On Thu, Sep 26, 2024 at 11:16:37AM -0500, Praveen K Paladugu wrote:
>
>
> 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
> > <[email protected]>
> > Co-authored-by: Vineeth Pillai <[email protected]>
> > ---
> > 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.
>
Sure, will do.
> > +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.
This would be same as what current logic is doing i.e., supporting
events of length less than CH_EVENT_BUFFER_SZ.
Currently, when event length is CH_EVENT_BUFFER_SZ, we warn saying
expected length is <CH_EVENT_BUFFER_SZ. Otherwise, we already have
enough space to additionally terminate with null char.
> > + 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.
>
Will take care of it in V2.
> > + char *buffer;
> > + // Size of the data read from pipe in buffer
> nit: "Size of the data read from pipe into buffer"
Sure
> > + size_t buf_fill_sz;
> > + } event_buffer;
> > pid_t pid;
>
> --
> Regards,
> Praveen K Paladugu
Regards,
Purna Pavan Chandra
