Changes to HTTPMetricHandler to fix Issue #732

simpleclient_httpserver/src/main/java/io/prometheus/client/exporter/HTTPServer.java

@@ -116,7 +116,9 @@ public void handle(HttpExchange t) throws IOException {
                 }
             } else {
                 long contentLength = response.size();
-                t.getResponseHeaders().set("Content-Length", String.valueOf(contentLength));
+                if (contentLength > 0) {
+                    t.getResponseHeaders().set("Content-Length", String.valueOf(contentLength));
+                }
                 if (t.getRequestMethod().equals("HEAD")) {
                     contentLength = -1;
                 }

simpleclient_httpserver/src/test/java/io/prometheus/client/exporter/HttpRequest.java

@@ -0,0 +1,244 @@
+package io.prometheus.client.exporter;
+
+import javax.net.ssl.HostnameVerifier;
+import javax.net.ssl.HttpsURLConnection;
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.TrustManager;
+import javax.xml.bind.DatatypeConverter;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.net.URLConnection;
+import java.security.GeneralSecurityException;
+import java.security.KeyManagementException;
+import java.security.NoSuchAlgorithmException;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Scanner;
+import java.util.Set;
+
+/**
+ * Class to perform HTTP testing
+ */
+public class HttpRequest {
+
+    enum METHOD { GET, HEAD }
+
+    private final Configuration configuration;
+
+    /**
+     * Constructor
+     *
+     * @param configuration configuration
+     */
+    private HttpRequest(Configuration configuration) {
+        this.configuration = configuration;
+    }
+
+    /**
+     * Method to execute an HTTP request
+     *
+     * @return HttpResponse
+     * @throws IOException
+     */
+    public HttpResponse execute() throws IOException {
+        if (configuration.url.toLowerCase().startsWith("https://") && (configuration.trustManagers != null)) {
+            try {
+                SSLContext sslContext = SSLContext.getInstance("SSL");
+                sslContext.init(null, configuration.trustManagers, new java.security.SecureRandom());
+                HttpsURLConnection.setDefaultSSLSocketFactory(sslContext.getSocketFactory());
+            } catch (GeneralSecurityException e) {
+                throw new IOException(e);
+            }
+
+            if (configuration.hostnameVerifier != null) {
+                HttpsURLConnection.setDefaultHostnameVerifier(configuration.hostnameVerifier);
+            }
+        }
+
+        URLConnection urlConnection = new URL(configuration.url).openConnection();
+        ((HttpURLConnection) urlConnection).setRequestMethod(configuration.method.toString());
+
+        Set<Map.Entry<String, List<String>>> entries = configuration.headers.entrySet();
+        for (Map.Entry<String, List<String>> entry : entries) {
+            for (String value : entry.getValue()) {
+                urlConnection.addRequestProperty(entry.getKey(), value);
+            }
+        }
+
+        urlConnection.setUseCaches(false);
+        urlConnection.setDoInput(true);
+        urlConnection.setDoOutput(true);
+        urlConnection.connect();
+
+        Scanner scanner = new Scanner(urlConnection.getInputStream(), "UTF-8").useDelimiter("\\A");
+
+        return new HttpResponse(
+                ((HttpURLConnection) urlConnection).getResponseCode(),
+                urlConnection.getHeaderFields(),
+                        urlConnection.getContentLength(), scanner.hasNext() ? scanner.next() : "");
+    }
+
+    /**
+     * Class to build an HttpRequest
+     */
+    static class Builder {
+
+        private final Configuration configuration;
+
+        /**
+         * Constructor
+         */
+        public Builder() {
+            configuration = new Configuration();
+        }
+
+        /**
+         * Method to set the HTTP request method
+         *
+         * @param method
+         * @return Builder
+         */
+        public Builder withMethod(METHOD method) {
+            configuration.method = method;
+            return this;
+        }
+
+        /**
+         * Method to set the HTTP request URL
+         *
+         * @param url
+         * @return Builder
+         */
+        public Builder withURL(String url) {
+            configuration.url = url;
+            return this;
+        }
+
+        /**
+         * Method to add an HTTP request header
+         *
+         * @param name
+         * @param value
+         * @return Builder
+         */
+        public Builder withHeader(String name, String value) {
+            configuration.addHeader(name, value);
+            return this;
+        }
+
+        /**
+         * Method to set the HTTP request "Authorization" header
+         *
+         * @param username
+         * @param password
+         * @return Builder
+         */
+        public Builder withAuthorization(String username, String password) {
+            configuration.setHeader("Authorization", encodeCredentials(username, password));
+            return this;
+        }
+
+        /**
+         * Method to set the HTTP request trust managers when using an SSL URL
+         *
+         * @param trustManagers
+         * @return Builder
+         */
+        public Builder withTrustManagers(TrustManager[] trustManagers) {
+            configuration.trustManagers = trustManagers;
+            return this;
+        }
+
+        /**
+         * Method to set the HTTP request hostname verifier when using an SSL URL
+         *
+         * @param hostnameVerifier
+         * @return Builder
+         */
+        public Builder withHostnameVerifier(HostnameVerifier hostnameVerifier) {
+            configuration.hostnameVerifier = hostnameVerifier;
+            return this;
+        }
+
+        /**
+         * Method to build the HttpRequest
+         *
+         * @return HttpRequest
+         */
+        public HttpRequest build() {
+            return new HttpRequest(configuration);
+        }
+    }
+
+    /**
+     * Class used for Builder configuration
+     */
+    private static class Configuration {
+
+        public METHOD method;
+        public String url;
+        public Map<String, List<String>> headers;
+        public TrustManager[] trustManagers;
+        public HostnameVerifier hostnameVerifier;
+
+        /**
+         * Constructor
+         */
+        Configuration() {
+            method = METHOD.GET;
+            headers = new HashMap<String, List<String>>();
+        }
+
+        /**
+         * Method to add (append) an HTTP request header
+         *
+         * @param name
+         * @param value
+         * @return Configuration
+         */
+        void addHeader(String name, String value) {
+            name = name.toLowerCase();
+            List<String> values = headers.get(name);
+            if (values == null) {
+                values = new LinkedList<String>();
+                headers.put(name, values);
+            }
+
+            values.add(value);
+        }
+
+        /**
+         * Method to set (overwrite) an HTTP request header, removing all previous header values
+         *
+         * @param name
+         * @param value
+         * @return Configuration
+         */
+        void setHeader(String name, String value) {
+            List<String> values = new LinkedList<String>();
+            values.add(value);
+            headers.put(name, values);
+        }
+    }
+
+    /**
+     * Method to encode "Authorization" credentials
+     *
+     * @param username
+     * @param password
+     * @return String
+     */
+    private final static String encodeCredentials(String username, String password) {
+        // Per RFC4648 table 2. We support Java 6, and java.util.Base64 was only added in Java 8,
+        try {
+            byte[] credentialsBytes = (username + ":" + password).getBytes("UTF-8");
+            return "Basic " + DatatypeConverter.printBase64Binary(credentialsBytes);
+        } catch (UnsupportedEncodingException e) {
+            throw new IllegalArgumentException(e);
+        }
+    }
+}

simpleclient_httpserver/src/test/java/io/prometheus/client/exporter/HttpResponse.java

@@ -0,0 +1,109 @@
+package io.prometheus.client.exporter;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Class to perform HTTP testing
+ */
+class HttpResponse {
+
+    private int responseCode;
+    private Map<String, List<String>> headers;
+    private long contentLength = -1;
+    private String body;
+
+    /**
+     * Constructor
+     *
+     * @param responseCode
+     * @param headers
+     * @param contentLength
+     * @param body
+     */
+    HttpResponse(int responseCode, Map<String, List<String>> headers, long contentLength, String body) throws IOException {
+        this.responseCode = responseCode;
+        this.body = body;
+        this.contentLength = contentLength;
+        this.headers = new HashMap<String, List<String>>();
+
+        Set<Map.Entry<String, List<String>>> headerSet = headers.entrySet();
+        for (String header : headers.keySet()) {
+            if (header != null) {
+                List<String> values = headers.get(header);
+                this.headers.put(header.toLowerCase(), values);
+            }
+        }
+
+        if (getHeader("content-length") != null && getHeader("transfer-encoding") != null) {
+            throw new IOException("Invalid HTTP response, should only contain Connect-Length or Transfer-Encoding");
+        }
+    }
+
+    /**
+     * Method to get the HTTP response code
+     *
+     * @return int
+     */
+    public int getResponseCode() {
+        return this.responseCode;
+    }
+
+    /**
+     * Method to get a list of HTTP response headers values
+     *
+     * @param name
+     * @return List<String>
+     */
+    public List<String> getHeaderList(String name) {
+        return headers.get(name.toLowerCase());
+    }
+
+    /**
+     * Method to get the first HTTP response header value
+     *
+     * @param name
+     * @return String
+     */
+    public String getHeader(String name) {
+        String value = null;
+
+        List<String> valueList = getHeaderList(name);
+        if (valueList != null && (valueList.size() >= 0)) {
+            value = valueList.get(0);
+        }
+
+        return value;
+    }
+
+    /**
+     * Method to get the first HTTP response header value as a Long.
+     * Returns null of the header doesn't exist
+     *
+     * @param name
+     * @return Long
+     */
+    public Long getHeaderAsLong(String name) {
+        String value = getHeader(name);
+        if (value != null) {
+            try {
+                return Long.valueOf(value);
+            } catch (Exception e) {
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Method to get the HTTP response body
+     *
+     * @return String
+     */
+    public String getBody() {
+        return body;
+    }
+}