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Router: introducing the PORT_ACK message.

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The PORT_ACK message is the router's response to the application's NEW_PORT
message.  After receiving PORT_ACK, the application is safe to process requests
using this port.

This message avoids a racing condition when the application starts processing a
request from the shared queue and sends REQ_HEADERS_ACK.  The REQ_HEADERS_ACK
message contains the application port ID as reply_port, which the router uses
to send request data.  When the application creates a new port, it
immediately sends it to the main router thread.  Because the request is
processed outside the main thread, a racing condition can occur between the
receipt of the new port in the main thread and the receipt of REQ_HEADERS_ACK
in the worker router thread where the same port is specified as reply_port.
This commit is contained in:
Max Romanov
2020-10-28 00:01:46 +03:00
parent 131b6a7ffa
commit 4cb8aeb31a
4 changed files with 39 additions and 5 deletions
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37
src/nxt_unit.c
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@@ -57,6 +57,7 @@ static int nxt_unit_ready(nxt_unit_ctx_t *ctx, int ready_fd, uint32_t stream,
static int nxt_unit_process_msg(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf);
static int nxt_unit_process_new_port(nxt_unit_ctx_t *ctx,
nxt_unit_recv_msg_t *recv_msg);
static int nxt_unit_ctx_ready(nxt_unit_ctx_t *ctx);
static int nxt_unit_process_req_headers(nxt_unit_ctx_t *ctx,
nxt_unit_recv_msg_t *recv_msg);
static int nxt_unit_process_req_body(nxt_unit_ctx_t *ctx,
@@ -306,6 +307,7 @@ struct nxt_unit_ctx_impl_s {
nxt_queue_t free_rbuf;
int online;
int ready;
nxt_unit_mmap_buf_t ctx_buf[2];
nxt_unit_read_buf_t ctx_read_buf;
@@ -624,6 +626,7 @@ nxt_unit_ctx_init(nxt_unit_impl_t *lib, nxt_unit_ctx_impl_t *ctx_impl,
ctx_impl->use_count = 1;
ctx_impl->wait_items = 0;
ctx_impl->online = 1;
ctx_impl->ready = 0;
nxt_queue_init(&ctx_impl->free_req);
nxt_queue_init(&ctx_impl->free_ws);
@@ -996,6 +999,10 @@ nxt_unit_process_msg(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf)
rc = nxt_unit_process_new_port(ctx, &recv_msg);
break;
case _NXT_PORT_MSG_PORT_ACK:
rc = nxt_unit_ctx_ready(ctx);
break;
case _NXT_PORT_MSG_CHANGE_FILE:
nxt_unit_debug(ctx, "#%"PRIu32": change_file: fd %d",
port_msg->stream, recv_msg.fd[0]);
@@ -1169,8 +1176,28 @@ nxt_unit_process_new_port(nxt_unit_ctx_t *ctx, nxt_unit_recv_msg_t *recv_msg)
if (new_port_msg->id == NXT_UNIT_SHARED_PORT_ID) {
lib->shared_port = port;
} else {
nxt_unit_port_release(port);
return nxt_unit_ctx_ready(ctx);
}
nxt_unit_port_release(port);
return NXT_UNIT_OK;
}
static int
nxt_unit_ctx_ready(nxt_unit_ctx_t *ctx)
{
nxt_unit_impl_t *lib;
nxt_unit_ctx_impl_t *ctx_impl;
lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
ctx_impl->ready = 1;
if (lib->callbacks.ready_handler) {
return lib->callbacks.ready_handler(ctx);
}
return NXT_UNIT_OK;
@@ -4495,17 +4522,17 @@ nxt_unit_read_buf(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf)
nxt_unit_port_impl_t *port_impl;
struct pollfd fds[2];
lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
if (ctx_impl->wait_items > 0 || lib->shared_port == NULL) {
if (ctx_impl->wait_items > 0 || ctx_impl->ready == 0) {
return nxt_unit_ctx_port_recv(ctx, ctx_impl->read_port, rbuf);
}
port_impl = nxt_container_of(ctx_impl->read_port, nxt_unit_port_impl_t,
port);
lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
retry:
if (port_impl->from_socket == 0) {