[FEATURE] Micrometer support for Oracle UCP

[simasch]

When using the standard HikariCP Micrometer is automatically enabled.
It would be helpful to have that with UCP as well.

Currently I do this:

public class UcpPoolMetrics implements MeterBinder {

    private final PoolDataSource poolDataSource;

    private final Tags tags;

    public UcpPoolMetrics(PoolDataSource poolDataSource) {
        this.poolDataSource = poolDataSource;
        var poolName = poolDataSource.getConnectionPoolName();
        this.tags = Tags.of("pool", poolName != null ? poolName : "ucp");
    }

    @Override
    public void bindTo(MeterRegistry registry) {
        gauge(registry, "ucp.connections", "Total connections in the pool",
                UniversalConnectionPoolStatistics::getTotalConnectionsCount);
        gauge(registry, "ucp.connections.active", "Borrowed (in use) connections",
                UniversalConnectionPoolStatistics::getBorrowedConnectionsCount);
        gauge(registry, "ucp.connections.idle", "Available (idle) connections",
                UniversalConnectionPoolStatistics::getAvailableConnectionsCount);
        gauge(registry, "ucp.connections.pending", "Threads waiting for a connection",
                UniversalConnectionPoolStatistics::getPendingRequestsCount);
        gauge(registry, "ucp.connections.peak", "Peak connection count since pool start",
                UniversalConnectionPoolStatistics::getPeakConnectionsCount);

        Gauge.builder("ucp.connections.min", this.poolDataSource, PoolDataSource::getMinPoolSize)
            .tags(this.tags)
            .description("Configured minimum pool size")
            .register(registry);
        Gauge.builder("ucp.connections.max", this.poolDataSource, PoolDataSource::getMaxPoolSize)
            .tags(this.tags)
            .description("Configured maximum pool size")
            .register(registry);

        // Not named "created": OpenMetrics reserves the _created suffix, so a meter named
        // ucp.connections.created would collide with the ucp.connections gauge.
        counter(registry, "ucp.connections.opened", "Physical connections created",
                UniversalConnectionPoolStatistics::getConnectionsCreatedCount);
        counter(registry, "ucp.connections.closed", "Physical connections closed",
                UniversalConnectionPoolStatistics::getConnectionsClosedCount);
        counter(registry, "ucp.connections.abandoned", "Connections reclaimed as abandoned",
                UniversalConnectionPoolStatistics::getAbandonedConnectionsCount);
        counter(registry, "ucp.connections.timeout", "Failed connection borrow attempts (wait failures)",
                UniversalConnectionPoolStatistics::getCumulativeFailedConnectionWaitCount);

        FunctionTimer
            .builder("ucp.connections.acquire", this.poolDataSource,
                    ds -> (long) statistic(ds, UniversalConnectionPoolStatistics::getCumulativeConnectionBorrowedCount),
                    ds -> statistic(ds, UniversalConnectionPoolStatistics::getCumulativeConnectionWaitTime),
                    TimeUnit.MILLISECONDS)
            .tags(this.tags)
            .description("Time spent waiting to borrow a connection")
            .register(registry);
        FunctionTimer
            .builder("ucp.connections.usage", this.poolDataSource,
                    ds -> (long) statistic(ds, UniversalConnectionPoolStatistics::getCumulativeConnectionReturnedCount),
                    ds -> statistic(ds, UniversalConnectionPoolStatistics::getCumulativeConnectionUseTime),
                    TimeUnit.MILLISECONDS)
            .tags(this.tags)
            .description("Time connections spend borrowed before being returned")
            .register(registry);
    }

    private void gauge(MeterRegistry registry, String name, String description,
            ToDoubleFunction<UniversalConnectionPoolStatistics> value) {
        Gauge.builder(name, this.poolDataSource, ds -> statistic(ds, value))
            .tags(this.tags)
            .description(description)
            .register(registry);
    }

    private void counter(MeterRegistry registry, String name, String description,
            ToDoubleFunction<UniversalConnectionPoolStatistics> value) {
        FunctionCounter.builder(name, this.poolDataSource, ds -> statistic(ds, value))
            .tags(this.tags)
            .description(description)
            .register(registry);
    }

    /**
     * UCP returns no statistics object before the pool has been started.
     */
    private static double statistic(PoolDataSource poolDataSource,
            ToDoubleFunction<UniversalConnectionPoolStatistics> value) {
        var statistics = poolDataSource.getStatistics();
        return statistics != null ? value.applyAsDouble(statistics) : 0;
    }

}

[anders-swanson]

Hey, thanks for raising this! We'll look to add this feature to our UCP instrumentation.

[anders-swanson]

Working on this in #317