follow mode for inotify_watch

Collaboration diagram for follow mode for inotify_watch:

Functions
void	followInotifyWatchRequestProvider::followStream (std::istream &stream) override

Detailed Description

The InotifyWatch request provider takes the output of The inotify_watch command. to create copy requests.

The format of the inofify watch output is:

<cmd> <timestamp> <filename>

<cmd> is the two-character command, valid are cp to copy a file, rm to remove a file and mv to move (rename) a file. <timestamp> is a decimal double value as seconds since the epoch of the time that the event leading to the request happened, i.e. was seen by inotify_watch. <filename> is the filename of the file to be copied/renamed/deleted, relative to the working directory. In the case of the mv command an additional line with the move target follows.

The end-of-line mark is by default the newline character, but if the -0 option is given it's the NUL character.

ig is a special tag for keepalive messages, which are ignored. They are needed to keep a ssh session from the inotify_watch node to the ewmscp node open.

Because some files tend to be changed quickly after a first close-after-write they should be processed in a delayed queue.

Function Documentation

followStream()

void followInotifyWatchRequestProvider::followStream ( std::istream &  stream )

overrideprivatevirtual

Implements followRequestProvider.

Definition at line 38 of file followInotifyWatchRequestProvider.cpp.

                                                                       {
    char delimiter = nullDelimiter ? '\0' : '\n';
    std::string line;
 
    while (stream) {
        if (stopRequest::Requested()) {
            errMsg::emit(errMsg::level::info, errMsg::location(),
                         "request provider", "stop request received"
                         , "ignoring further requests");
            break;
        }
        char cmdbuff[4] = {0, 0, 0, 0};
        stream.read(cmdbuff, 3);
        auto readTime = copyRequest::clock_type::now();
        if (stream.eof()) {
            break;
        }
 
        double timestampAsDouble;
        stream >> timestampAsDouble;
        auto timestamp = copyRequest::clock_type::time_point(std::chrono::duration_cast<copyRequest::clock_type::duration>(std::chrono::duration<double>(timestampAsDouble)));
        stream.ignore(); // skip one character after timestamp
        std::getline(stream, line, delimiter);
 
        if (strcmp(cmdbuff, "ig ") == 0) { // ignore this line, to be used as keepalive
            continue;
        }
 
        if (strcmp(cmdbuff, "mv ") == 0) { // special case move...
            std::string target;
            std::getline(stream, target, delimiter);
            std::string fromPath;
            auto mapEntryD = getDstPath(line, fromPath);
            std::string dstPath;
            auto mapEntryS = getDstPath(target, dstPath);
            handleMove(target, dstPath, fromPath, line, mapEntryD, timestamp);
        } else {
            auto requestForRemoval = strcmp(cmdbuff, "rm ") == 0;
            std::string dstPath;
            auto mapEntry = getDstPath(line, dstPath);
 
            handleOther(line, dstPath, mapEntry, timestamp, requestForRemoval);
        }
        auto enqueueDoneTime = copyRequest::clock_type::now();
        copyRequest::base::tEnqueueStat.addValue(enqueueDoneTime - readTime);
 
    }
}

References statCollector::typed< T >::addValue(), errMsg::emit(), requestProvider::getDstPath(), followRequestProvider::handleMove(), followRequestProvider::handleOther(), errMsg::info, followRequestProvider::nullDelimiter, stopRequest::Requested(), and copyRequest::base::tEnqueueStat.

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