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sdk/java: accept multiple URLs in Client
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Allow the Java SDK Client to be configured with multiple cored or
signerd URLs for high availability in the absence of a load balancer.

Closes #486
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@jbowens @iampogo
jbowens authored and iampogo committed Feb 8, 2017
1 parent a9924bf commit 66f8518
Showing 1 changed file with 100 additions and 39 deletions.
139 changes: 100 additions & 39 deletions sdk/java/src/main/java/com/chain/http/Client.java
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Expand Up @@ -7,9 +7,13 @@
import java.io.InputStreamReader;
import java.lang.reflect.Type;
import java.net.*;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.List;
import java.util.Objects;

import com.google.gson.Gson;

Expand All @@ -31,7 +35,8 @@
*/
public class Client {

private URL url;
private AtomicInteger urlIndex;
private List<URL> urls;
private String accessToken;
private OkHttpClient httpClient;
private static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");
Expand All @@ -51,7 +56,17 @@ private static class BuildProperties {
}

public Client(Builder builder) {
this.url = builder.url;
List<URL> urls = new ArrayList<URL>(builder.urls);
if (urls.isEmpty()) {
try {
urls.add(new URL("http://localhost:1999"));
} catch (MalformedURLException e) {
throw new RuntimeException("invalid default development URL", e);
}
}

this.urlIndex = new AtomicInteger(0);
this.urls = urls;
this.accessToken = builder.accessToken;
this.httpClient = buildHttpClient(builder);
}
Expand Down Expand Up @@ -191,11 +206,19 @@ public T create(Response response, Gson deserializer) throws ChainException, IOE
}

/**
* Returns the base url stored in the client.
* @return the client's base url
* Returns the preferred base URL stored in the client.
* @return the client's base URL
*/
public URL url() {
return this.url;
return this.urls.get(0);
}

/**
* Returns the list of base URLs used by the client.
* @return the client's base URLs
*/
public List<URL> urls() {
return new ArrayList<>(this.urls);
}

/**
Expand Down Expand Up @@ -289,22 +312,31 @@ private <T> T post(String path, Object body, ResponseCreator<T> respCreator)
RequestBody requestBody = RequestBody.create(this.JSON, serializer.toJson(body));
Request req;

try {
ChainException exception = null;
for (int attempt = 1; attempt - 1 <= MAX_RETRIES; attempt++) {

int idx = this.urlIndex.get();
URL endpointURL;
try {
URI u = new URI(this.urls.get(idx).toString() + "/" + path);
u = u.normalize();
endpointURL = new URL(u.toString());
} catch (MalformedURLException ex) {
throw new BadURLException(ex.getMessage());
} catch (URISyntaxException ex) {
throw new BadURLException(ex.getMessage());
}

Request.Builder builder =
new Request.Builder()
.header("User-Agent", "chain-sdk-java/" + version)
.url(this.createEndpoint(path))
.url(endpointURL)
.method("POST", requestBody);
if (hasAccessToken()) {
builder = builder.header("Authorization", buildCredentials());
}
req = builder.build();
} catch (MalformedURLException ex) {
throw new BadURLException(ex.getMessage());
}

ChainException exception = null;
for (int attempt = 1; attempt - 1 <= MAX_RETRIES; attempt++) {
// Wait between retrys. The first attempt will not wait at all.
if (attempt > 1) {
int delayMillis = retryDelayMillis(attempt - 1);
Expand All @@ -318,14 +350,23 @@ private <T> T post(String path, Object body, ResponseCreator<T> respCreator)
Response resp = this.checkError(this.httpClient.newCall(req).execute());
return respCreator.create(resp, serializer);
} catch (IOException ex) {
// This URL's process might be unhealthy; move to the next.
this.nextURL(idx);

// The OkHttp library already performs retries for most
// I/O-related errors. We can add retries here too if this
// becomes a problem.
throw new HTTPException(ex.getMessage());
} catch (ConnectivityException ex) {
// This URL's process might be unhealthy; move to the next.
this.nextURL(idx);

// ConnectivityExceptions are always retriable.
exception = ex;
} catch (APIException ex) {
// This URL's process might be unhealthy; move to the next.
this.nextURL(idx);

// Check if this error is retriable (either it's a status code that's
// always retriable or the error is explicitly marked as temporary.
if (!isRetriableStatusCode(ex.statusCode) && !ex.temporary) {
Expand Down Expand Up @@ -414,14 +455,15 @@ private Response checkError(Response response) throws ChainException {
return response;
}

private URL createEndpoint(String path) throws MalformedURLException {
try {
URI u = new URI(this.url.toString() + "/" + path);
u = u.normalize();
return new URL(u.toString());
} catch (URISyntaxException e) {
throw new MalformedURLException();
private void nextURL(int failedIndex) {
if (this.urls.size() == 1) {
return; // No point contending on the CAS if there's only one URL.
}

// A request to the url at failedIndex just failed. Move to the next
// URL in the list.
int nextIndex = (failedIndex + 1) % this.urls.size();
this.urlIndex.compareAndSet(failedIndex, nextIndex);
}

private String buildCredentials() {
Expand All @@ -439,21 +481,17 @@ private String buildCredentials() {
return Credentials.basic(user, pass);
}

private String identifier() {
if (this.hasAccessToken()) {
return String.format(
"%s://%s@%s", this.url.getProtocol(), this.accessToken, this.url.getAuthority());
}
return String.format("%s://%s", this.url.getProtocol(), this.url.getAuthority());
}

/**
* Overrides {@link Object#hashCode()}
* @return the hash code
*/
@Override
public int hashCode() {
return identifier().hashCode();
int code = this.urls.hashCode();
if (this.hasAccessToken()) {
code = code * 31 + this.accessToken.hashCode();
}
return code;
}

/**
Expand All @@ -467,14 +505,17 @@ public boolean equals(Object o) {
if (!(o instanceof Client)) return false;

Client other = (Client) o;
return this.identifier().equals(other.identifier());
if (!this.urls.equals(other.urls)) {
return false;
}
return Objects.equals(this.accessToken, other.accessToken);
}

/**
* A builder class for creating client objects
*/
public static class Builder {
private URL url;
private List<URL> urls;
private String accessToken;
private CertificatePinner cp;
private long connectTimeout;
Expand All @@ -487,40 +528,60 @@ public static class Builder {
private ConnectionPool pool;

public Builder() {
this.urls = new ArrayList<URL>();
this.setDefaults();
}

private void setDefaults() {
try {
this.url = new URL("http://localhost:1999");
} catch (MalformedURLException e) {
throw new RuntimeException("invalid default development URL", e);
}
this.setReadTimeout(30, TimeUnit.SECONDS);
this.setWriteTimeout(30, TimeUnit.SECONDS);
this.setConnectTimeout(30, TimeUnit.SECONDS);
this.setConnectionPool(50, 2, TimeUnit.MINUTES);
}

/**
* Sets the URL for the client
* Adds a base URL for the client to use.
* @param url the URL of the Chain Core or HSM.
*/
public Builder addURL(String url) throws BadURLException {
try {
this.urls.add(new URL(url));
} catch (MalformedURLException e) {
throw new BadURLException(e.getMessage());
}
return this;
}

/**
* Adds a base URL for the client to use.
* @param url the URL of the Chain Core or HSM.
*/
public Builder addURL(URL url) {
this.urls.add(url);
return this;
}

/**
* Sets the URL for the client. It replaces all existing Chain Core
* URLs with the provided URL.
* @param url the URL of the Chain Core or HSM
*/
public Builder setURL(String url) throws BadURLException {
try {
this.url = new URL(url);
this.urls = new ArrayList<URL>(Arrays.asList(new URL(url)));
} catch (MalformedURLException e) {
throw new BadURLException(e.getMessage());
}
return this;
}

/**
* Sets the URL for the client
* Sets the URL for the client. It replaces all existing Chain Core
* URLs with the provided URL.
* @param url the URL of the Chain Core or HSM
*/
public Builder setURL(URL url) {
this.url = url;
this.urls = new ArrayList<URL>(Arrays.asList(url));
return this;
}

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