Smart HTTP fetch: gzip requests

The upload-pack requests are mostly plain text and they compress
rather well.  Deflating them with Content-Encoding: gzip can easily
drop the size of the request by 50%, reducing the amount of data
to transfer as we negotiate the common commits.

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

diff --git a/remote-curl.c b/remote-curl.c
index 0eb6fc48fbb8f9c599386381539bd2fa4d23e40e..0d7cf16e9c06d556cad8d92b6598a8da079426a4 100644 (file)
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -289,6 +289,7 @@ struct rpc_state {
        int in;
        int out;
        struct strbuf result;
+       unsigned gzip_request : 1;
 };
 
 static size_t rpc_out(void *ptr, size_t eltsize,
@@ -327,6 +328,8 @@ static int post_rpc(struct rpc_state *rpc)
        struct active_request_slot *slot;
        struct slot_results results;
        struct curl_slist *headers = NULL;
+       int use_gzip = rpc->gzip_request;
+       char *gzip_body = NULL;
        int err = 0, large_request = 0;
 
        /* Try to load the entire request, if we can fit it into the
@@ -340,6 +343,7 @@ static int post_rpc(struct rpc_state *rpc)
 
                if (left < LARGE_PACKET_MAX) {
                        large_request = 1;
+                       use_gzip = 0;
                        break;
                }
 
@@ -355,6 +359,7 @@ static int post_rpc(struct rpc_state *rpc)
        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);
+       curl_easy_setopt(slot->curl, CURLOPT_ENCODING, "");
 
        headers = curl_slist_append(headers, rpc->hdr_content_type);
        headers = curl_slist_append(headers, rpc->hdr_accept);
@@ -372,6 +377,49 @@ static int post_rpc(struct rpc_state *rpc)
                        fflush(stderr);
                }
 
+       } else if (use_gzip && 1024 < rpc->len) {
+               /* The client backend isn't giving us compressed data so
+                * we can try to deflate it ourselves, this may save on.
+                * the transfer time.
+                */
+               size_t size;
+               z_stream stream;
+               int ret;
+
+               memset(&stream, 0, sizeof(stream));
+               ret = deflateInit2(&stream, Z_BEST_COMPRESSION,
+                               Z_DEFLATED, (15 + 16),
+                               8, Z_DEFAULT_STRATEGY);
+               if (ret != Z_OK)
+                       die("cannot deflate request; zlib init error %d", ret);
+               size = deflateBound(&stream, rpc->len);
+               gzip_body = xmalloc(size);
+
+               stream.next_in = (unsigned char *)rpc->buf;
+               stream.avail_in = rpc->len;
+               stream.next_out = (unsigned char *)gzip_body;
+               stream.avail_out = size;
+
+               ret = deflate(&stream, Z_FINISH);
+               if (ret != Z_STREAM_END)
+                       die("cannot deflate request; zlib deflate error %d", ret);
+
+               ret = deflateEnd(&stream);
+               if (ret != Z_OK)
+                       die("cannot deflate request; zlib end error %d", ret);
+
+               size = stream.total_out;
+
+               headers = curl_slist_append(headers, "Content-Encoding: gzip");
+               curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDS, gzip_body);
+               curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDSIZE, size);
+
+               if (options.verbosity > 1) {
+                       fprintf(stderr, "POST %s (gzip %lu to %lu bytes)\n",
+                               rpc->service_name,
+                               (unsigned long)rpc->len, (unsigned long)size);
+                       fflush(stderr);
+               }
        } else {
                /* We know the complete request size in advance, use the
                 * more normal Content-Length approach.
@@ -398,6 +446,7 @@ static int post_rpc(struct rpc_state *rpc)
        }
 
        curl_slist_free_all(headers);
+       free(gzip_body);
        return err;
 }
 
@@ -523,6 +572,7 @@ static int fetch_git(struct discovery *heads,
        memset(&rpc, 0, sizeof(rpc));
        rpc.service_name = "git-upload-pack",
        rpc.argv = argv;
+       rpc.gzip_request = 1;
 
        err = rpc_service(&rpc, heads);
        if (rpc.result.len)