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9a5f0093f2
Summary: Introduce a new ScribeLogger class that spawns and maintains a process. Log messages are newline-delimited and written to the process's stdin. If the process stops responding or responds too slowly, log messages are dropped. Reviewed By: pkaush Differential Revision: D17777215 fbshipit-source-id: c998d10c73fc103122d69ae19c5d84f58b7939d2
78 lines
2.0 KiB
C++
78 lines
2.0 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#pragma once
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#include <folly/Subprocess.h>
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#include <folly/Synchronized.h>
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#include <list>
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#include "eden/fs/telemetry/ScribeLogger.h"
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namespace facebook {
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namespace eden {
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/**
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* SubprocessScribeLogger manages an external unix process and asynchronously
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* forwards newline-delimited messages to its stdin.
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*/
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class SubprocessScribeLogger : public ScribeLogger {
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public:
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/**
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* Launch `executable` with `category` as the first argument.
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*/
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SubprocessScribeLogger(const char* executable, folly::StringPiece category);
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/**
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* Launch the process specified at argv[0] with the given argv, and forward
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* its stdout to `stdoutFd`, if non-negative. Otherwise, output goes to
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* /dev/null.
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*/
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explicit SubprocessScribeLogger(
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const std::vector<std::string>& argv,
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int stdoutFd = -1);
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/**
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* Waits for the managed process to exit. If it is hung and doesn't complete,
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* terminates the process. Either way, this destructor will completed within a
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* bounded amount of time.
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*/
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~SubprocessScribeLogger();
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/**
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* Forwards a log message to the external process. Must not contain newlines,
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* since that is how the process distinguishes between messages.
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*
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* If the writer process is not keeping up, messages are dropped.
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*/
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void log(std::string message) override;
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using ScribeLogger::log;
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private:
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void closeProcess();
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void writerThread();
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struct State {
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bool shouldStop = false;
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bool didStop = false;
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/// Sum of sizes of queued messages.
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size_t totalBytes = 0;
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/// Invariant: empty if didStop is true
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std::list<std::string> messages;
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};
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folly::Subprocess process_;
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std::thread writerThread_;
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folly::Synchronized<State, std::mutex> state_;
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std::condition_variable newMessageOrStop_;
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std::condition_variable allMessagesWritten_;
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};
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} // namespace eden
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} // namespace facebook
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