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src/sydra/compat/log.zig

Purpose​

Records SQL→sydraQL translation events as JSON Lines (JSONL) written to stderr, and updates global translation counters.

This is intended for:

  • observing translation behavior in real traffic
  • collecting samples for debugging and compatibility testing

Used by​

Public API​

pub const Recorder = struct { ... }​

Fields​

  • enabled: bool = true
  • sample_every: u32 = 1
    • 1 records every event.
    • N records approximately one out of every N calls (starting with the first call).
  • counter: std.atomic.Value(u64) used to implement sampling.

pub fn shouldRecord(self: *Recorder) bool​

  • Returns false when enabled is false.
  • Otherwise increments counter (seq-cst) and returns true when:
    • prev % sample_every == 0
shouldRecord sampling (from src/sydra/compat/log.zig)
pub fn shouldRecord(self: *Recorder) bool {
    if (!self.enabled) return false;
    const prev = self.counter.fetchAdd(1, .seq_cst);
    return (prev % @as(u64, self.sample_every)) == 0;
}

pub fn record(self: *Recorder, sql, translated, used_cache, fell_back, duration_ns) void​

Always updates global counters (even when sampling drops emission):

  • fell_back == true → stats.global().noteFallback()
  • fell_back == false → stats.global().noteTranslation()
  • used_cache == true → stats.global().noteCacheHit()

Then, if shouldRecord() is true, emits a JSON object to stderr and appends a newline.

JSON schema (one line per event):

{
  "ts": 1734144000000,
  "event": "compat.translate",
  "sql": "SELECT 1",
  "sydraql": "FROM ...",
  "cache": false,
  "fallback": false,
  "duration_ns": 123456
}

Notes:

  • ts uses std.time.milliTimestamp() (milliseconds).
  • Writer errors are ignored (the function catch returns frequently).
  • Emission uses a small stack buffer ([512]u8) for stderr writes.
record() JSONL emission (excerpt)
jw.beginObject() catch return;
jw.objectField("ts") catch return;
jw.write(std.time.milliTimestamp()) catch return;
jw.objectField("event") catch return;
jw.write("compat.translate") catch return;
jw.objectField("sql") catch return;
jw.write(sql) catch return;
jw.objectField("sydraql") catch return;
jw.write(translated) catch return;
jw.objectField("cache") catch return;
jw.write(used_cache) catch return;
jw.objectField("fallback") catch return;
jw.write(fell_back) catch return;
jw.objectField("duration_ns") catch return;
jw.write(duration_ns) catch return;
jw.endObject() catch return;
stderr_state.interface.writeAll("\n") catch {};

pub fn global() *Recorder​

Returns a pointer to a file-scoped default_recorder.