Adding upstream version 2.4.57.upstream/2.4.57upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1351 insertions, 0 deletions

diff --git a/modules/proxy/mod_proxy_hcheck.c b/modules/proxy/mod_proxy_hcheck.c
new file mode 100644
index 0000000..d618b4d
--- /dev/null
+++ b/modules/proxy/mod_proxy_hcheck.c
@@ -0,0 +1,1351 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "mod_proxy.h"
+#include "mod_watchdog.h"
+#include "ap_slotmem.h"
+#include "ap_expr.h"
+#if APR_HAS_THREADS
+#include "apr_thread_pool.h"
+#endif
+#include "http_ssl.h"
+
+module AP_MODULE_DECLARE_DATA proxy_hcheck_module;
+
+#define HCHECK_WATHCHDOG_NAME ("_proxy_hcheck_")
+#define HC_THREADPOOL_SIZE (16)
+
+/* Why? So we can easily set/clear HC_USE_THREADS during dev testing */
+#if APR_HAS_THREADS
+#ifndef HC_USE_THREADS
+#define HC_USE_THREADS 1
+#endif
+#else
+#define HC_USE_THREADS 0
+#endif
+
+typedef struct {
+    char *name;
+    hcmethod_t method;
+    int passes;
+    int fails;
+    apr_interval_time_t interval;
+    char *hurl;
+    char *hcexpr;
+} hc_template_t;
+
+typedef struct {
+    char *expr;
+    ap_expr_info_t *pexpr;       /* parsed expression */
+} hc_condition_t;
+
+typedef struct {
+    apr_pool_t *p;
+    apr_array_header_t *templates;
+    apr_table_t *conditions;
+    apr_hash_t *hcworkers;
+    server_rec *s;
+} sctx_t;
+
+/* Used in the HC worker via the context field */
+typedef struct {
+    const char *path;   /* The path of the original worker URL */
+    const char *method; /* Method string for the HTTP/AJP request */
+    const char *req;    /* pre-formatted HTTP/AJP request */
+    proxy_worker *w;    /* Pointer to the actual worker */
+    const char *protocol; /* HTTP 1.0 or 1.1? */
+} wctx_t;
+
+typedef struct {
+    apr_pool_t *ptemp;
+    sctx_t *ctx;
+    proxy_balancer *balancer;
+    proxy_worker *worker;
+    proxy_worker *hc;
+    apr_time_t *now;
+} baton_t;
+
+static APR_OPTIONAL_FN_TYPE(ajp_handle_cping_cpong) *ajp_handle_cping_cpong = NULL;
+
+static void *hc_create_config(apr_pool_t *p, server_rec *s)
+{
+    sctx_t *ctx = apr_pcalloc(p, sizeof(sctx_t));
+    ctx->s = s;
+    apr_pool_create(&ctx->p, p);
+    apr_pool_tag(ctx->p, "proxy_hcheck");
+    ctx->templates = apr_array_make(p, 10, sizeof(hc_template_t));
+    ctx->conditions = apr_table_make(p, 10);
+    ctx->hcworkers = apr_hash_make(p);
+    return ctx;
+}
+
+static ap_watchdog_t *watchdog;
+#if HC_USE_THREADS
+static apr_thread_pool_t *hctp;
+static int tpsize;
+#endif
+
+/*
+ * This serves double duty by not only validating (and creating)
+ * the health-check template, but also ties into set_worker_param()
+ * which does the actual setting of worker params in shm.
+ */
+static const char *set_worker_hc_param(apr_pool_t *p,
+                                    server_rec *s,
+                                    proxy_worker *worker,
+                                    const char *key,
+                                    const char *val,
+                                    void *v)
+{
+    int ival;
+    hc_template_t *temp;
+    sctx_t *ctx = (sctx_t *) ap_get_module_config(s->module_config,
+                                                  &proxy_hcheck_module);
+    if (!worker && !v) {
+        return "Bad call to set_worker_hc_param()";
+    }
+    if (!ctx) {
+        ctx = hc_create_config(p, s);
+        ap_set_module_config(s->module_config, &proxy_hcheck_module, ctx);
+    }
+    temp = (hc_template_t *)v;
+    if (!strcasecmp(key, "hctemplate")) {
+        hc_template_t *template;
+        template = (hc_template_t *)ctx->templates->elts;
+        for (ival = 0; ival < ctx->templates->nelts; ival++, template++) {
+            if (!ap_cstr_casecmp(template->name, val)) {
+                if (worker) {
+                    worker->s->method = template->method;
+                    worker->s->interval = template->interval;
+                    worker->s->passes = template->passes;
+                    worker->s->fails = template->fails;
+                    PROXY_STRNCPY(worker->s->hcuri, template->hurl);
+                    PROXY_STRNCPY(worker->s->hcexpr, template->hcexpr);
+                } else {
+                    temp->method = template->method;
+                    temp->interval = template->interval;
+                    temp->passes = template->passes;
+                    temp->fails = template->fails;
+                    temp->hurl = apr_pstrdup(p, template->hurl);
+                    temp->hcexpr = apr_pstrdup(p, template->hcexpr);
+                }
+                return NULL;
+            }
+        }
+        return apr_psprintf(p, "Unknown ProxyHCTemplate name: %s", val);
+    }
+    else if (!strcasecmp(key, "hcmethod")) {
+        proxy_hcmethods_t *method = proxy_hcmethods;
+        for (; method->name; method++) {
+            if (!ap_cstr_casecmp(val, method->name)) {
+                if (!method->implemented) {
+                    return apr_psprintf(p, "Health check method %s not (yet) implemented",
+                                        val);
+                }
+                if (worker) {
+                    worker->s->method = method->method;
+                } else {
+                    temp->method = method->method;
+                }
+                return NULL;
+            }
+        }
+        return "Unknown method";
+    }
+    else if (!strcasecmp(key, "hcinterval")) {
+        apr_interval_time_t hci;
+        apr_status_t rv;
+        rv = ap_timeout_parameter_parse(val, &hci, "s");
+        if (rv != APR_SUCCESS)
+            return "Unparse-able hcinterval setting";
+        if (hci < AP_WD_TM_SLICE)
+            return apr_psprintf(p, "Interval must be a positive value greater than %"
+                                APR_TIME_T_FMT "ms", apr_time_as_msec(AP_WD_TM_SLICE));
+        if (worker) {
+            worker->s->interval = hci;
+        } else {
+            temp->interval = hci;
+        }
+    }
+    else if (!strcasecmp(key, "hcpasses")) {
+        ival = atoi(val);
+        if (ival < 0)
+            return "Passes must be a positive value";
+        if (worker) {
+            worker->s->passes = ival;
+        } else {
+            temp->passes = ival;
+        }
+    }
+    else if (!strcasecmp(key, "hcfails")) {
+        ival = atoi(val);
+        if (ival < 0)
+            return "Fails must be a positive value";
+        if (worker) {
+            worker->s->fails = ival;
+        } else {
+            temp->fails = ival;
+        }
+    }
+    else if (!strcasecmp(key, "hcuri")) {
+        if (strlen(val) >= sizeof(worker->s->hcuri))
+            return apr_psprintf(p, "Health check uri length must be < %d characters",
+                    (int)sizeof(worker->s->hcuri));
+        if (worker) {
+            PROXY_STRNCPY(worker->s->hcuri, val);
+        } else {
+            temp->hurl = apr_pstrdup(p, val);
+        }
+    }
+    else if (!strcasecmp(key, "hcexpr")) {
+        hc_condition_t *cond;
+        cond = (hc_condition_t *)apr_table_get(ctx->conditions, val);
+        if (!cond) {
+            return apr_psprintf(p, "Unknown health check condition expr: %s", val);
+        }
+        /* This check is wonky... a known expr can't be this big. Check anyway */
+        if (strlen(val) >= sizeof(worker->s->hcexpr))
+            return apr_psprintf(p, "Health check uri length must be < %d characters",
+                    (int)sizeof(worker->s->hcexpr));
+        if (worker) {
+            PROXY_STRNCPY(worker->s->hcexpr, val);
+        } else {
+            temp->hcexpr = apr_pstrdup(p, val);
+        }
+    }
+  else {
+        return "unknown Worker hcheck parameter";
+    }
+    return NULL;
+}
+
+static const char *set_hc_condition(cmd_parms *cmd, void *dummy, const char *arg)
+{
+    char *name = NULL;
+    char *expr;
+    sctx_t *ctx;
+    hc_condition_t *cond;
+
+    const char *err = ap_check_cmd_context(cmd, NOT_IN_HTACCESS);
+    if (err)
+        return err;
+    ctx = (sctx_t *) ap_get_module_config(cmd->server->module_config,
+                                          &proxy_hcheck_module);
+
+    name = ap_getword_conf(cmd->pool, &arg);
+    if (!*name) {
+        return apr_pstrcat(cmd->temp_pool, "Missing expression name for ",
+                           cmd->cmd->name, NULL);
+    }
+    if (strlen(name) > (PROXY_WORKER_MAX_SCHEME_SIZE - 1)) {
+        return apr_psprintf(cmd->temp_pool, "Expression name limited to %d characters",
+                           (PROXY_WORKER_MAX_SCHEME_SIZE - 1));
+    }
+    /* get expr. Allow fancy new {...} quoting style */
+    expr = ap_getword_conf2(cmd->temp_pool, &arg);
+    if (!*expr) {
+        return apr_pstrcat(cmd->temp_pool, "Missing expression for ",
+                           cmd->cmd->name, NULL);
+    }
+    cond = apr_palloc(cmd->pool, sizeof(hc_condition_t));
+    cond->pexpr = ap_expr_parse_cmd(cmd, expr, 0, &err, NULL);
+    if (err) {
+        return apr_psprintf(cmd->temp_pool, "Could not parse expression \"%s\": %s",
+                            expr, err);
+    }
+    cond->expr = apr_pstrdup(cmd->pool, expr);
+    apr_table_setn(ctx->conditions, name, (void *)cond);
+    expr = ap_getword_conf(cmd->temp_pool, &arg);
+    if (*expr) {
+        return "error: extra parameter(s)";
+    }
+    return NULL;
+}
+
+static const char *set_hc_template(cmd_parms *cmd, void *dummy, const char *arg)
+{
+    char *name = NULL;
+    char *word, *val;
+    hc_template_t *template;
+    sctx_t *ctx;
+
+    const char *err = ap_check_cmd_context(cmd, NOT_IN_HTACCESS);
+    if (err)
+        return err;
+    ctx = (sctx_t *) ap_get_module_config(cmd->server->module_config,
+                                          &proxy_hcheck_module);
+
+    name = ap_getword_conf(cmd->temp_pool, &arg);
+    if (!*name) {
+        return apr_pstrcat(cmd->temp_pool, "Missing template name for ",
+                           cmd->cmd->name, NULL);
+    }
+
+    template = (hc_template_t *)apr_array_push(ctx->templates);
+
+    template->name = apr_pstrdup(cmd->pool, name);
+    template->method = template->passes = template->fails = 1;
+    template->interval = apr_time_from_sec(HCHECK_WATHCHDOG_DEFAULT_INTERVAL);
+    template->hurl = NULL;
+    template->hcexpr = NULL;
+    while (*arg) {
+        word = ap_getword_conf(cmd->pool, &arg);
+        val = strchr(word, '=');
+        if (!val) {
+            return "Invalid ProxyHCTemplate parameter. Parameter must be "
+                   "in the form 'key=value'";
+        }
+        else
+            *val++ = '\0';
+        err = set_worker_hc_param(cmd->pool, ctx->s, NULL, word, val, template);
+
+        if (err) {
+            /* get rid of recently pushed (bad) template */
+            apr_array_pop(ctx->templates);
+            return apr_pstrcat(cmd->temp_pool, "ProxyHCTemplate: ", err, " ", word, "=", val, "; ", name, NULL);
+        }
+        /* No error means we have a valid template */
+    }
+    return NULL;
+}
+
+#if HC_USE_THREADS
+static const char *set_hc_tpsize (cmd_parms *cmd, void *dummy, const char *arg)
+{
+    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+    if (err)
+        return err;
+
+    tpsize = atoi(arg);
+    if (tpsize < 0)
+        return "Invalid ProxyHCTPsize parameter. Parameter must be "
+               ">= 0";
+    return NULL;
+}
+#endif
+
+/*
+ * Create a dummy request rec, simply so we can use ap_expr.
+ * Use our short-lived pool for bucket_alloc so that we can simply move
+ * buckets and use them after the backend connection is released.
+ */
+static request_rec *create_request_rec(apr_pool_t *p, server_rec *s,
+                                       proxy_balancer *balancer,
+                                       const char *method,
+                                       const char *protocol)
+{
+    request_rec *r;
+
+    r = apr_pcalloc(p, sizeof(request_rec));
+    r->pool            = p;
+    r->server          = s;
+
+    r->per_dir_config = r->server->lookup_defaults;
+    if (balancer->section_config) {
+        r->per_dir_config = ap_merge_per_dir_configs(r->pool,
+                                                     r->per_dir_config,
+                                                     balancer->section_config);
+    }
+
+    r->proxyreq        = PROXYREQ_RESPONSE;
+
+    r->user            = NULL;
+    r->ap_auth_type    = NULL;
+
+    r->allowed_methods = ap_make_method_list(p, 2);
+
+    r->headers_in      = apr_table_make(r->pool, 1);
+    r->trailers_in     = apr_table_make(r->pool, 1);
+    r->subprocess_env  = apr_table_make(r->pool, 25);
+    r->headers_out     = apr_table_make(r->pool, 12);
+    r->err_headers_out = apr_table_make(r->pool, 5);
+    r->trailers_out    = apr_table_make(r->pool, 1);
+    r->notes           = apr_table_make(r->pool, 5);
+
+    r->request_config  = ap_create_request_config(r->pool);
+    /* Must be set before we run create request hook */
+
+    r->sent_bodyct     = 0;                      /* bytect isn't for body */
+
+    r->read_length     = 0;
+    r->read_body       = REQUEST_NO_BODY;
+
+    r->status          = HTTP_OK;  /* Until further notice */
+    r->the_request     = NULL;
+
+    /* Begin by presuming any module can make its own path_info assumptions,
+     * until some module interjects and changes the value.
+     */
+    r->used_path_info = AP_REQ_DEFAULT_PATH_INFO;
+
+
+    /* Time to populate r with the data we have. */
+    r->method = method;
+    /* Provide quick information about the request method as soon as known */
+    r->method_number = ap_method_number_of(r->method);
+    if (r->method_number == M_OPTIONS
+            || (r->method_number == M_GET && r->method[0] == 'H')) {
+        r->header_only = 1;
+    }
+    else {
+        r->header_only = 0;
+    }
+    r->protocol = "HTTP/1.0";
+    r->proto_num = HTTP_VERSION(1, 0);
+    if ( protocol && (protocol[7] == '1') ) {
+        r->protocol = "HTTP/1.1";
+        r->proto_num = HTTP_VERSION(1, 1);
+    }
+    r->hostname = NULL;
+
+    return r;
+}
+
+static void set_request_connection(request_rec *r, conn_rec *conn)
+{
+    conn->bucket_alloc = apr_bucket_alloc_create(r->pool);
+    r->connection = conn;
+
+    r->kept_body = apr_brigade_create(r->pool, conn->bucket_alloc);
+    r->output_filters = r->proto_output_filters = conn->output_filters;
+    r->input_filters = r->proto_input_filters = conn->input_filters;
+
+    r->useragent_addr = conn->client_addr;
+    r->useragent_ip = conn->client_ip;
+}
+
+static void create_hcheck_req(wctx_t *wctx, proxy_worker *hc,
+                              apr_pool_t *p)
+{
+    char *req = NULL;
+    const char *method = NULL;
+    const char *protocol = NULL;
+
+    /* TODO: Fold into switch/case below? This seems more obvious */
+    if ( (hc->s->method == OPTIONS11) || (hc->s->method == HEAD11) || (hc->s->method == GET11) ) {
+        protocol = "HTTP/1.1";
+    } else {
+        protocol = "HTTP/1.0";
+    }
+    switch (hc->s->method) {
+        case OPTIONS:
+        case OPTIONS11:
+            method = "OPTIONS";
+            req = apr_psprintf(p,
+                               "OPTIONS * %s\r\n"
+                               "Host: %s:%d\r\n"
+                               "\r\n", protocol,
+                               hc->s->hostname_ex, (int)hc->s->port);
+            break;
+
+        case HEAD:
+        case HEAD11:
+            method = "HEAD";
+            /* fallthru */
+        case GET:
+        case GET11:
+            if (!method) { /* did we fall thru? If not, we are GET */
+                method = "GET";
+            }
+            req = apr_psprintf(p,
+                               "%s %s%s%s %s\r\n"
+                               "Host: %s:%d\r\n"
+                               "\r\n",
+                               method,
+                               (wctx->path ? wctx->path : ""),
+                               (wctx->path && *hc->s->hcuri ? "/" : "" ),
+                               (*hc->s->hcuri ? hc->s->hcuri : ""),
+                               protocol,
+                               hc->s->hostname_ex, (int)hc->s->port);
+            break;
+
+        default:
+            break;
+    }
+    wctx->req = req;
+    wctx->method = method;
+    wctx->protocol = protocol;
+}
+
+static proxy_worker *hc_get_hcworker(sctx_t *ctx, proxy_worker *worker,
+                                     apr_pool_t *p)
+{
+    proxy_worker *hc = NULL;
+    apr_port_t port;
+
+    hc = (proxy_worker *)apr_hash_get(ctx->hcworkers, &worker, sizeof worker);
+    if (!hc) {
+        apr_uri_t uri;
+        apr_status_t rv;
+        const char *url = worker->s->name_ex;
+        wctx_t *wctx = apr_pcalloc(ctx->p, sizeof(wctx_t));
+
+        port = (worker->s->port ? worker->s->port
+                                : ap_proxy_port_of_scheme(worker->s->scheme));
+        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ctx->s, APLOGNO(03248)
+                     "Creating hc worker %pp for %s://%s:%d",
+                     worker, worker->s->scheme, worker->s->hostname_ex,
+                     (int)port);
+
+        ap_proxy_define_worker(ctx->p, &hc, NULL, NULL, worker->s->name_ex, 0);
+        apr_snprintf(hc->s->name, sizeof hc->s->name, "%pp", worker);
+        apr_snprintf(hc->s->name_ex, sizeof hc->s->name_ex, "%pp", worker);
+        PROXY_STRNCPY(hc->s->hostname, worker->s->hostname); /* for compatibility */
+        PROXY_STRNCPY(hc->s->hostname_ex, worker->s->hostname_ex);
+        PROXY_STRNCPY(hc->s->scheme,   worker->s->scheme);
+        PROXY_STRNCPY(hc->s->hcuri,    worker->s->hcuri);
+        PROXY_STRNCPY(hc->s->hcexpr,   worker->s->hcexpr);
+        hc->hash.def = hc->s->hash.def = ap_proxy_hashfunc(hc->s->name_ex,
+                                                           PROXY_HASHFUNC_DEFAULT);
+        hc->hash.fnv = hc->s->hash.fnv = ap_proxy_hashfunc(hc->s->name_ex,
+                                                           PROXY_HASHFUNC_FNV);
+        hc->s->port = port;
+        hc->s->conn_timeout_set = worker->s->conn_timeout_set;
+        hc->s->conn_timeout = worker->s->conn_timeout;
+        hc->s->ping_timeout_set = worker->s->ping_timeout_set;
+        hc->s->ping_timeout = worker->s->ping_timeout;
+        hc->s->timeout_set = worker->s->timeout_set;
+        hc->s->timeout = worker->s->timeout;
+        /* Do not disable worker in case of errors */
+        hc->s->status |= PROXY_WORKER_IGNORE_ERRORS;
+        /* Mark as the "generic" worker */
+        hc->s->status |= PROXY_WORKER_GENERIC;
+        ap_proxy_initialize_worker(hc, ctx->s, ctx->p);
+        hc->s->is_address_reusable = worker->s->is_address_reusable;
+        hc->s->disablereuse = worker->s->disablereuse;
+        hc->s->method = worker->s->method;
+        rv = apr_uri_parse(p, url, &uri);
+        if (rv == APR_SUCCESS) {
+            wctx->path = apr_pstrdup(ctx->p, uri.path);
+        }
+        wctx->w = worker;
+        create_hcheck_req(wctx, hc, ctx->p);
+        hc->context = wctx;
+        apr_hash_set(ctx->hcworkers, &worker, sizeof worker, hc);
+    }
+    /* This *could* have changed via the Balancer Manager */
+    /* TODO */
+    if (hc->s->method != worker->s->method) {
+        wctx_t *wctx = hc->context;
+        port = (worker->s->port ? worker->s->port
+                                : ap_proxy_port_of_scheme(worker->s->scheme));
+        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ctx->s, APLOGNO(03311)
+                     "Updating hc worker %pp for %s://%s:%d",
+                     worker, worker->s->scheme, worker->s->hostname_ex,
+                     (int)port);
+        hc->s->method = worker->s->method;
+        create_hcheck_req(wctx, hc, ctx->p);
+    }
+    return hc;
+}
+
+static int hc_determine_connection(sctx_t *ctx, proxy_worker *worker,
+                                   apr_sockaddr_t **addr, apr_pool_t *p)
+{
+    apr_status_t rv = APR_SUCCESS;
+    /*
+     * normally, this is done in ap_proxy_determine_connection().
+     * TODO: Look at using ap_proxy_determine_connection() with a
+     * fake request_rec
+     */
+    if (worker->cp->addr) {
+        *addr = worker->cp->addr;
+    }
+    else {
+        rv = apr_sockaddr_info_get(addr, worker->s->hostname_ex,
+                                   APR_UNSPEC, worker->s->port, 0, p);
+        if (rv != APR_SUCCESS) {
+            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ctx->s, APLOGNO(03249)
+                         "DNS lookup failure for: %s:%d",
+                         worker->s->hostname_ex, (int)worker->s->port);
+        }
+    }
+    return (rv == APR_SUCCESS ? OK : !OK);
+}
+
+static apr_status_t hc_init_worker(sctx_t *ctx, proxy_worker *worker)
+{
+    apr_status_t rv = APR_SUCCESS;
+    /*
+     * Since this is the watchdog, workers never actually handle a
+     * request here, and so the local data isn't initialized (of
+     * course, the shared memory is). So we need to bootstrap
+     * worker->cp. Note, we only need do this once.
+     */
+    if (!worker->cp) {
+        rv = ap_proxy_initialize_worker(worker, ctx->s, ctx->p);
+        if (rv != APR_SUCCESS) {
+            ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ctx->s, APLOGNO(03250) "Cannot init worker");
+            return rv;
+        }
+        if (worker->s->is_address_reusable && !worker->s->disablereuse &&
+                hc_determine_connection(ctx, worker, &worker->cp->addr,
+                                        worker->cp->pool) != OK) {
+            rv = APR_EGENERAL;
+        }
+    }
+    return rv;
+}
+
+static apr_status_t backend_cleanup(const char *proxy_function, proxy_conn_rec *backend,
+                                    server_rec *s, int status)
+{
+    if (backend) {
+        backend->close = 1;
+        ap_proxy_release_connection(proxy_function, backend, s);
+        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(03251)
+                         "Health check %s Status (%d) for %s.",
+                         ap_proxy_show_hcmethod(backend->worker->s->method),
+                         status,
+                         backend->worker->s->name_ex);
+    }
+    if (status != OK) {
+        return APR_EGENERAL;
+    }
+    return APR_SUCCESS;
+}
+
+static int hc_get_backend(const char *proxy_function, proxy_conn_rec **backend,
+                          proxy_worker *hc, sctx_t *ctx, apr_pool_t *ptemp)
+{
+    int status;
+    status = ap_proxy_acquire_connection(proxy_function, backend, hc, ctx->s);
+    if (status == OK) {
+        (*backend)->addr = hc->cp->addr;
+        (*backend)->hostname = hc->s->hostname_ex;
+        if (strcmp(hc->s->scheme, "https") == 0 || strcmp(hc->s->scheme, "wss") == 0 ) {
+            if (!ap_ssl_has_outgoing_handlers()) {
+                ap_log_error(APLOG_MARK, APLOG_WARNING, 0, ctx->s, APLOGNO(03252)
+                              "mod_ssl not configured?");
+                return !OK;
+            }
+            (*backend)->is_ssl = 1;
+        }
+
+    }
+    return hc_determine_connection(ctx, hc, &(*backend)->addr, ptemp);
+}
+
+static apr_status_t hc_check_cping(baton_t *baton, apr_thread_t *thread)
+{
+    int status;
+    sctx_t *ctx = baton->ctx;
+    proxy_worker *hc = baton->hc;
+    proxy_conn_rec *backend = NULL;
+    apr_pool_t *ptemp = baton->ptemp;
+    request_rec *r;
+    apr_interval_time_t timeout;
+
+    if (!ajp_handle_cping_cpong) {
+        return APR_ENOTIMPL;
+    }
+
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, baton->ctx->s, "HCCPING starting");
+    if ((status = hc_get_backend("HCCPING", &backend, hc, ctx, baton->ptemp)) != OK) {
+        return backend_cleanup("HCCPING", backend, ctx->s, status);
+    }
+    if ((status = ap_proxy_connect_backend("HCCPING", backend, hc, ctx->s)) != OK) {
+        return backend_cleanup("HCCPING", backend, ctx->s, status);
+    }
+    r = create_request_rec(ptemp, ctx->s, baton->balancer, "CPING", NULL);
+    if ((status = ap_proxy_connection_create_ex("HCCPING", backend, r)) != OK) {
+        return backend_cleanup("HCCPING", backend, ctx->s, status);
+    }
+    set_request_connection(r, backend->connection);
+    backend->connection->current_thread = thread;
+
+    if (hc->s->ping_timeout_set) {
+        timeout = hc->s->ping_timeout;
+    } else if ( hc->s->conn_timeout_set) {
+        timeout = hc->s->conn_timeout;
+    } else if ( hc->s->timeout_set) {
+        timeout = hc->s->timeout;
+    } else {
+        /* default to socket timeout */
+        apr_socket_timeout_get(backend->sock, &timeout); 
+    }
+    status = ajp_handle_cping_cpong(backend->sock, r, timeout);
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, baton->ctx->s, "HCCPING done %d", status);
+    return backend_cleanup("HCCPING", backend, ctx->s, status);
+}
+
+static apr_status_t hc_check_tcp(baton_t *baton)
+{
+    int status;
+    sctx_t *ctx = baton->ctx;
+    proxy_worker *hc = baton->hc;
+    proxy_conn_rec *backend = NULL;
+
+    status = hc_get_backend("HCTCP", &backend, hc, ctx, baton->ptemp);
+    if (status == OK) {
+        status = ap_proxy_connect_backend("HCTCP", backend, hc, ctx->s);
+        /* does an unconditional ap_proxy_is_socket_connected() */
+    }
+    return backend_cleanup("HCTCP", backend, ctx->s, status);
+}
+
+static int hc_send(request_rec *r, const char *out, apr_bucket_brigade *bb)
+{
+    apr_status_t rv;
+    conn_rec *c = r->connection;
+    apr_bucket_alloc_t *ba = c->bucket_alloc;
+    ap_log_error(APLOG_MARK, APLOG_TRACE7, 0, r->server, "%s", out);
+    APR_BRIGADE_INSERT_TAIL(bb, apr_bucket_pool_create(out, strlen(out),
+                                                       r->pool, ba));
+    APR_BRIGADE_INSERT_TAIL(bb, apr_bucket_flush_create(ba));
+    rv = ap_pass_brigade(c->output_filters, bb);
+    apr_brigade_cleanup(bb);
+    return (rv) ? !OK : OK;
+}
+
+static int hc_read_headers(request_rec *r)
+{
+    char buffer[HUGE_STRING_LEN];
+    int len;
+    const char *ct;
+
+    len = ap_getline(buffer, sizeof(buffer), r, 1);
+    if (len <= 0) {
+        return !OK;
+    }
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server, APLOGNO(03254)
+                 "%.*s", len, buffer);
+    /* for the below, see ap_proxy_http_process_response() */
+    if (apr_date_checkmask(buffer, "HTTP/#.# ###*")) {
+        int major;
+        char keepchar;
+        int proxy_status = OK;
+        const char *proxy_status_line = NULL;
+
+        major = buffer[5] - '0';
+        if ((major != 1) || (len >= sizeof(buffer)-1)) {
+            return !OK;
+        }
+
+        keepchar = buffer[12];
+        buffer[12] = '\0';
+        proxy_status = atoi(&buffer[9]);
+        if (keepchar != '\0') {
+            buffer[12] = keepchar;
+        } else {
+            buffer[12] = ' ';
+            buffer[13] = '\0';
+        }
+        proxy_status_line = apr_pstrdup(r->pool, &buffer[9]);
+        r->status = proxy_status;
+        r->status_line = proxy_status_line;
+    } else {
+        return !OK;
+    }
+
+    /* OK, 1st line is OK... scarf in the headers */
+    while ((len = ap_getline(buffer, sizeof(buffer), r, 1)) > 0) {
+        char *value, *end;
+        ap_log_error(APLOG_MARK, APLOG_TRACE7, 0, r->server, "%.*s",
+                     len, buffer);
+        if (!(value = strchr(buffer, ':'))) {
+            return !OK;
+        }
+        *value = '\0';
+        ++value;
+        while (apr_isspace(*value))
+            ++value;            /* Skip to start of value   */
+        for (end = &value[strlen(value)-1]; end > value && apr_isspace(*end); --end)
+            *end = '\0';
+        apr_table_add(r->headers_out, buffer, value);
+    }
+
+    /* Set the Content-Type for the request if set */
+    if ((ct = apr_table_get(r->headers_out, "Content-Type")) != NULL)
+        ap_set_content_type(r, ct);
+
+    return OK;
+}
+
+static int hc_read_body(request_rec *r, apr_bucket_brigade *bb)
+{
+    apr_status_t rv = APR_SUCCESS;
+    int seen_eos = 0;
+
+    do {
+        apr_size_t len = HUGE_STRING_LEN;
+
+        apr_brigade_cleanup(bb);
+        rv = ap_get_brigade(r->proto_input_filters, bb, AP_MODE_READBYTES,
+                            APR_BLOCK_READ, len);
+
+        if (rv != APR_SUCCESS) {
+            if (APR_STATUS_IS_EOF(rv)) {
+                rv = APR_SUCCESS;
+                break;
+            }
+            ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, r->server, APLOGNO(03300)
+                          "Error reading response body");
+            break;
+        }
+
+        while (!APR_BRIGADE_EMPTY(bb)) {
+            apr_bucket *bucket = APR_BRIGADE_FIRST(bb);
+            if (APR_BUCKET_IS_EOS(bucket)) {
+                seen_eos = 1;
+                break;
+            }
+            if (APR_BUCKET_IS_FLUSH(bucket)) {
+                apr_bucket_delete(bucket);
+                continue;
+            }
+            APR_BUCKET_REMOVE(bucket);
+            APR_BRIGADE_INSERT_TAIL(r->kept_body, bucket);
+        }
+    }
+    while (!seen_eos);
+    apr_brigade_cleanup(bb);
+    return (rv == APR_SUCCESS ? OK : !OK);
+}
+
+/*
+ * Send the HTTP OPTIONS, HEAD or GET request to the backend
+ * server associated w/ worker. If we have Conditions,
+ * then apply those to the resulting response, otherwise
+ * any status code 2xx or 3xx is considered "passing"
+ */
+static apr_status_t hc_check_http(baton_t *baton, apr_thread_t *thread)
+{
+    int status;
+    proxy_conn_rec *backend = NULL;
+    sctx_t *ctx = baton->ctx;
+    proxy_worker *hc = baton->hc;
+    proxy_worker *worker = baton->worker;
+    apr_pool_t *ptemp = baton->ptemp;
+    request_rec *r;
+    wctx_t *wctx;
+    hc_condition_t *cond;
+    apr_bucket_brigade *bb;
+
+    wctx = (wctx_t *)hc->context;
+    if (!wctx->req || !wctx->method) {
+        return APR_ENOTIMPL;
+    }
+
+    if ((status = hc_get_backend("HCOH", &backend, hc, ctx, ptemp)) != OK) {
+        return backend_cleanup("HCOH", backend, ctx->s, status);
+    }
+    if ((status = ap_proxy_connect_backend("HCOH", backend, hc, ctx->s)) != OK) {
+        return backend_cleanup("HCOH", backend, ctx->s, status);
+    }
+
+    r = create_request_rec(ptemp, ctx->s, baton->balancer, wctx->method, wctx->protocol);
+    if ((status = ap_proxy_connection_create_ex("HCOH", backend, r)) != OK) {
+        return backend_cleanup("HCOH", backend, ctx->s, status);
+    }
+    set_request_connection(r, backend->connection);
+    backend->connection->current_thread = thread;
+
+    bb = apr_brigade_create(r->pool, r->connection->bucket_alloc);
+
+    if ((status = hc_send(r, wctx->req, bb)) != OK) {
+        return backend_cleanup("HCOH", backend, ctx->s, status);
+    }
+    if ((status = hc_read_headers(r)) != OK) {
+        return backend_cleanup("HCOH", backend, ctx->s, status);
+    }
+    if (!r->header_only) {
+        apr_table_t *saved_headers_in = r->headers_in;
+        r->headers_in = apr_table_copy(r->pool, r->headers_out);
+        ap_proxy_pre_http_request(backend->connection, r);
+        status = hc_read_body(r, bb);
+        r->headers_in = saved_headers_in;
+        if (status != OK) {
+            return backend_cleanup("HCOH", backend, ctx->s, status);
+        }
+        r->trailers_out = apr_table_copy(r->pool, r->trailers_in);
+    }
+
+    if (*worker->s->hcexpr &&
+            (cond = (hc_condition_t *)apr_table_get(ctx->conditions, worker->s->hcexpr)) != NULL) {
+        const char *err;
+        int ok = ap_expr_exec(r, cond->pexpr, &err);
+        if (ok > 0) {
+            ap_log_error(APLOG_MARK, APLOG_TRACE2, 0, ctx->s,
+                         "Condition %s for %s (%s): passed", worker->s->hcexpr,
+                         hc->s->name_ex, worker->s->name_ex);
+        } else if (ok < 0 || err) {
+            ap_log_error(APLOG_MARK, APLOG_INFO, 0, ctx->s, APLOGNO(03301)
+                         "Error on checking condition %s for %s (%s): %s", worker->s->hcexpr,
+                         hc->s->name_ex, worker->s->name_ex, err);
+            status = !OK;
+        } else {
+            ap_log_error(APLOG_MARK, APLOG_TRACE2, 0, ctx->s,
+                         "Condition %s for %s (%s) : failed", worker->s->hcexpr,
+                         hc->s->name_ex, worker->s->name_ex);
+            status = !OK;
+        }
+    } else if (r->status < 200 || r->status > 399) {
+        ap_log_error(APLOG_MARK, APLOG_TRACE2, 0, ctx->s,
+                     "Response status %i for %s (%s): failed", r->status,
+                     hc->s->name_ex, worker->s->name_ex);
+        status = !OK;
+    }
+    return backend_cleanup("HCOH", backend, ctx->s, status);
+}
+
+static void * APR_THREAD_FUNC hc_check(apr_thread_t *thread, void *b)
+{
+    baton_t *baton = (baton_t *)b;
+    server_rec *s = baton->ctx->s;
+    proxy_worker *worker = baton->worker;
+    proxy_worker *hc = baton->hc;
+    apr_time_t now;
+    apr_status_t rv;
+
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(03256)
+                 "%sHealth checking %s", (thread ? "Threaded " : ""),
+                 worker->s->name_ex);
+
+    if (hc->s->method == TCP) {
+        rv = hc_check_tcp(baton);
+    }
+    else if (hc->s->method == CPING) {
+        rv = hc_check_cping(baton, thread);
+    }
+    else {
+        rv = hc_check_http(baton, thread);
+    }
+
+    now = apr_time_now();
+    if (rv == APR_ENOTIMPL) {
+        ap_log_error(APLOG_MARK, APLOG_ERR, 0, s, APLOGNO(03257)
+                         "Somehow tried to use unimplemented hcheck method: %d",
+                         (int)hc->s->method);
+    }
+    /* what state are we in ? */
+    else if (PROXY_WORKER_IS_HCFAILED(worker) || PROXY_WORKER_IS_ERROR(worker)) {
+        if (rv == APR_SUCCESS) {
+            worker->s->pcount += 1;
+            if (worker->s->pcount >= worker->s->passes) {
+                ap_proxy_set_wstatus(PROXY_WORKER_HC_FAIL_FLAG, 0, worker);
+                ap_proxy_set_wstatus(PROXY_WORKER_IN_ERROR_FLAG, 0, worker);
+                worker->s->pcount = 0;
+                ap_log_error(APLOG_MARK, APLOG_INFO, 0, s, APLOGNO(03302)
+                             "%sHealth check ENABLING %s", (thread ? "Threaded " : ""),
+                             worker->s->name_ex);
+
+            }
+        }
+    }
+    else {
+        if (rv != APR_SUCCESS) {
+            worker->s->error_time = now;
+            worker->s->fcount += 1;
+            if (worker->s->fcount >= worker->s->fails) {
+                ap_proxy_set_wstatus(PROXY_WORKER_HC_FAIL_FLAG, 1, worker);
+                worker->s->fcount = 0;
+                ap_log_error(APLOG_MARK, APLOG_INFO, 0, s, APLOGNO(03303)
+                             "%sHealth check DISABLING %s", (thread ? "Threaded " : ""),
+                             worker->s->name_ex);
+            }
+        }
+    }
+    if (baton->now) {
+        *baton->now = now;
+    }
+    apr_pool_destroy(baton->ptemp);
+    worker->s->updated = now;
+
+    return NULL;
+}
+
+static apr_status_t hc_watchdog_callback(int state, void *data,
+                                         apr_pool_t *pool)
+{
+    apr_status_t rv = APR_SUCCESS;
+    proxy_balancer *balancer;
+    sctx_t *ctx = (sctx_t *)data;
+    server_rec *s = ctx->s;
+    proxy_server_conf *conf;
+
+    switch (state) {
+        case AP_WATCHDOG_STATE_STARTING:
+            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(03258)
+                         "%s watchdog started.",
+                         HCHECK_WATHCHDOG_NAME);
+#if HC_USE_THREADS
+            if (tpsize && hctp == NULL) {
+                rv =  apr_thread_pool_create(&hctp, tpsize,
+                                             tpsize, ctx->p);
+                if (rv != APR_SUCCESS) {
+                    ap_log_error(APLOG_MARK, APLOG_INFO, rv, s, APLOGNO(03312)
+                                 "apr_thread_pool_create() with %d threads failed",
+                                 tpsize);
+                    /* we can continue on without the threadpools */
+                    hctp = NULL;
+                } else {
+                    ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, s, APLOGNO(03313)
+                                 "apr_thread_pool_create() with %d threads succeeded",
+                                 tpsize);
+                }
+            } else {
+                ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, s, APLOGNO(03314)
+                             "Skipping apr_thread_pool_create()");
+                hctp = NULL;
+            }
+#endif
+            break;
+
+        case AP_WATCHDOG_STATE_RUNNING:
+            /* loop thru all workers */
+            if (s) {
+                int i;
+                conf = (proxy_server_conf *) ap_get_module_config(s->module_config, &proxy_module);
+                balancer = (proxy_balancer *)conf->balancers->elts;
+                ctx->s = s;
+                for (i = 0; i < conf->balancers->nelts; i++, balancer++) {
+                    int n;
+                    apr_time_t now;
+                    proxy_worker **workers;
+                    proxy_worker *worker;
+                    /* Have any new balancers or workers been added dynamically? */
+                    ap_proxy_sync_balancer(balancer, s, conf);
+                    workers = (proxy_worker **)balancer->workers->elts;
+                    now = apr_time_now();
+                    for (n = 0; n < balancer->workers->nelts; n++) {
+                        worker = *workers;
+                        if (!PROXY_WORKER_IS(worker, PROXY_WORKER_STOPPED) &&
+                            (worker->s->method != NONE) &&
+                            (worker->s->updated != 0) &&
+                            (now > worker->s->updated + worker->s->interval)) {
+                            baton_t *baton;
+                            apr_pool_t *ptemp;
+
+                            ap_log_error(APLOG_MARK, APLOG_TRACE3, 0, s,
+                                         "Checking %s worker: %s  [%d] (%pp)", balancer->s->name,
+                                         worker->s->name_ex, worker->s->method, worker);
+
+                            if ((rv = hc_init_worker(ctx, worker)) != APR_SUCCESS) {
+                                worker->s->updated = now;
+                                return rv;
+                            }
+                            worker->s->updated = 0;
+
+                            /* This pool has the lifetime of the check */
+                            apr_pool_create(&ptemp, ctx->p);
+                            apr_pool_tag(ptemp, "hc_request");
+                            baton = apr_pcalloc(ptemp, sizeof(baton_t));
+                            baton->ctx = ctx;
+                            baton->balancer = balancer;
+                            baton->worker = worker;
+                            baton->ptemp = ptemp;
+                            baton->hc = hc_get_hcworker(ctx, worker, ptemp);
+#if HC_USE_THREADS
+                            if (hctp) {
+                                apr_thread_pool_push(hctp, hc_check, (void *)baton,
+                                                     APR_THREAD_TASK_PRIORITY_NORMAL,
+                                                     NULL);
+                            }
+                            else
+#endif
+                            {
+                                baton->now = &now;
+                                hc_check(NULL, baton);
+                            }
+                        }
+                        workers++;
+                    }
+                }
+            }
+            break;
+
+        case AP_WATCHDOG_STATE_STOPPING:
+            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(03261)
+                         "stopping %s watchdog.",
+                         HCHECK_WATHCHDOG_NAME);
+#if HC_USE_THREADS
+            if (hctp) {
+                rv =  apr_thread_pool_destroy(hctp);
+                if (rv != APR_SUCCESS) {
+                    ap_log_error(APLOG_MARK, APLOG_INFO, rv, s, APLOGNO(03315)
+                                 "apr_thread_pool_destroy() failed");
+                }
+                hctp = NULL;
+            }
+#endif
+            break;
+    }
+    return rv;
+}
+static int hc_pre_config(apr_pool_t *pconf, apr_pool_t *plog,
+                         apr_pool_t *ptemp)
+{
+#if HC_USE_THREADS
+    hctp = NULL;
+    tpsize = HC_THREADPOOL_SIZE;
+#endif
+
+    ajp_handle_cping_cpong = APR_RETRIEVE_OPTIONAL_FN(ajp_handle_cping_cpong);
+    if (ajp_handle_cping_cpong) {
+       proxy_hcmethods_t *method = proxy_hcmethods;
+       for (; method->name; method++) {
+           if (method->method == CPING) {
+               method->implemented = 1;
+               break;
+           }
+       }
+    }
+
+    return OK;
+}
+static int hc_post_config(apr_pool_t *p, apr_pool_t *plog,
+                       apr_pool_t *ptemp, server_rec *main_s)
+{
+    apr_status_t rv;
+    server_rec *s = main_s;
+
+    APR_OPTIONAL_FN_TYPE(ap_watchdog_get_instance) *hc_watchdog_get_instance;
+    APR_OPTIONAL_FN_TYPE(ap_watchdog_register_callback) *hc_watchdog_register_callback;
+
+    if (ap_state_query(AP_SQ_MAIN_STATE) == AP_SQ_MS_CREATE_PRE_CONFIG) {
+        return OK;
+    }
+    hc_watchdog_get_instance = APR_RETRIEVE_OPTIONAL_FN(ap_watchdog_get_instance);
+    hc_watchdog_register_callback = APR_RETRIEVE_OPTIONAL_FN(ap_watchdog_register_callback);
+    if (!hc_watchdog_get_instance || !hc_watchdog_register_callback) {
+        ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s, APLOGNO(03262)
+                     "mod_watchdog is required");
+        return !OK;
+    }
+    rv = hc_watchdog_get_instance(&watchdog,
+                                  HCHECK_WATHCHDOG_NAME,
+                                  0, 1, p);
+    if (rv) {
+        ap_log_error(APLOG_MARK, APLOG_CRIT, rv, s, APLOGNO(03263)
+                     "Failed to create watchdog instance (%s)",
+                     HCHECK_WATHCHDOG_NAME);
+        return !OK;
+    }
+    while (s) {
+        sctx_t *ctx = ap_get_module_config(s->module_config,
+                                           &proxy_hcheck_module);
+
+        if (s != ctx->s) {
+            ap_log_error(APLOG_MARK, APLOG_TRACE4, 0, s, APLOGNO(10019)
+                         "Missing unique per-server context: %s (%pp:%pp) (no hchecks)",
+                         s->server_hostname, s, ctx->s);
+            s = s->next;
+            continue;
+        }
+        rv = hc_watchdog_register_callback(watchdog,
+                AP_WD_TM_SLICE,
+                ctx,
+                hc_watchdog_callback);
+        if (rv) {
+            ap_log_error(APLOG_MARK, APLOG_CRIT, rv, s, APLOGNO(03264)
+                         "Failed to register watchdog callback (%s)",
+                         HCHECK_WATHCHDOG_NAME);
+            return !OK;
+        }
+        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(03265)
+                     "watchdog callback registered (%s for %s)", HCHECK_WATHCHDOG_NAME, s->server_hostname);
+        s = s->next;
+    }
+
+    return OK;
+}
+
+static void hc_show_exprs(request_rec *r)
+{
+    const apr_table_entry_t *elts;
+    const apr_array_header_t *hdr;
+    int i;
+    sctx_t *ctx = (sctx_t *) ap_get_module_config(r->server->module_config,
+                                                  &proxy_hcheck_module);
+    if (!ctx)
+        return;
+    if (apr_is_empty_table(ctx->conditions))
+        return;
+
+    ap_rputs("\n\n<table>"
+             "<tr><th colspan='2'>Health check cond. expressions:</th></tr>\n"
+             "<tr><th>Expr name</th><th>Expression</th></tr>\n", r);
+
+    hdr = apr_table_elts(ctx->conditions);
+    elts = (const apr_table_entry_t *) hdr->elts;
+    for (i = 0; i < hdr->nelts; ++i) {
+        hc_condition_t *cond;
+        if (!elts[i].key) {
+            continue;
+        }
+        cond = (hc_condition_t *)elts[i].val;
+        ap_rprintf(r, "<tr><td>%s</td><td>%s</td></tr>\n",
+                   ap_escape_html(r->pool, elts[i].key),
+                   ap_escape_html(r->pool, cond->expr));
+    }
+    ap_rputs("</table><hr/>\n", r);
+}
+
+static void hc_select_exprs(request_rec *r, const char *expr)
+{
+    const apr_table_entry_t *elts;
+    const apr_array_header_t *hdr;
+    int i;
+    sctx_t *ctx = (sctx_t *) ap_get_module_config(r->server->module_config,
+                                                  &proxy_hcheck_module);
+    if (!ctx)
+        return;
+    if (apr_is_empty_table(ctx->conditions))
+        return;
+
+    hdr = apr_table_elts(ctx->conditions);
+    elts = (const apr_table_entry_t *) hdr->elts;
+    for (i = 0; i < hdr->nelts; ++i) {
+        if (!elts[i].key) {
+            continue;
+        }
+        ap_rprintf(r, "<option value='%s' %s >%s</option>\n",
+                   ap_escape_html(r->pool, elts[i].key),
+                   (!strcmp(elts[i].key, expr)) ? "selected" : "",
+                           ap_escape_html(r->pool, elts[i].key));
+    }
+}
+
+static int hc_valid_expr(request_rec *r, const char *expr)
+{
+    const apr_table_entry_t *elts;
+    const apr_array_header_t *hdr;
+    int i;
+    sctx_t *ctx = (sctx_t *) ap_get_module_config(r->server->module_config,
+                                                  &proxy_hcheck_module);
+    if (!ctx)
+        return 0;
+    if (apr_is_empty_table(ctx->conditions))
+        return 0;
+
+    hdr = apr_table_elts(ctx->conditions);
+    elts = (const apr_table_entry_t *) hdr->elts;
+    for (i = 0; i < hdr->nelts; ++i) {
+        if (!elts[i].key) {
+            continue;
+        }
+        if (!strcmp(elts[i].key, expr))
+            return 1;
+    }
+    return 0;
+}
+
+static const char *hc_get_body(request_rec *r)
+{
+    apr_off_t length;
+    apr_size_t len;
+    apr_status_t rv;
+    char *buf;
+
+    if (!r || !r->kept_body)
+        return "";
+
+    rv = apr_brigade_length(r->kept_body, 1, &length);
+    len = (apr_size_t)length;
+    if (rv != APR_SUCCESS || len == 0)
+        return "";
+
+    buf = apr_palloc(r->pool, len + 1);
+    rv = apr_brigade_flatten(r->kept_body, buf, &len);
+    if (rv != APR_SUCCESS)
+        return "";
+    buf[len] = '\0'; /* ensure */
+    return (const char*)buf;
+}
+
+static const char *hc_expr_var_fn(ap_expr_eval_ctx_t *ctx, const void *data)
+{
+    char *var = (char *)data;
+
+    if (var && *var && ctx->r && ap_cstr_casecmp(var, "BODY") == 0) {
+        return hc_get_body(ctx->r);
+    }
+    return NULL;
+}
+
+static const char *hc_expr_func_fn(ap_expr_eval_ctx_t *ctx, const void *data,
+                                const char *arg)
+{
+    char *var = (char *)arg;
+
+    if (var && *var && ctx->r && ap_cstr_casecmp(var, "BODY") == 0) {
+        return hc_get_body(ctx->r);
+    }
+    return NULL;
+}
+
+static int hc_expr_lookup(ap_expr_lookup_parms *parms)
+{
+    switch (parms->type) {
+    case AP_EXPR_FUNC_VAR:
+        /* for now, we just handle everything that starts with HC_.
+         */
+        if (strncasecmp(parms->name, "HC_", 3) == 0) {
+            *parms->func = hc_expr_var_fn;
+            *parms->data = parms->name + 3;
+            return OK;
+        }
+        break;
+    case AP_EXPR_FUNC_STRING:
+        /* Function HC() is implemented by us.
+         */
+        if (strcasecmp(parms->name, "HC") == 0) {
+            *parms->func = hc_expr_func_fn;
+            *parms->data = parms->arg;
+            return OK;
+        }
+        break;
+    }
+    return DECLINED;
+}
+
+static const command_rec command_table[] = {
+    AP_INIT_RAW_ARGS("ProxyHCTemplate", set_hc_template, NULL, OR_FILEINFO,
+                     "Health check template"),
+    AP_INIT_RAW_ARGS("ProxyHCExpr", set_hc_condition, NULL, OR_FILEINFO,
+                     "Define a health check condition ruleset expression"),
+#if HC_USE_THREADS
+    AP_INIT_TAKE1("ProxyHCTPsize", set_hc_tpsize, NULL, RSRC_CONF,
+                     "Set size of health check thread pool"),
+#endif
+    { NULL }
+};
+
+static void hc_register_hooks(apr_pool_t *p)
+{
+    static const char *const aszPre[] = { "mod_proxy_balancer.c", "mod_proxy.c", NULL};
+    static const char *const aszSucc[] = { "mod_watchdog.c", NULL};
+    APR_REGISTER_OPTIONAL_FN(set_worker_hc_param);
+    APR_REGISTER_OPTIONAL_FN(hc_show_exprs);
+    APR_REGISTER_OPTIONAL_FN(hc_select_exprs);
+    APR_REGISTER_OPTIONAL_FN(hc_valid_expr);
+    ap_hook_pre_config(hc_pre_config, NULL, NULL, APR_HOOK_MIDDLE);
+    ap_hook_post_config(hc_post_config, aszPre, aszSucc, APR_HOOK_LAST);
+    ap_hook_expr_lookup(hc_expr_lookup, NULL, NULL, APR_HOOK_MIDDLE);
+}
+
+/* the main config structure */
+
+AP_DECLARE_MODULE(proxy_hcheck) =
+{
+    STANDARD20_MODULE_STUFF,
+    NULL,              /* create per-dir config structures */
+    NULL,              /* merge  per-dir config structures */
+    hc_create_config,  /* create per-server config structures */
+    NULL,              /* merge  per-server config structures */
+    command_table,     /* table of config file commands */
+    hc_register_hooks  /* register hooks */
+};