zircon/system/fidl/fuchsia-logger/logger.fidl

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.logger;

using zx;

enum LogLevelFilter : int8 {
    NONE = -1;
    INFO = 0;
    WARN = 1;
    ERROR = 2;
    FATAL = 3;
};

// Max tags that can be passed to filter by listener.
const uint8 MAX_TAGS = 5;

// Max tag length that can be passed to filter by listener.
const uint8 MAX_TAG_LEN_BYTES = 63;

struct LogFilterOptions {
    bool filter_by_pid;
    uint64 pid;

    bool filter_by_tid;
    uint64 tid;

    // If more than zero, logs would be filtered based on verbosity and
    // `min_severity` would be ignored.
    uint8 verbosity;

    LogLevelFilter min_severity;

    // If non-empty, return all messages which contain at least one specified
    // tag.  If empty, messages will not be filtered by tag.
    // Passed tags should not be more than `MAX_TAG_LEN_BYTES` bytes in length
    // and max tags can be `MAX_TAGS`.
    // Listener would be discarded if the limit is not followed.
    vector<string:MAX_TAG_LEN_BYTES>:MAX_TAGS tags;
};

// Max tags that will be attached to a LogMessage.
const uint8 MAX_TAGS_PER_LOG_MESSAGE = 5;

// Max byte size for message payload.
// TODO(anmittal): Increase it when zircon sockets are able to support a higher
// buffer.
const uint32 MAX_DATAGRAM_LEN_BYTES = 2032;

struct LogMessage {
    uint64 pid;
    uint64 tid;
    // Nanoseconds since the system was powered on, aka ZX_CLOCK_MONOTONIC.
    // https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_get.md#supported-clock-ids
    zx.time time;
    int32 severity;

    // See //zircon/system/ulib/syslog/include/syslog/wire_format.h. As messages
    // can be served out of order, this should only be logged if more than last
    // count.
    uint32 dropped_logs;
    vector<string:MAX_TAG_LEN_BYTES>:MAX_TAGS_PER_LOG_MESSAGE tags;
    string:MAX_DATAGRAM_LEN_BYTES msg;
};

// Interface for LogListener to register to listen to logs.
[Discoverable]
protocol Log {
    // Listens to new log entries by calling Log() on `log_listener`.
    // A null `options` indicates no filtering is requested.
    Listen(LogListener log_listener, LogFilterOptions? options);

    // Dumps all cached logs by calling LogMany() followed by Done() on
    // `log_listener`.
    // A null `options` indicates no filtering is requested.
    DumpLogs(LogListener log_listener, LogFilterOptions? options);
};

// Interface to get and listen to socket from syslogger
[Discoverable]
protocol LogSink {
    // Client connects to send logs over socket
    Connect(handle<socket> socket);
};

/// Max log bytes per call to a listener
const uint64 MAX_LOG_MANY_SIZE_BYTES = 16384;

protocol LogListener {
    // Called for single messages.
    Log(LogMessage log);

    // Called when `Log` service is serving cached logs.
    // Max logs size per call is `MAX_LOG_MANY_SIZE_BYTES` bytes.
    LogMany(vector<LogMessage>:MAX log);

    // Called in the case `DumpLogs()` function of `Log` service was called and
    // all cached logs have been dispatched to this listener.
    Done();
};