perf(logger): replace serde_json::json! with zero-allocation write! in logger#1042
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…n logger Commit 3b533a0 introduced serde_json::json!() for JSON log formatting, which allocates a heap Map+Value on every log call and pulled in the tracing-serde crate via the "json" feature of tracing-subscriber, increasing binary size and Lambda init duration. Replace with direct write!/writeln! calls to the tracing Writer plus a small write_json_escaped helper that handles all 6 mandatory JSON escape sequences inline. The output format is identical. Also remove the "json" feature from tracing-subscriber, dropping tracing-serde as a transitive dependency. JIRA: https://datadoghq.atlassian.net/browse/SVLS-8619
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Summary
Root cause: commit 3b533a0 introduced
serde_json::json!()for JSON formatting, adding per-call heap pressure and a new crate dependency that contributes to Lambda init duration regressionJIRA: https://datadoghq.atlassian.net/browse/SVLS-8619
serde_json::json!()inlogger.rswith directwrite!/writeln!calls to the tracingWriter, eliminating two heap allocations (aMap+Value) per log callwrite_json_escapedhelper that handles all 6 mandatory JSON escape sequences inline (",\,\n,\r,\t, U+0000–U+001F)"json"feature fromtracing-subscriber, droppingtracing-serdeas a transitive dependency and reducing binary sizeTest plan