README.md

Background Worker Test Infrastructure

This directory contains mocks and hooks to enable testing of timescale background workers. There are three main components: a counter-based timer used to test the scheduler in a deterministic manner; a scheduler that inserts test shims to the background worker and understands the tests we will run; and shims to dynamically set time and intercept background worker output.

Output

Background workers started by the test scheduler contain a hook storing all elog and ereport output in the table

public.bgw_log(
    msg_no INT,
    mock_time BIGINT,
    application_name TEXT,
    msg TEXT,
)

which must be created in order for tests to check background worker output. msg_no contains which message this was in the total-order of all background worker messages sent since the table was created; mock_time is the virtualized timestamp ([see that section](## Timer)) at which the message was written; application_name the name of the application that wrote the message; msg is the messgage string itself.

See log.c for more detail.

(We want to print more data from ErrorData at a later date)

Timer

We virtualize the timer to allow deterministic execution by tests. Our timer store a virtual microsecond counter in shared memory, backround processes can read this counter to determine the current time. The scheduler can "wait" on this timer which optionally waits for a process to finish and updates the counter to the waited time. The timer can be reset manually (for instance, to allow multiple tests in one file) with ts_bgw_params_reset_time).

See timer_mock.c for more detail.

Configuration

Settings and the timer for background worker tests are stored in shared memory. This memory segment must be created with ts_bgw_params_create before use.

see params.c and params.h for more detail.