Examples Collapse

Collapse example

Collapse

This example shows how to collapse repeated log messages.

What it demonstrates

• LogmeD_Collapse(...) / LogmeD_CollapseIgnore(...)
• LogmeI_Collapse(...) / LogmeI_CollapseIgnore(...)
• LogmeW_Collapse(...) / LogmeW_CollapseIgnore(...)
• LogmeE_Collapse(...) / LogmeE_CollapseIgnore(...)
• LogmeC_Collapse(...) / LogmeC_CollapseIgnore(...)
• LogmeD_CollapseEvery(...) / LogmeD_CollapseIgnoreEvery(...)
• LogmeI_CollapseEvery(...) / LogmeI_CollapseIgnoreEvery(...)
• LogmeW_CollapseEvery(...) / LogmeW_CollapseIgnoreEvery(...)
• LogmeE_CollapseEvery(...) / LogmeE_CollapseIgnoreEvery(...)
• LogmeC_CollapseEvery(...) / LogmeC_CollapseIgnoreEvery(...)

Notes

• LogmeX_Collapse(limit, ...) uses the formatted message text as the repeat key.
• LogmeX_CollapseIgnore(ignoreRegex, limit, ...) removes all substrings matching ignoreRegex from the formatted message before comparing it with the previous message.
• LogmeX_CollapseEvery(intervalMs, ...) suppresses matching repeated messages until the interval expires.
• LogmeX_CollapseIgnoreEvery(ignoreRegex, intervalMs, ...) combines time-based collapse with ignored volatile substrings.
• LogmeX_CollapseIgnore(...) and LogmeX_CollapseIgnoreEvery(...) are intended for volatile fields such as request IDs, correlation IDs, timestamps, or counters.
• Ignore variants print the original formatted message. The regular expression is used only for comparison.
• X is one of the usual log levels: D, I, W, E, or C.
• The first message is printed immediately.
• Count-based collapse skips repeated messages from the same macro call site until the repeat counter reaches limit.
• Time-based collapse skips repeated messages from the same macro call site until intervalMs expires.
• Other log messages written by other source lines do not reset that call site's counter.
• The example intentionally writes a normal LogmeI(...) message between calls to LogmeW_Collapse(...) to show this behavior.
• When the count limit is reached or the time interval expires, logme prints one message with the repeat counter and then starts counting again.
• logme does not currently print a final summary for pending suppressed repeats when the log is closed.
• Time-based collapse does not print a pending summary when the repeat key changes. The new key starts a new collapse series.

Repeated sequences and multi-line messages

Collapse works on one formatted message at one macro call site. It does not automatically detect that several different log records form a repeated block.

For a repeated sequence such as MQTT Connecting, Connected, Subscribe, and Disconnected, either collapse each log statement separately, or write one diagnostic message containing embedded \n characters if the whole sequence should be treated as one block.

For messages with changing ids, use _CollapseIgnore or _CollapseIgnoreEvery to remove the volatile part from the comparison key:

LogmeI_CollapseIgnoreEvery(
  R"(\[mqtt [0-9]+\])"
  , 1000
  , "[mqtt %llu] Connecting to MQTT broker"
  , mqttId
);