On 9/19/2024 8:02 AM, Purna Pavan Chandra Aekkaladevi wrote:
Implement `chReadProcessEvents` and `chProcessEvents` to read events from
event monitor FIFO file and parse them accordingly.
Signed-off-by: Purna Pavan Chandra Aekkaladevi <paekkaladevi@xxxxxxxxxxxxxxxxxxx>
Co-authored-by: Vineeth Pillai <viremana@xxxxxxxxxxxxxxxxxxx>
---
src/ch/ch_events.c | 142 +++++++++++++++++++++++++++++++++++++++++++-
src/ch/ch_events.h | 2 +
src/ch/ch_monitor.h | 6 ++
3 files changed, 149 insertions(+), 1 deletion(-)
diff --git a/src/ch/ch_events.c b/src/ch/ch_events.c
index 851fbc9f26..a028f9813e 100644
--- a/src/ch/ch_events.c
+++ b/src/ch/ch_events.c
@@ -28,6 +28,142 @@
VIR_LOG_INIT("ch.ch_events");
Please add a comment here with a sample event here for reference.
+static int virCHProcessEvents(virCHMonitor *mon)
+{
+ char *buf = mon->event_buffer.buffer;
+ ssize_t sz = mon->event_buffer.buf_fill_sz;
+ virJSONValue *obj = NULL;
+ int blocks = 0;
+ size_t i = 0;
+ char *json_start;
+ ssize_t start_index = -1;
+ ssize_t end_index = -1;
+ char tmp;
+ int ret = 0;
+
+ while (i < sz) {
+ if (buf[i] == '{') {
+ blocks++;
+ if (blocks == 1)
+ start_index = i;
+ } else if (buf[i] == '}' && blocks > 0) {
+ blocks--;
+ if (blocks == 0) {
+ // valid json document
+ end_index = i;
+
+ /*
+ * We may hit a corner case where a valid JSON
+ * doc happens to end right at the end of the buffer.
+ * virJSONValueFromString needs '\0' end the JSON doc.
+ * So we need to adjust the buffer accordingly.
+ */
+ if (end_index == CH_EVENT_BUFFER_SZ - 1) {
+ if (start_index == 0) {
+ /*
+ * We have a valid JSON doc same as the buffer
+ * size. As per protocol, max JSON doc should be
+ * less than the buffer size. So this is an error.
+ * Ignore this JSON doc.
+ */
+ VIR_WARN("Invalid JSON doc size. Expected <= %d",
+ CH_EVENT_BUFFER_SZ);
+ start_index = -1;
+ ret = -1;
+ break;
+ }
+
+ /*
+ * Move the valid JSON doc to the start of the buffer so
+ * that we can safely fit a '\0' at the end.
+ */
+ memmove(buf, buf+start_index, end_index-start_index+1);
+ end_index -= start_index;
+ start_index = 0;
+ }
+
+ // temporarily null terminate the JSON doc
+ tmp = buf[end_index + 1];
+ buf[end_index + 1] = '\0';
+ json_start = buf + start_index;
+
+ if ((obj = virJSONValueFromString(json_start))) {
+ /* Process the event string (obj) here */
+ virJSONValueFree(obj);
+ } else {
+ VIR_WARN("Invalid JSON event doc: %s", json_start);
+ ret = -1;
+ }
+
+ // replace the original character
+ buf[end_index + 1] = tmp;
+ start_index = -1;
+ }
+ }
+
+ i++;
+ }
+
+ if (start_index == -1) {
+ // We have processed all the JSON docs in the buffer.
+ mon->event_buffer.buf_fill_sz = 0;
+ } else if (start_index > 0) {
+ // We have an incomplete JSON doc at the end of the buffer.
+ // Move it to the start of the buffer.
+ mon->event_buffer.buf_fill_sz = sz - start_index;
+ memmove(buf, buf+start_index, mon->event_buffer.buf_fill_sz);
+ }
+
+ return ret;
+}
+
+static void virCHReadProcessEvents(virCHMonitor *mon,
+ int event_monitor_fd)
+{
+ size_t max_sz = CH_EVENT_BUFFER_SZ;
To avoid the corner case in virCHProcessEvents where the event ends
at end of buffer, you can set
max_sz = CH_EVENT_BUFFER_SZ -1;
This ensures there is always space for a Null char at the end.
+ char *buf = mon->event_buffer.buffer;
+ virDomainObj *vm = mon->vm;
+ bool incomplete = false;
+ size_t sz = 0;
+
+ memset(buf, 0, max_sz);
+ do {
+ ssize_t ret;
+
+ ret = read(event_monitor_fd, buf + sz, max_sz - sz);
+ if (ret == 0 || (ret < 0 && errno == EINTR)) {
+ g_usleep(G_USEC_PER_SEC);
+ continue;
+ } else if (ret < 0) {
+ /*
+ * We should never reach here. read(2) says possible errors
+ * are EINTR, EAGAIN, EBADF, EFAULT, EINVAL, EIO, EISDIR
+ * We handle EINTR gracefully. There is some serious issue
+ * if we encounter any of the other errors(either in our code
+ * or in the system). Better to bail out.
+ */
+ VIR_ERROR(_("Failed to read ch events!: %1$s"), g_strerror(errno));
+ VIR_FORCE_CLOSE(event_monitor_fd);
+ abort();
+ }
+
+ sz += ret;
+ mon->event_buffer.buf_fill_sz = sz;
+
+ if (virCHProcessEvents(mon) < 0)
+ VIR_WARN("Failed to parse and process events");
+
+ if (mon->event_buffer.buf_fill_sz != 0)
+ incomplete = true;
+ else
+ incomplete = false;
+ sz = mon->event_buffer.buf_fill_sz;
+
+ } while (virDomainObjIsActive(vm) && (sz < max_sz) && incomplete);
+
+ return;
+}
+
static void virCHEventHandlerLoop(void *data)
{
virCHMonitor *mon = data;
@@ -51,6 +187,9 @@ static void virCHEventHandlerLoop(void *data)
}
VIR_DEBUG("Opened the event monitor FIFO(%s)", mon->eventmonitorpath);
+ mon->event_buffer.buffer = g_malloc_n(sizeof(char), CH_EVENT_BUFFER_SZ);
+ mon->event_buffer.buf_fill_sz = 0;
+
/*
* We would need to wait until VM is initialized.
*/
@@ -59,9 +198,10 @@ static void virCHEventHandlerLoop(void *data)
while (g_atomic_int_get(&mon->event_handler_stop) == 0) {
VIR_DEBUG("Reading events from event monitor file...");
- /* Read and process events here */
+ virCHReadProcessEvents(mon, event_monitor_fd);
}
+ g_free(mon->event_buffer.buffer);
VIR_FORCE_CLOSE(event_monitor_fd);
virObjectUnref(vm);
diff --git a/src/ch/ch_events.h b/src/ch/ch_events.h
index 4c8a48231d..2e9cdf03bb 100644
--- a/src/ch/ch_events.h
+++ b/src/ch/ch_events.h
@@ -22,5 +22,7 @@
#include "ch_monitor.h"
+#define CH_EVENT_BUFFER_SZ PIPE_BUF
+
int virCHStartEventHandler(virCHMonitor *mon);
void virCHStopEventHandler(virCHMonitor *mon);
diff --git a/src/ch/ch_monitor.h b/src/ch/ch_monitor.h
index 878a185f29..6b4045d300 100644
--- a/src/ch/ch_monitor.h
+++ b/src/ch/ch_monitor.h
@@ -99,6 +99,12 @@ struct _virCHMonitor {
virThread event_handler_thread;
int event_handler_stop;
+ struct {
+ // Buffer to hold the data read from pipe
Please replace all `//` comments with `/**/`. This is the preferred
comment style in Libvirt.
+ char *buffer;
+ // Size of the data read from pipe in buffer
nit: "Size of the data read from pipe into buffer"
+ size_t buf_fill_sz;
+ } event_buffer;
pid_t pid;
--
Regards,
Praveen K Paladugu
