From: Jeff Hostetler <jeffhost@xxxxxxxxxxxxx>
Teach fsmonitor--daemon to create token-ids and define the
overall token naming scheme.
Signed-off-by: Jeff Hostetler <jeffhost@xxxxxxxxxxxxx>
---
builtin/fsmonitor--daemon.c | 108 +++++++++++++++++++++++++++++++++++-
1 file changed, 107 insertions(+), 1 deletion(-)
diff --git a/builtin/fsmonitor--daemon.c b/builtin/fsmonitor--daemon.c
index 16252487240a..2d25e36601fe 100644
--- a/builtin/fsmonitor--daemon.c
+++ b/builtin/fsmonitor--daemon.c
@@ -149,6 +149,112 @@ static int do_as_client__send_flush(void)
return 0;
}
+/*
+ * Requests to and from a FSMonitor Protocol V2 provider use an opaque
+ * "token" as a virtual timestamp. Clients can request a summary of all
+ * created/deleted/modified files relative to a token. In the response,
+ * clients receive a new token for the next (relative) request.
+ *
+ *
+ * Token Format
+ * ============
+ *
+ * The contents of the token are private and provider-specific.
+ *
+ * For the built-in fsmonitor--daemon, we define a token as follows:
+ *
+ * "builtin" ":" <token_id> ":" <sequence_nr>
+ *
+ * The <token_id> is an arbitrary OPAQUE string, such as a GUID,
+ * UUID, or {timestamp,pid}. It is used to group all filesystem
+ * events that happened while the daemon was monitoring (and in-sync
+ * with the filesystem).
+ *
+ * Unlike FSMonitor Protocol V1, it is not defined as a timestamp
+ * and does not define less-than/greater-than relationships.
+ * (There are too many race conditions to rely on file system
+ * event timestamps.)
+ *
+ * The <sequence_nr> is a simple integer incremented for each event
+ * received. When a new <token_id> is created, the <sequence_nr> is
+ * reset to zero.
+ *
+ *
+ * About Token Ids
+ * ===============
+ *
+ * A new token_id is created:
+ *
+ * [1] each time the daemon is started.
+ *
+ * [2] any time that the daemon must re-sync with the filesystem
+ * (such as when the kernel drops or we miss events on a very
+ * active volume).
+ *
+ * [3] in response to a client "flush" command (for dropped event
+ * testing).
+ *
+ * [4] MAYBE We might want to change the token_id after very complex
+ * filesystem operations are performed, such as a directory move
+ * sequence that affects many files within. It might be simpler
+ * to just give up and fake a re-sync (and let the client do a
+ * full scan) than try to enumerate the effects of such a change.
+ *
+ * When a new token_id is created, the daemon is free to discard all
+ * cached filesystem events associated with any previous token_ids.
+ * Events associated with a non-current token_id will never be sent
+ * to a client. A token_id change implicitly means that the daemon
+ * has gap in its event history.
+ *
+ * Therefore, clients that present a token with a stale (non-current)
+ * token_id will always be given a trivial response.
+ */
+struct fsmonitor_token_data {
+ struct strbuf token_id;
+ struct fsmonitor_batch *batch_head;
+ struct fsmonitor_batch *batch_tail;
+ uint64_t client_ref_count;
+};
+
+static struct fsmonitor_token_data *fsmonitor_new_token_data(void)
+{
+ static int test_env_value = -1;
+ static uint64_t flush_count = 0;
+ struct fsmonitor_token_data *token;
+
+ token = (struct fsmonitor_token_data *)xcalloc(1, sizeof(*token));
+
+ strbuf_init(&token->token_id, 0);
+ token->batch_head = NULL;
+ token->batch_tail = NULL;
+ token->client_ref_count = 0;
+
+ if (test_env_value < 0)
+ test_env_value = git_env_bool("GIT_TEST_FSMONITOR_TOKEN", 0);
+
+ if (!test_env_value) {
+ struct timeval tv;
+ struct tm tm;
+ time_t secs;
+
+ gettimeofday(&tv, NULL);
+ secs = tv.tv_sec;
+ gmtime_r(&secs, &tm);
+
+ strbuf_addf(&token->token_id,
+ "%"PRIu64".%d.%4d%02d%02dT%02d%02d%02d.%06ldZ",
+ flush_count++,
+ getpid(),
+ tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+ tm.tm_hour, tm.tm_min, tm.tm_sec,
+ (long)tv.tv_usec);
+ } else {
+ strbuf_addf(&token->token_id, "test_%08x", test_env_value++);
+ }
+
+ return token;
+}
+
static ipc_server_application_cb handle_client;
static int handle_client(void *data, const char *command,
@@ -330,7 +436,7 @@ static int fsmonitor_run_daemon(void)
pthread_mutex_init(&state.main_lock, NULL);
state.error_code = 0;
- state.current_token_data = NULL;
+ state.current_token_data = fsmonitor_new_token_data();
state.test_client_delay_ms = 0;
/* Prepare to (recursively) watch the <worktree-root> directory. */
--
gitgitgadget
