zookeeper 3.4.6启动流程粗略梳理
/** * Handles read/write IO on connection.*/
void doIO(SelectionKey k) throws InterruptedException {
try {
if (isSocketOpen() == false) {
LOG.warn("trying to do i/o on a null socket for session:0x"
+ Long.toHexString(sessionId));
return;
}
if (k.isReadable()) {
int rc = sock.read(incomingBuffer);
if (rc < 0) {
throw new EndOfStreamException(
"Unable to read additional data from client sessionid 0x"
+ Long.toHexString(sessionId)
+ ", likely client has closed socket");
}
if (incomingBuffer.remaining() == 0) {
boolean isPayload;
if (incomingBuffer == lenBuffer) { // start of next request
incomingBuffer.flip();
isPayload = readLength(k);
incomingBuffer.clear();
} else {
// continuation
isPayload = true;
}
if (isPayload) { // not the case for 4letterword
readPayload();
}
else {
// four letter words take care
// need not do anything else
return;
}
}
}
if (k.isWritable()) {
// ZooLog.logTraceMessage(LOG,
// ZooLog.CLIENT_DATA_PACKET_TRACE_MASK
// "outgoingBuffers.size() = " +
// outgoingBuffers.size());
if (outgoingBuffers.size() > 0) {
// ZooLog.logTraceMessage(LOG,
// ZooLog.CLIENT_DATA_PACKET_TRACE_MASK,
// "sk " + k + " is valid: " +
// k.isValid());
/*
* This is going to reset the buffer position to 0 and the
* limit to the> * with data from the non-direct buffers that we need to
* send.
*/
ByteBuffer directBuffer = factory.directBuffer;
directBuffer.clear();
for (ByteBuffer b : outgoingBuffers) {
if (directBuffer.remaining() < b.remaining()) {
/*
* When we call put later, if the directBuffer is to
* small to hold everything, nothing will be copied,
* so we've got to slice the buffer if it's too big.
*/
b = (ByteBuffer) b.slice().limit(
directBuffer.remaining());
}
/*
* put() is going to modify the positions of both
* buffers, put we don't want to change the position of
* the source buffers (we'll do that after the send, if
* needed), so we save and reset the position after the
* copy
*/
int p = b.position();
directBuffer.put(b);
b.position(p);
if (directBuffer.remaining() == 0) {
break;
}
}
/*
* Do the flip: limit becomes position, position gets set to
* 0. This sets us up for the write.
*/
directBuffer.flip();
int sent = sock.write(directBuffer);
ByteBuffer bb;
// Remove the buffers that we have sent
while (outgoingBuffers.size() > 0) {
bb = outgoingBuffers.peek();
if (bb == ServerCnxnFactory.closeConn) {
throw new CloseRequestException("close requested");
}
int left = bb.remaining() - sent;
if (left > 0) {
/*
* We only partially sent this buffer, so we update
* the position and exit the loop.
*/
bb.position(bb.position() + sent);
break;
}
packetSent();
/* We've sent the whole buffer, so drop the buffer */
sent -= bb.remaining();
outgoingBuffers.remove();
}
// ZooLog.logTraceMessage(LOG,
// ZooLog.CLIENT_DATA_PACKET_TRACE_MASK, "after send,
// outgoingBuffers.size() = " + outgoingBuffers.size());
}
synchronized(this.factory){
if (outgoingBuffers.size() == 0) {
if (!initialized
&& (sk.interestOps() & SelectionKey.OP_READ) == 0) {
throw new CloseRequestException("responded to info probe");
}
sk.interestOps(sk.interestOps()
& (~SelectionKey.OP_WRITE));
} else {
sk.interestOps(sk.interestOps()
| SelectionKey.OP_WRITE);
}
}
}
} catch (CancelledKeyException e) {
LOG.warn("Exception causing close of session 0x"
+ Long.toHexString(sessionId)
+ " due to " + e);
if (LOG.isDebugEnabled()) {
LOG.debug("CancelledKeyException stack trace", e);
}
close();
} catch (CloseRequestException e) {
// expecting close to log session closure
close();
} catch (EndOfStreamException e) {
LOG.warn("caught end of stream exception",e); // tell user why
// expecting close to log session closure
close();
} catch (IOException e) {
LOG.warn("Exception causing close of session 0x"
+ Long.toHexString(sessionId)
+ " due to " + e);
if (LOG.isDebugEnabled()) {
LOG.debug("IOException stack trace", e);
}
close();
}
}
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