ -414,6 +644,7 @@ int main(int argc, const char **argv)
 
 	options.verbosity = 1;
 	options.progress = !!isatty(2);
+	options.thin = 1;
 
 	remote = remote_get(argv[1]);