Re: [PATCH 4/6] ch: events: Read and parse cloud-hypervisor events

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(a)linux.microsoft.com&gt; > Co-authored-by: Vineeth Pillai <viremana(a)linux.microsoft.com&gt; > --- > 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