Christian Schwarz 10a14a8c50 [#307] add package trace, integrate it with logging, and adopt it throughout zrepl ... package trace: - introduce the concept of tasks and spans, tracked as linked list within ctx - see package-level docs for an overview of the concepts - **main feature 1**: unique stack of task and span IDs - makes it easy to follow a series of log entries in concurrent code - **main feature 2**: ability to produce a chrome://tracing-compatible trace file - either via an env variable or a `zrepl pprof` subcommand - this is not a CPU profile, we already have go pprof for that - but it is very useful to visually inspect where the replication / snapshotter / pruner spends its time ( fixes #307 ) usage in package daemon/logging: - goal: every log entry should have a trace field with the ID stack from package trace - make `logging.GetLogger(ctx, Subsys)` the authoritative `logger.Logger` factory function - the context carries a linked list of injected fields which `logging.GetLogger` adds to the logger it returns - `logging.GetLogger` also uses package `trace` to get the task-and-span-stack and injects it into the returned logger's fields		2020-05-19 11:30:02 +02:00
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transportmux.go	[#307] add package trace, integrate it with logging, and adopt it throughout zrepl	2020-05-19 11:30:02 +02:00