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gossip: Switch gossip_store to use a single fd

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As proposed by @rustyrussell this makes it a bit easier to truncate and sync on
read errors.

Signed-off-by: Christian Decker <decker.christian@gmail.com>
This commit is contained in:
Christian Decker
2018-03-20 16:18:18 +01:00
committed by Rusty Russell
parent 5944524d01
commit 2879d78f22
1 changed files with 25 additions and 24 deletions
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49
gossipd/gossip_store.c
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@@ -9,7 +9,8 @@
#define GOSSIP_STORE_FILENAME "gossip_store"
struct gossip_store {
int read_fd, write_fd;
int fd;
off_t read_pos, write_pos;
/* What was the size of the gossip_store when we started replaying
* it? */
@@ -18,17 +19,16 @@ struct gossip_store {
static void gossip_store_destroy(struct gossip_store *gs)
{
if (gs->read_fd != -1)
close(gs->read_fd);
close(gs->write_fd);
close(gs->fd);
}
struct gossip_store *gossip_store_new(const tal_t *ctx)
{
struct gossip_store *gs = tal(ctx, struct gossip_store);
gs->write_fd = open(GOSSIP_STORE_FILENAME, O_RDWR|O_APPEND|O_CREAT, 0600);
gs->read_fd = open(GOSSIP_STORE_FILENAME, O_RDONLY);
gs->replaysize = lseek(gs->write_fd, 0, SEEK_END);
gs->fd = open(GOSSIP_STORE_FILENAME, O_RDWR|O_APPEND|O_CREAT, 0600);
gs->read_pos = 0;
gs->write_pos = lseek(gs->fd, 0, SEEK_END);
gs->replaysize = gs->write_pos;
tal_add_destructor(gs, gossip_store_destroy);
@@ -40,17 +40,11 @@ void gossip_store_append(struct gossip_store *gs, const u8 *msg)
u16 msglen = tal_len(msg);
beint16_t belen = cpu_to_be16(msglen);
/* FIXME: this method of detecting replayed messages is best effort
* only. It should avoid doubling the store file size on every start,
* but it'll allow the last few messages to be duplicated since replay
* and write are async, and we'll think we are done replaying a bit too
* early. */
/* Check if we are replaying the store */
if (lseek(gs->read_fd, 0, SEEK_CUR) < gs->replaysize)
if (pwrite(gs->fd, &belen, sizeof(belen), gs->write_pos) != 2 ||
pwrite(gs->fd, msg, msglen, gs->write_pos + 2) != msglen) {
return;
write_all(gs->write_fd, &belen, sizeof(belen));
write_all(gs->write_fd, msg, msglen);
} else
gs->write_pos += 2 + msglen;
}
const u8 *gossip_store_read_next(const tal_t *ctx, struct gossip_store *gs)
@@ -60,22 +54,29 @@ const u8 *gossip_store_read_next(const tal_t *ctx, struct gossip_store *gs)
u8 *msg;
/* Did we already reach the end of the gossip_store? */
if (gs->read_fd == -1)
if (gs->read_pos == -1)
return NULL;
/* Can we read one message? */
if (!read_all(gs->read_fd, &belen, sizeof(belen))) {
gs->read_fd = -1;
if (pread(gs->fd, &belen, sizeof(belen), gs->read_pos) != 2) {
gs->read_pos = -1;
return NULL;
}
msglen = be16_to_cpu(belen);
msg = tal_arr(ctx, u8, msglen);
if (!read_all(gs->read_fd, msg, msglen))
status_failed(
STATUS_FAIL_INTERNAL_ERROR,
"Short read from gossip-store, expected lenght %d", msglen);
if (!pread(gs->fd, msg, msglen, gs->read_pos + 2)) {
status_trace("Short read from gossip-store, expected lenght %d",
msglen);
/* Reset write_pos to truncate this message and disable future
* reads */
gs->write_pos = gs->read_pos;
gs->read_pos = -1;
ftruncate(gs->fd, gs->write_pos);
} else
gs->read_pos += 2 + msglen;
return msg;
}