THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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In order to create a BookKeeper client you have to setup a ClientConfiguration object.
The most important parameter is the ZooKeeper connection string, which is needed to access to the BookKeeper ensemble.
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ClientConfiguration config = new ClientConfiguration();
config.setZkServers("localhost:1281");
try (BookKeeper bookKeeper = BookKeeper.forConfig(config).build();) {
// ...
} |
If you already have a ZooKeeper handle and you want to share it you have to pass it the Builder
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ZooKeeper zookeeper = ....; ClientConfiguration config = new ClientConfiguration(); config.setZkServers("localhost:1281"); try (BookKeeper bookKeeper = BookKeeper .forConfig(config) .setZookeeper(zookeeper) .build();) { // ... } |
Beware that ClientConfiguration will be automatically filled with System.getProperties()
Synch vs Asynch
(explanation of the existance of both a synch API and a asynch API)
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BookKeeper API methods provide access to BookKeeper features, internally all is asynchronous and in general the asynch API will give you more control about whats going on and result in better performances.
For instance
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try (LedgerHandle handle = bookkeeper.createLedger(1, 1, 1, BookKeeper.DigestType.CRC32, "test".getBytes())) {
byte[] data = "test".getBytes();
final CountDownLatch la = new CountDownLatch(SIZE);
for (int i = 0; i < SIZE; i++) {
handle.asyncAddEntry(data, new AsyncCallback.AddCallback() {
@Override
public void addComplete(int rc, LedgerHandle lh, long l, Object o) {
if (rc != BKException.Code.OK) {
System.err.println("Error: "+BKException.getMessage(rc));
}
assertEquals("callback_param",o);
la.countDown();
}
}, "callback_param");
}
la.await();
} |
A similar code using the synch API is:
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try (LedgerHandle handle = bookkeeper.createLedger(1, 1, 1, BookKeeper.DigestType.CRC32, "test".getBytes())) {
byte[] data = "test".getBytes();
for (int i = 0; i < SIZE; i++) {
handle.addEntry(data);
}
} |
The async API will be really more efficient from the standpoint of speed but you have to deal with callbacks, remember that:
- callbacks are called in a different thread
- exception will not be thrown in the main (callee) thread but you have to switch over the 'rc' (return code) parameter, using the BKException.Code class or BKException.create(rc) method
- you have no direct control on the pool of threads which executes the callbacks
Writing to a Ledger
Reading from a Ledger
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