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authorCory Fields <cory-nospam-@coryfields.com>2017-11-01 12:02:57 -0400
committerCory Fields <cory-nospam-@coryfields.com>2017-11-01 17:49:07 -0400
commit6b58360f9b64eb0b680a662fdfd590e47f115f44 (patch)
tree2e80850dcc9c56af25f4771648b67179994dee35 /src/httpserver.cpp
parentcffa5ee132f3ef6a8d138eb98d15da2b61999ca4 (diff)
rpc: work-around an upstream libevent bug
A rare race condition may trigger while awaiting the body of a message, see upsteam commit 5ff8eb26371c4dc56f384b2de35bea2d87814779 for details. This may fix some reported rpc hangs/crashes.
Diffstat (limited to 'src/httpserver.cpp')
-rw-r--r--src/httpserver.cpp28
1 files changed, 26 insertions, 2 deletions
diff --git a/src/httpserver.cpp b/src/httpserver.cpp
index 31b6a3705b..63a634b244 100644
--- a/src/httpserver.cpp
+++ b/src/httpserver.cpp
@@ -24,6 +24,7 @@
#include <event2/thread.h>
#include <event2/buffer.h>
+#include <event2/bufferevent.h>
#include <event2/util.h>
#include <event2/keyvalq_struct.h>
@@ -239,6 +240,16 @@ static std::string RequestMethodString(HTTPRequest::RequestMethod m)
/** HTTP request callback */
static void http_request_cb(struct evhttp_request* req, void* arg)
{
+ // Disable reading to work around a libevent bug, fixed in 2.2.0.
+ if (event_get_version_number() < 0x02020001) {
+ evhttp_connection* conn = evhttp_request_get_connection(req);
+ if (conn) {
+ bufferevent* bev = evhttp_connection_get_bufferevent(conn);
+ if (bev) {
+ bufferevent_disable(bev, EV_READ);
+ }
+ }
+ }
std::unique_ptr<HTTPRequest> hreq(new HTTPRequest(req));
LogPrint(BCLog::HTTP, "Received a %s request for %s from %s\n",
@@ -601,8 +612,21 @@ void HTTPRequest::WriteReply(int nStatus, const std::string& strReply)
struct evbuffer* evb = evhttp_request_get_output_buffer(req);
assert(evb);
evbuffer_add(evb, strReply.data(), strReply.size());
- HTTPEvent* ev = new HTTPEvent(eventBase, true,
- std::bind(evhttp_send_reply, req, nStatus, (const char*)nullptr, (struct evbuffer *)nullptr));
+ auto req_copy = req;
+ HTTPEvent* ev = new HTTPEvent(eventBase, true, [req_copy, nStatus]{
+ evhttp_send_reply(req_copy, nStatus, nullptr, nullptr);
+ // Re-enable reading from the socket. This is the second part of the libevent
+ // workaround above.
+ if (event_get_version_number() < 0x02020001) {
+ evhttp_connection* conn = evhttp_request_get_connection(req_copy);
+ if (conn) {
+ bufferevent* bev = evhttp_connection_get_bufferevent(conn);
+ if (bev) {
+ bufferevent_enable(bev, EV_READ | EV_WRITE);
+ }
+ }
+ }
+ });
ev->trigger(nullptr);
replySent = true;
req = nullptr; // transferred back to main thread