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authorJeff King <peff@peff.net>2014-02-18 05:34:20 -0500
committerJunio C Hamano <gitster@pobox.com>2014-02-18 15:50:57 -0800
commitbeed336c3e35acfd7aad9033eb9294e42b9530af (patch)
tree3837ffddfd800be487ea85cc2a0909b110fd0b0b
parent5f95c9f850b19b368c43ae399cc831b17a26a5ac (diff)
downloadgit-beed336c3e35acfd7aad9033eb9294e42b9530af.tar.gz
git-beed336c3e35acfd7aad9033eb9294e42b9530af.tar.xz
http: never use curl_easy_perform
We currently don't reuse http connections when fetching via the smart-http protocol. This is bad because the TCP handshake introduces latency, and especially because SSL connection setup may be non-trivial. We can fix it by consistently using curl's "multi" interface. The reason is rather complicated: Our http code has two ways of being used: queuing many "slots" to be fetched in parallel, or fetching a single request in a blocking manner. The parallel code is built on curl's "multi" interface. Most of the single-request code uses http_request, which is built on top of the parallel code (we just feed it one slot, and wait until it finishes). However, one could also accomplish the single-request scheme by avoiding curl's multi interface entirely and just using curl_easy_perform. This is simpler, and is used by post_rpc in the smart-http protocol. It does work to use the same curl handle in both contexts, as long as it is not at the same time. However, internally curl may not share all of the cached resources between both contexts. In particular, a connection formed using the "multi" code will go into a reuse pool connected to the "multi" object. Further requests using the "easy" interface will not be able to reuse that connection. The smart http protocol does ref discovery via http_request, which uses the "multi" interface, and then follows up with the "easy" interface for its rpc calls. As a result, we make two HTTP connections rather than reusing a single one. We could teach the ref discovery to use the "easy" interface. But it is only once we have done this discovery that we know whether the protocol will be smart or dumb. If it is dumb, then our further requests, which want to fetch objects in parallel, will not be able to reuse the same connection. Instead, this patch switches post_rpc to build on the parallel interface, which means that we use it consistently everywhere. It's a little more complicated to use, but since we have the infrastructure already, it doesn't add any code; we can just factor out the relevant bits from http_request. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--http.c24
-rw-r--r--http.h9
-rw-r--r--remote-curl.c5
3 files changed, 25 insertions, 13 deletions
diff --git a/http.c b/http.c
index 70eaa26e8..1212c587a 100644
--- a/http.c
+++ b/http.c
@@ -880,6 +880,20 @@ int handle_curl_result(struct slot_results *results)
}
}
+int run_one_slot(struct active_request_slot *slot,
+ struct slot_results *results)
+{
+ slot->results = results;
+ if (!start_active_slot(slot)) {
+ snprintf(curl_errorstr, sizeof(curl_errorstr),
+ "failed to start HTTP request");
+ return HTTP_START_FAILED;
+ }
+
+ run_active_slot(slot);
+ return handle_curl_result(results);
+}
+
static CURLcode curlinfo_strbuf(CURL *curl, CURLINFO info, struct strbuf *buf)
{
char *ptr;
@@ -907,7 +921,6 @@ static int http_request(const char *url,
int ret;
slot = get_active_slot();
- slot->results = &results;
curl_easy_setopt(slot->curl, CURLOPT_HTTPGET, 1);
if (result == NULL) {
@@ -942,14 +955,7 @@ static int http_request(const char *url,
curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, headers);
curl_easy_setopt(slot->curl, CURLOPT_ENCODING, "gzip");
- if (start_active_slot(slot)) {
- run_active_slot(slot);
- ret = handle_curl_result(&results);
- } else {
- snprintf(curl_errorstr, sizeof(curl_errorstr),
- "failed to start HTTP request");
- ret = HTTP_START_FAILED;
- }
+ ret = run_one_slot(slot, &results);
if (options && options->content_type)
curlinfo_strbuf(slot->curl, CURLINFO_CONTENT_TYPE,
diff --git a/http.h b/http.h
index cd37d5881..a82888445 100644
--- a/http.h
+++ b/http.h
@@ -90,6 +90,15 @@ extern void finish_active_slot(struct active_request_slot *slot);
extern void finish_all_active_slots(void);
extern int handle_curl_result(struct slot_results *results);
+/*
+ * This will run one slot to completion in a blocking manner, similar to how
+ * curl_easy_perform would work (but we don't want to use that, because
+ * we do not want to intermingle calls to curl_multi and curl_easy).
+ *
+ */
+int run_one_slot(struct active_request_slot *slot,
+ struct slot_results *results);
+
#ifdef USE_CURL_MULTI
extern void fill_active_slots(void);
extern void add_fill_function(void *data, int (*fill)(void *));
diff --git a/remote-curl.c b/remote-curl.c
index 10cb0114e..52c2d96ce 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -423,11 +423,8 @@ static int run_slot(struct active_request_slot *slot,
if (!results)
results = &results_buf;
- slot->results = results;
- slot->curl_result = curl_easy_perform(slot->curl);
- finish_active_slot(slot);
+ err = run_one_slot(slot, results);
- err = handle_curl_result(results);
if (err != HTTP_OK && err != HTTP_REAUTH) {
error("RPC failed; result=%d, HTTP code = %ld",
results->curl_result, results->http_code);