47154eb893c07bfb01d8fe044121048378705e28
[EVA-2020-02.git] / exec / bkgpslog-plan.org
1 * bkgpslog task list
2 ** DONE Add job control for short buffer length
3 CLOSED: [2020-07-02 Thu 16:04]
4 2020-07-02T14:56Z; bktei> File write operations were bundled into a
5 magicWriteBuffer function that is called then detached from the script
6 shell (job control), but the detached job is not tracked by the main
7 script. A problem may arise if two instances of magicWriteBuffer
8 attempt to write to the same tar simultaneously. Two instances of
9 magicWriteBuffer may exist if the buffer length is low (ex: 1 second);
10 the default buffer length of 60 seconds should reduce the probability
11 of a collision but it should be possible for the main script to track
12 the process ID of a magicWriteBuffer() as soon as it detaches and then
13 checking (via ~$!~ as described [[https://bashitout.com/2013/05/18/Ampersands-on-the-command-line.html][here]]) that the process is still alive.
14 2020-07-02T15:23Z; bktei> I found that the Bash ~wait~ built-in can be
15 used to delay processing until a specified job completes. The ~wait~
16 command will pause script execution until all backgrounded processes
17 complete.
18 2020-07-02T16:03Z; bktei> Added ~wait~.
19 ** DONE Rewrite tar initialization function
20 CLOSED: [2020-07-02 Thu 17:23]
21 2020-07-02T17:23Z; bktei> Simplify tar initialization function so
22 VERSION file is used to test appendability of tar as well as to mark
23 when a new session is started.
24 ** DONE Consolidate tar checking/creation into function
25 CLOSED: [2020-07-02 Thu 18:33]
26 2020-07-02T18:33Z; bktei> Simplify how the output tar file's existence
27 is checked and its status as a valid tar file is validated. This was
28 done using a new function ~checkMakeTar~.
29 ** DONE Add VERSION if output tar deleted between writes
30
31 CLOSED: [2020-07-02 Thu 20:22]
32 2020-07-02T20:21Z; bktei> Added bkgpslog-specified function
33 magicWriteVersion() to be called whenever a new time-stamped ~VERSION~
34 file needs to be generated and appended to the output tar file
35 ~PATHOUT_TAR~.
36 ** DONE Rewrite buffer loop to reduce lag between gpspipe runs
37 CLOSED: [2020-07-03 Fri 20:57]
38 2020-07-03T17:10Z; bktei> As is, there is still a 5-6 second lag
39 between when ~gpspipe~ times out at the end of a buffer round and when
40 ~gpspipe~ is called by the subsequent buffer round. I believe this can
41 be reduced by moving variable manipulations inside the
42 asynchronously-executed magicWriteBuffer() function. Ideally, the
43 while loop should look like:
44
45 #+BEGIN_EXAMPLE
46 while( $SECONDS < $SCRIPT_TTL); do
47 gpspipe-r > "$DIR_TMP"/buffer.nmea
48 writeBuffer &
49 done
50 #+END_EXAMPLE
51 2020-07-03T20:56Z; bktei> I simplified it futher to something like
52 this:
53 #+BEGIN_EXAMPLE
54 while( $SECONDS < $SCRIPT_TTL); do
55 writeBuffer &
56 sleep $SCRIPT_TTL
57 done
58 #+END_EXAMPLE
59 Raspberry Pi Zero W shows approximately 71ms of drift per buffer round
60 with 10s buffer.
61 * bkgpslog narrative
62 ** Initialize environment
63 *** Init variables
64 **** Save timeStart (YYYYmmddTHHMMSS±zz)
65 *** Define Functions
66 **** Define Debugging functions
67 **** Define Argument Processing function
68 **** Define Main function
69 ** Run Main Function
70 *** Process Arguments
71 *** Set output encryption and compression option strings
72 *** Check that critical apps and dirs are available, displag missing ones.
73 *** Set lifespans of script and buffer
74 *** Init temp working dir ~DIR_TMP~
75 Make temporary dir in tmpfs dir: ~/dev/shm/$(nonce)..bkgpslog/~ (~DIR_TMP~)
76 *** Initialize ~tar~ archive
77 **** Write ~bkgpslog~ version to ~$DIR_TMP/VERSION~
78 **** Create empty ~tar~ archive in ~DIR_OUT~ at ~PATHOUT_TAR~
79
80 Set output file name to:
81 : PATHOUT_TAR="$DIR_OUT/YYYYmmdd..hostname_location.gz.age.tar"
82 Usage: ~iso8601Period $timeStart $timeEnd~
83
84 **** Append ~VERSION~ file to ~PATHOUT_TAR~
85
86 Append ~$DIR_TMP/VERSION~ to ~PATHOUT_TAR~ via ~tar --append~
87
88 *** Read/Write Loop (Record gps data until script lifespan ends)
89 **** Determine output file paths
90 **** Define GPS conversion commands
91 **** Fill Bash variable buffer from ~gpspipe~
92 **** Process bufferBash, save secured chunk set to ~DIR_TMP~
93 **** Append each secured chunk to ~PATHOUT_TAR~
94 : tar --append --directory=DIR_TMP --file=PATHOUT_TAR $(basename PATHOUT_{NMEA,GPX,KML} )
95 **** Remove secured chunk from ~DIR_TMP~