RestEasy client: Invalid use of BasicClientConnManager: connection still allocated - resteasy

Question

I am using RestEasy client to retrieve a list of entities from web server. This is my code:
#ApplicationScoped
public class RestHttpClient {
private ResteasyClient client;
#Inject
private ObjectMapper mapper;
#PostConstruct
public void initialize() {
HttpParams params = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(params, 5000);
HttpConnectionParams.setSoTimeout(params, 5000);
HttpClient httpClient = new DefaultHttpClient(params);
this.client = new ResteasyClientBuilder().httpEngine(new ApacheHttpClient4Engine(httpClient)).build();
}
public <E> List<E> getList(final Class<E> resultClass, final String path,
MultivaluedMap<String, Object> queryParams) {
ResteasyWebTarget target = this.client.target(path);
Response response = null;
try {
response = target.queryParams(queryParams).request().get();
String jsonString = response.readEntity(String.class);
TypeFactory typeFactory = TypeFactory.defaultInstance();
List<E> list = this.mapper.readValue(
jsonString, typeFactory.constructCollectionType(ArrayList.class, resultClass));
return list;
} catch (Exception e) {
// Handle exception
} finally {
if (response != null)
response.close();
}
return null;
}
}
It works fine, but... if I call getList() method multiple times in quick succession, sometimes I get the error "Invalid use of BasicClientConnManager: connection still allocated". I can make the same sequence of calls over and over again, and it works at least 90% of the time, so it appears to be a race condition. I am closing the Response object in finally block, which should be enough to release all resources, but apparently it isn't. What else do I have to do to make sure the connection is released? I have found some answers on the net, but they are either too old or not RestEasy-specific. I am using resteasy-client 3.0.4.Final.

Answer 1

I guess you only have one instance of your class RestHttpClient, and all threads/requests are using the same object.
The default ResteasyClientBuilder does not use a connection pool. Which means you can have only one parallel connection at a time. A request needs to be returned before you can use the ResteasyClient a second time (error message "connection still allocated"). You can avoid that by increasing the connection pool size:
ResteasyClientBuilder clientBuilder = new ResteasyClientBuilder();
clientBuilder = clientBuilder.connectionPoolSize( 20 );
ResteasyWebTarget target = clientBuilder.build().target( "http://your.host" );
I am using the following RestClientFactory to set up a new client. It gives you a debug output of the raw response, specifies the keystore (needed for client ssl certificates), a connection pool and the option for the use of a proxy.
public class RestClientFactory {
public static class Options {
private final String baseUri;
private final String proxyHostname;
private final String proxyPort;
private final String keystore;
private final String keystorePassword;
private final String connectionPoolSize;
private final String connectionTTL;
public Options(String baseUri, String proxyHostname, String proxyPort) {
this.baseUri = baseUri;
this.proxyHostname = proxyHostname;
this.proxyPort = proxyPort;
this.connectionPoolSize = "100";
this.connectionTTL = "500";
this.keystore = System.getProperty( "javax.net.ssl.keyStore" );
this.keystorePassword = System.getProperty( "javax.net.ssl.keyStorePassword" );
}
public Options(String baseUri, String proxyHostname, String proxyPort, String keystore, String keystorePassword, String connectionPoolSize, String connectionTTL) {
this.baseUri = baseUri;
this.proxyHostname = proxyHostname;
this.proxyPort = proxyPort;
this.connectionPoolSize = connectionPoolSize;
this.connectionTTL = connectionTTL;
this.keystore = keystore;
this.keystorePassword = keystorePassword;
}
}
private static Logger log = LoggerFactory.getLogger( RestClientFactory.class );
public static <T> T createClient(Options options, Class<T> proxyInterface) throws Exception {
log.info( "creating ClientBuilder using options {}", ReflectionToStringBuilder.toString( options ) );
ResteasyClientBuilder clientBuilder = new ResteasyClientBuilder();
ResteasyProviderFactory providerFactory = new ResteasyProviderFactory();
RegisterBuiltin.register( providerFactory );
providerFactory.getClientReaderInterceptorRegistry().registerSingleton( new ReaderInterceptor() {
#Override
public Object aroundReadFrom(ReaderInterceptorContext context) throws IOException, WebApplicationException {
if (log.isDebugEnabled()) {
InputStream is = context.getInputStream();
String responseBody = IOUtils.toString( is );
log.debug( "received response:\n{}\n\n", responseBody );
context.setInputStream( new ByteArrayInputStream( responseBody.getBytes() ) );
}
return context.proceed();
}
} );
clientBuilder.providerFactory( providerFactory );
if (StringUtils.isNotBlank( options.proxyHostname ) && StringUtils.isNotBlank( options.proxyPort )) {
clientBuilder = clientBuilder.defaultProxy( options.proxyHostname, Integer.parseInt( options.proxyPort ) );
}
// why the fuck do you have to specify the keystore with RestEasy?
// not setting the keystore will result in not using the global one
if ((StringUtils.isNotBlank( options.keystore )) && (StringUtils.isNotBlank( options.keystorePassword ))) {
KeyStore ks;
ks = KeyStore.getInstance( KeyStore.getDefaultType() );
FileInputStream fis = new FileInputStream( options.keystore );
ks.load( fis, options.keystorePassword.toCharArray() );
fis.close();
clientBuilder = clientBuilder.keyStore( ks, options.keystorePassword );
// Not catching these exceptions on purpose
}
if (StringUtils.isNotBlank( options.connectionPoolSize )) {
clientBuilder = clientBuilder.connectionPoolSize( Integer.parseInt( options.connectionPoolSize ) );
}
if (StringUtils.isNotBlank( options.connectionTTL )) {
clientBuilder = clientBuilder.connectionTTL( Long.parseLong( options.connectionTTL ), TimeUnit.MILLISECONDS );
}
ResteasyWebTarget target = clientBuilder.build().target( options.baseUri );
return target.proxy( proxyInterface );
}
}
An example client interface:
public interface SimpleClient
{
#GET
#Path("basic")
#Produces("text/plain")
String getBasic();
}
Create a client:
SimpleClient client = RestClientFactory.createClient(
new RestClientFactory.Options(
"https://your.service.host",
"proxyhost",
"8080",
"keystore.jks",
"changeit",
"20",
"500"
)
,SimpleClient.class
);
See also:
http://docs.jboss.org/resteasy/docs/3.0-beta-3/userguide/html/RESTEasy_Client_Framework.html#d4e2049