Fault tolerance #39
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Fault tolerance #39
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With a supervisor for the client processes, an ered instance survives a crash of an ered_client process. New problems arise: Commands issued while the process is restarting hangs forever and async commands get no response.
The ered process keeps track of pending commands (but not async commands) and with a monitor on each client process, ered can reply with an error if the client process crashes. Then the client is restarted by the supervisor and ered recovers.
bjosv
reviewed
Feb 21, 2024
bjosv
reviewed
Feb 21, 2024
Not that I noticed. We don't have benchmarks... |
zuiderkwast
commented
Feb 21, 2024
bjosv
reviewed
Feb 21, 2024
Co-authored-by: Björn Svensson <[email protected]>
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This change adds a supervisor for client processes, so a client process can crash without affecting the other client processes or the ered instance. (An ered client may crash e.g. due to a bug in OTP's TLS implementation.)
To keep track of missing or dead client processes, the ered process manages monitors to all ered_client processes, so it can properly return errors to commands handled by a crashed client process.
ered:command/3,4returns a value in all situations.ered:command_async/4does not always return a value though. Specifically, if the client process crashes while handling the command, the reply callback function will never be called.Fixes #1.