Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, QOS.ch. All rights reserved.
This program and the accompanying materials are dual-licensed under
either the terms of the Eclipse Public License v1.0 as published by
the Eclipse Foundation
  or (per the licensee's choosing)
under the terms of the GNU Lesser General Public License version 2.1
as published by the Free Software Foundation.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core.recovery;

import java.io.IOException;
import java.io.OutputStream;

import ch.qos.logback.core.Context;
import ch.qos.logback.core.status.ErrorStatus;
import ch.qos.logback.core.status.InfoStatus;
import ch.qos.logback.core.status.Status;
import ch.qos.logback.core.status.StatusManager;

abstract public class ResilientOutputStreamBase extends OutputStream {

    final static int STATUS_COUNT_LIMIT = 2 * 4;

    private int noContextWarning = 0;
    private int statusCount = 0;

    private Context context;
    private RecoveryCoordinator recoveryCoordinator;

    protected OutputStream os;
    protected boolean presumedClean = true;

    private boolean isPresumedInError() {
        // existence of recoveryCoordinator indicates failed state
        return (recoveryCoordinator != null && !presumedClean);
    }

    public void write(byte b[], int off, int len) {
        if (isPresumedInError()) {
            if (!recoveryCoordinator.isTooSoon()) {
                attemptRecovery();
            }
            return; // return regardless of the success of the recovery attempt
        }

        try {
            os.write(b, off, len);
            postSuccessfulWrite();
        } catch (IOException e) {
            postIOFailure(e);
        }
    }

    @Override
    public void write(int b) {
        if (isPresumedInError()) {
            if (!recoveryCoordinator.isTooSoon()) {
                attemptRecovery();
            }
            return; // return regardless of the success of the recovery attempt
        }
        try {
            os.write(b);
            postSuccessfulWrite();
        } catch (IOException e) {
            postIOFailure(e);
        }
    }

    @Override
    public void flush() {
        if (os != null) {
            try {
                os.flush();
                postSuccessfulWrite();
            } catch (IOException e) {
                postIOFailure(e);
            }
        }
    }

    abstract String getDescription();

    abstract OutputStream openNewOutputStream() throws IOException;

    private void postSuccessfulWrite() {
        if (recoveryCoordinator != null) {
            recoveryCoordinator = null;
            statusCount = 0;
            addStatus(new InfoStatus("Recovered from IO failure on " + getDescription(), this));
        }
    }

    public void postIOFailure(IOException e) {
        addStatusIfCountNotOverLimit(new ErrorStatus("IO failure while writing to " + getDescription(), this, e));
        presumedClean = false;
        if (recoveryCoordinator == null) {
            recoveryCoordinator = new RecoveryCoordinator();
        }
    }

    @Override
    public void close() throws IOException {
        if (os != null) {
            os.close();
        }
    }

    void attemptRecovery() {
        try {
            close();
        } catch (IOException e) {
        }

        addStatusIfCountNotOverLimit(new InfoStatus("Attempting to recover from IO failure on " + getDescription(), this));

        // subsequent writes must always be in append mode
        try {
            os = openNewOutputStream();
            presumedClean = true;
        } catch (IOException e) {
            addStatusIfCountNotOverLimit(new ErrorStatus("Failed to open " + getDescription(), this, e));
        }
    }

    void addStatusIfCountNotOverLimit(Status s) {
        ++statusCount;
        if (statusCount < STATUS_COUNT_LIMIT) {
            addStatus(s);
        }

        if (statusCount == STATUS_COUNT_LIMIT) {
            addStatus(s);
            addStatus(new InfoStatus("Will supress future messages regarding " + getDescription(), this));
        }
    }

    public void addStatus(Status status) {
        if (context == null) {
            if (noContextWarning++ == 0) {
                System.out.println("LOGBACK: No context given for " + this);
            }
            return;
        }
        StatusManager sm = context.getStatusManager();
        if (sm != null) {
            sm.add(status);
        }
    }

    public Context getContext() {
        return context;
    }

    public void setContext(Context context) {
        this.context = context;
    }
}