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bf7d88a027
Full manual diffs (L15, C20, E30, L25, J40, C10 §2, L10, P10, P11, J20, C30, P20, R40, E10) and read-only checks on the shared R1.05 test server. Skills and summaries moved to R1.05; new skill pytools (IM 36K10P40) from docs (no Python on the test server). Issues ISS-132..181; corrections to version-differences (E10, E30, P11, dss_ath_grp_u0104); C10 summary lists the 3 new authorization actions; r105-verification V10-V17. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
85 lines
4 KiB
Markdown
85 lines
4 KiB
Markdown
---
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task: Wait for value or record changes with DSS event notification in a Python script
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version: R1.05
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source: IM 36K10P40-01EN §3.10, §3.11 (stop request), §4 (2nd ed., Feb. 2026); `EVENT_Q_SLOTS` in the installed `dss.sup` (R1.03 and R1.05)
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status: from docs, not tested (no Python on the R1.05 test server)
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---
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# Event notification
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Start from `setup-first-script.md`. The example only reads; it leaves nothing behind when it
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ends (notifications stopped, dataset and connection closed).
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## 1. How it works
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- Request: per record `dss.recordEventNotify(conn, ds, <key>, 'u')` (`u` update, `d` delete),
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or per dataset `dss.datasetEventNotify(conn, ds, 'iud')` (also `i` insert).
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- DSS puts each change in **one queue per client**; the script must **poll** it with
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`dss.eventRead(conn)` → list of dicts `{'ds_name', 'event', 'id', 'record', 'set_hnd'}`
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(`record` = the record after the change, only the fields opened). Empty list = nothing new.
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- If the queue overflows, DSS **empties it** (events lost). Size: `EVENT_Q_SLOTS` in
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`dss.sup` (default 100); poll often and keep the number of watched records reasonable.
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- One request per record; to change the mode, stop it first (`PY_DSS_EVT_NOTIFY_DEF`).
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- Stop with `recordEventStop` / `datasetEventStop`, then close.
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## 2. Example: print value changes of two items
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```python
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import os, sys, time, getpass
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sys.path.insert(0, os.path.join(os.environ['TLS_ROOT_PATH'], 'tls', 'exe'))
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import dss
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ITEMS = ['CI-Eng-Sample.TANK1.LEVEL', 'CI-Eng-Sample.PUMP1.RUNNING'] # or <Section>.<Tag>
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RUN_SECONDS = 60 # 0 = until Ctrl+C
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conn = dss.connect(os.environ.get('CI_USER') or input('User: '),
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os.environ.get('CI_PASSWORD') if 'CI_PASSWORD' in os.environ
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else getpass.getpass('Password: '))
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watched = []
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try:
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ds = dss.openDataset(conn, 'ITEM_VAL', ['NAME', 'ITEM_VALUE', 'STATUS', 'UPDATE_TIME'], 'r')
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try:
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for name in ITEMS:
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dss.recordEventNotify(conn, ds, name, 'u')
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watched.append(name)
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t_end = time.time() + RUN_SECONDS
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try:
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while not RUN_SECONDS or time.time() < t_end:
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time.sleep(1)
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for ev in dss.eventRead(conn):
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r = ev['record']
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print(dss.dateString(conn, r['UPDATE_TIME'], 'GENERAL'),
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r['NAME'], r['ITEM_VALUE'], r['STATUS'])
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except KeyboardInterrupt:
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pass
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finally:
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for name in watched:
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dss.recordEventStop(conn, ds, name)
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dss.closeDataset(conn, ds)
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finally:
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dss.close(conn)
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```
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Expected: one line per value update of the two items (with the sample's live-data feed
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running, `TANK1.LEVEL` changes every few seconds); nothing for unchanged items. Ends after
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60 s or Ctrl+C.
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## 3. Long-running scripts
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- Give the script a fixed BUS name **before** connecting: `dss.busSetName('PYWATCH')`. It can
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then be stopped cleanly from a command prompt with `durstp -p PYWATCH`; inside the script
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this raises `dss.error` with code `PY_DSS_STOP_REQUEST` — catch it, stop the notifications,
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close and exit. Without a name the process is `PYDSS_<number>` (new each run). Check whether
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it runs with `durwfp -p PYWATCH -t 0` (skill `system-management`, `bus-utilities.md`).
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- Instead of `time.sleep` polling, a script that also serves BUS messages can block in
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`dss.busReceive(conn, 'SYNC_WAIT')` (manual §3.11); then events are only read between
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messages.
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- Do not leave test watchers running on a shared or production server.
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## 4. Not tested / to verify
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On a test Core with Python and the sample feed (user): run §2 (expect changes of
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`TANK1.LEVEL`); start it with a BUS name and stop it with `durstp` (expect a clean exit via
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`PY_DSS_STOP_REQUEST`); check whether the R1.05 module still names unnamed scripts
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`PYDSS_<n>` (the `dss.sup` routing `PYDSS*` → `DSSSDAPY` relies on it, while a script with
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its own BUS name such as `PYWATCH` may be routed to a general `DSSSDA` instead, ISS-180).
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