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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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3
src/nxt_port.h
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@@ -26,6 +26,7 @@ struct nxt_port_handlers_s {
nxt_port_handler_t change_file;
nxt_port_handler_t new_port;
nxt_port_handler_t get_port;
nxt_port_handler_t port_ack;
nxt_port_handler_t mmap;
nxt_port_handler_t get_mmap;
@@ -84,6 +85,7 @@ typedef enum {
_NXT_PORT_MSG_CHANGE_FILE = nxt_port_handler_idx(change_file),
_NXT_PORT_MSG_NEW_PORT = nxt_port_handler_idx(new_port),
_NXT_PORT_MSG_GET_PORT = nxt_port_handler_idx(get_port),
_NXT_PORT_MSG_PORT_ACK = nxt_port_handler_idx(port_ack),
_NXT_PORT_MSG_MMAP = nxt_port_handler_idx(mmap),
_NXT_PORT_MSG_GET_MMAP = nxt_port_handler_idx(get_mmap),
@@ -120,6 +122,7 @@ typedef enum {
NXT_PORT_MSG_CHANGE_FILE = nxt_msg_last(_NXT_PORT_MSG_CHANGE_FILE),
NXT_PORT_MSG_NEW_PORT = nxt_msg_last(_NXT_PORT_MSG_NEW_PORT),
NXT_PORT_MSG_GET_PORT = nxt_msg_last(_NXT_PORT_MSG_GET_PORT),
NXT_PORT_MSG_PORT_ACK = nxt_msg_last(_NXT_PORT_MSG_PORT_ACK),
NXT_PORT_MSG_MMAP = nxt_msg_last(_NXT_PORT_MSG_MMAP)
| NXT_PORT_MSG_SYNC,
NXT_PORT_MSG_GET_MMAP = nxt_msg_last(_NXT_PORT_MSG_GET_MMAP),