features/changelog : historical journal consumption.

Facilitates Glusterfs with the ability to detect file-operations
happened in past by scanning the back-end(brick-level) glusterfs
journal (changelog).

Design:
  * List of changelogs produces in one perfectly running session are
    stored in htime file which also holds necessary information about
    the session start and end time.
  * Involves fixed sized seeks to identify N'th changelog in the list.
  * Requires O(log n), (where n is number of changelogs in the list),
    time to identify the end changelog for the given start-end time
    interval.

Currently the background processing of changelogs is sub optimal. BZ
1097041 tracks the development effort.

For complete design, refer the below link:
http://lists.nongnu.org/archive/html/gluster-devel/2014-02/msg00206.html

Change-Id: I27e49f75e492e843084d0ecaf9130224d08462a0
BUG: 1091961
Signed-off-by: Ajeet Jha <ajha@redhat.com>
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Signed-off-by: Ajeet Jha <ajha@redhat.com>
Reviewed-on: http://review.gluster.org/6930
Reviewed-by: Kotresh HR <khiremat@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/xlators/features/changelog/lib/src/gf-changelog-helpers.h b/xlators/features/changelog/lib/src/gf-changelog-helpers.h
index 2d545da9e82..218896b86e7 100644
--- a/xlators/features/changelog/lib/src/gf-changelog-helpers.h
+++ b/xlators/features/changelog/lib/src/gf-changelog-helpers.h
@@ -24,6 +24,7 @@
 #define GF_CHANGELOG_PROCESSED_DIR  ".processed"
 #define GF_CHANGELOG_PROCESSING_DIR ".processing"
 #define GF_CHANGELOG_HISTORY_DIR    ".history"
+#define TIMESTAMP_LENGTH 10
 
 #ifndef MAXLINE
 #define MAXLINE 4096
@@ -72,8 +73,45 @@ typedef struct gf_changelog {
 
         /* Holds gfc for History API */
         struct gf_changelog *hist_gfc;
+
+        /* holds 0 done scanning, 1 keep scanning and -1 error */
+        int hist_done;
 } gf_changelog_t;
 
+typedef struct gf_changelog_history_data {
+        int           len;
+
+        int           htime_fd;
+
+        /* parallelism count */
+        int           n_parallel;
+
+        /* history from, to indexes */
+        unsigned long from;
+        unsigned long to;
+} gf_changelog_history_data_t;
+
+typedef struct gf_changelog_consume_data {
+        /** set of inputs */
+
+        /* fd to read from */
+        int             fd;
+
+        /* from @offset */
+        off_t           offset;
+
+        xlator_t       *this;
+        gf_changelog_t *gfc;
+
+        /** set of outputs */
+
+        /* return value */
+        int retval;
+
+        /* journal processed */
+        char changelog[PATH_MAX];
+} gf_changelog_consume_data_t;
+
 int
 gf_changelog_notification_init (xlator_t *this, gf_changelog_t *gfc);
 
@@ -98,4 +136,11 @@ gf_ftruncate (int fd, off_t length);
 off_t
 gf_lseek (int fd, off_t offset, int whence);
 
+int
+gf_changelog_consume (xlator_t *this,
+                      gf_changelog_t *gfc,
+                      char *from_path, gf_boolean_t no_publish);
+int
+gf_changelog_publish (xlator_t *this, gf_changelog_t *gfc, char *from_path);
+
 #endif