fix(bklog):Fix buffer drift via SECONDS

==Change 1==
Fix drift in when bklog starts reading data via `while read` by
enforcing buffer termination when SECONDS (script variable that
increments every second) rises above a number determined by the
current bufferRound number and bufferTTL.

==Change 2==
Also initially advance SECONDS so it aligns with the remainder of
dividing the current seconds remaining in the day by bufferTTL. The
result should be that, if the user specifies a bufferTTL value that is
a clean fraction of a time element (ex: a bufferTTL of 5 minutes = 300
seconds), then each buffer round should start at a clean fraction of
absolute time with respect to the day (ex: 02:05, 02:10, 02:15,
etc.). This may assist searching through saved files since instead of
files named:

20200714T000019+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T000521+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T001023+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T001525+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T002027+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T002529+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T003031+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T003533+0000--PT5M0S..hostname_location.nmea.gz.age

they will be named something more like:

20200714T000000+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T000500+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T001000+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T001500+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T002000+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T002500+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T003000+0000--PT5M0S..hostname_location.nmea.gz.age
20200714T003500+0000--PT5M0S..hostname_location.nmea.gz.age

==Change 3==

Fix how the ISO-8601 duration string is calculated. Instead of using a
fixed value of `bufferTTL` seconds, record the epoch start and end
times (in seconds since 1970-01-01) of the main data gathering loop
and then calculate the difference. Now, actual deviations in buffer
gathering durations (ex: the first buffer round will likely be shorter
than a normal one) will be accurately represented.

diff --git a/exec/bklog b/exec/bklog
index fbe28e0e651eac8dde57d76e84935fd3ddd4c86e..9b7fd6756c94631afdf08db4182a55c762a20209 100644 (file)
--- a/exec/bklog
+++ b/exec/bklog
@@ -11,7 +11,7 @@ dirTmpDefault="/dev/shm"; # Default parent of working directory
 
 # Script Metadata
 scriptName="bklog";             # Define basename of script file.
-scriptVersion="0.1.24";          # Define version of script.
+scriptVersion="0.1.25";          # Define version of script.
 scriptURL="https://gitlab.com/baltakatei/ninfacyzga-01"; # Define wesite hosting this script.
 scriptTimeStart="$(date +%Y%m%dT%H%M%S.%N)"; # YYYYmmddTHHMMSS.NNNNNNNNN
 scriptHostname=$(hostname);     # Save hostname of system running this script.
@@ -1218,14 +1218,15 @@ magicWriteVersion() {
 } # write version data to pathout_tar via appendArgTar()
 magicProcessWriteBuffer() {
     # Desc: process and write buffer
-    # In : vars: bufferTTL bufferTTL_STR scriptHostname label dir_tmp SECONDS
+    # In : vars: bufferTTL scriptHostname label dir_tmp SECONDS
+    #    : vars: timeBufferStartEpoch timeBufferEndEpoch
     #    : arry: buffer
     # Out: file:(pathout_tar)
     # Depends: Bash 5.0.3, date 8.30, yell(), vbm(), dateTimeShort(),
     ### Note: These arrays should all have the same number of elements:
     ###       pathouts, fileouts, procFileExts, procStrings
     
-    local fn timeBufferStartLong timeBufferStart fileoutBasename
+    local fn timeBufferStartLong timeBufferStart bufferDuration bufferDurationStr fileoutBasename
     local -a fileouts pathouts
     local writeCmd1 writeCmd2 writeCmd3 writeCmd4
 
@@ -1239,12 +1240,17 @@ magicProcessWriteBuffer() {
     
     # Determine file paths (time is start of buffer period)
     ## Calculate start time
-    timeBufferStartLong="$(date --date="$bufferTTL seconds ago" --iso-8601=seconds)" && \
-       vbm "DEBUG :$fn:timeBufferStartLong:$timeBufferStartLong";
+    timeBufferStartLong="$(date --date="@$timeBufferStartEpoch" --iso-8601=seconds)" && \
+       vbm "DEBUG :$fn:timeBufferStartLong:$timeBufferStartLong"; # Note start time in 'date' parsable ISO-8601
     timeBufferStart="$(dateTimeShort "$timeBufferStartLong" )" && \
        vbm "DEBUG :$fn:timeBufferStart:$timeBufferStart"; # Note start time YYYYmmddTHHMMSS+zzzz (no separators)
+    ## Calculate buffer duration string (ISO-8601 duration)
+    bufferDuration="$((timeBufferEndEpoch - timeBufferStartEpoch))" && \
+       vbm "DEBUG :$fn:bufferDuration:$bufferDuration"; # length of time (seconds) stdin was read
+    bufferDurationStr="$(timeDuration "$bufferDuration")" && \
+       vbm "DEBUG :$fn:bufferDurationStr:$bufferDurationStr"; # buffer duration (ISO-8601)
     ## Set common basename
-    fileoutBasename="$timeBufferStart""--""$bufferTTL_STR""..""$scriptHostname""$label" && \
+    fileoutBasename="$timeBufferStart""--""$bufferDurationStr""..""$scriptHostname""$label" && \
        vbm "STATUS:$fn:Set fileoutBasename to:$fileoutBasename";
     ## Determine output file name array
     ### in: fileOutBasename cmd_compress_suffix cmd_encrypt_suffix procFileExts
@@ -1400,8 +1406,13 @@ main() {
     # Perform secondary setup operations
     ## Set script lifespan (scriptTTL from scriptTTL_TE)
     magicSetScriptTTL "$scriptTTL_TE";
-    ## File name substring (ISO-8601 duration from bufferTTL)
-    bufferTTL_STR="$(timeDuration "$bufferTTL")" && vbm "DEBUG :$fn:bufferTTL_STR:$bufferTTL_STR";
+    ## Adjust SECONDS so buffer rounds align with time elements
+    ### Advance SECONDS the remainder seconds for dividend timeUntilNextDay, divisor bufferTTL
+    if [[ "$(timeUntilNextDay)" -gt "$bufferTTL" ]]; then
+       vbm "DEBUG :$fn:SECONDS currently  :$SECONDS";
+       SECONDS="$(( $(timeUntilNextDay) % bufferTTL ))" && \
+           vbm "DEBUG :$fn:SECONDS advanced to:$SECONDS";
+    fi;
     ## Init temp working dir
     try mkdir "$dir_tmp" && vbm "DEBUG :$fn:Working dir created at dir_tmp:$dir_tmp";
     ## Initialize output tar (set pathout_tar)
@@ -1418,12 +1429,16 @@ main() {
     bufferRound=0;
     while [[ $SECONDS -lt "scriptTTL" ]]; do
        vbm "STATUS:$fn:Starting buffer round:$bufferRound";
-       bufferTOD="$((SECONDS + bufferTTL))"; # Set buffer round time-of-death
+       bufferTOD="$(( (1+bufferRound)*bufferTTL ))"; # Set buffer round time-of-death
+       # Note start time of data collection
+       timeBufferStartEpoch="$(date +%s)";
        # Consume stdin to fill buffer until buffer time-of-death (TOD) arrives
        while read -r -t "$bufferTTL" line && [[ $SECONDS -lt "$bufferTOD" ]]; do
            # Append line to buffer array
            buffer+=("$line");
        done;
+       # Note end time of data collection
+       timeBufferEndEpoch="$(date +%s)";
        # Create dir_tmp if missing
        if ! [[ -d "$dir_tmp" ]]; then
            yell "ERROR:$fn:dir_tmp existence failure:$dir_tmp";