Support export via TLS (fix #12).

src/batch_exporter.hpp

@@ -111,10 +111,10 @@ public:
         int attrSize{0};
     };
 
-    BatchExporter(StrView target,
+    BatchExporter(StrView target, bool ssl, const std::string& trustedCert,
             size_t batchSize, size_t batchCount,
             const std::map<StrView, StrView>& resourceAttrs) :
-        batchSize(batchSize), client(std::string(target))
+        batchSize(batchSize), client(std::string(target), ssl, trustedCert)
     {
         free.reserve(batchCount);
         while (batchCount-- > 0) {

src/http_module.cpp

@@ -6,6 +6,8 @@
 #include "trace_context.hpp"
 #include "batch_exporter.hpp"
 
+#include <fstream>
+
 extern ngx_module_t gHttpModule;
 
 namespace {
@@ -26,6 +28,8 @@ struct MainConfBase {
 
 struct MainConf : MainConfBase {
     std::map<StrView, StrView> resourceAttrs;
+    bool ssl;
+    std::string trustedCert;
 };
 
 struct SpanAttr {
@@ -44,6 +48,7 @@ struct LocationConf {
 char* setExporter(ngx_conf_t* cf, ngx_command_t* cmd, void* conf);
 char* addResourceAttr(ngx_conf_t* cf, ngx_command_t* cmd, void* conf);
 char* addSpanAttr(ngx_conf_t* cf, ngx_command_t* cmd, void* conf);
+char* setTrustedCertificate(ngx_conf_t* cf, ngx_command_t* cmd, void* conf);
 
 namespace Propagation {
 
@@ -111,6 +116,10 @@ ngx_command_t gExporterCommands[] = {
       0,
       offsetof(MainConfBase, endpoint) },
 
+    { ngx_string("trusted_certificate"),
+      NGX_CONF_TAKE1,
+      setTrustedCertificate },
+
     { ngx_string("interval"),
       NGX_CONF_TAKE1,
       ngx_conf_set_msec_slot,
@@ -569,6 +578,8 @@ ngx_int_t initWorkerProcess(ngx_cycle_t* cycle)
     try {
         gExporter.reset(new BatchExporter(
             toStrView(mcf->endpoint),
+            mcf->ssl,
+            mcf->trustedCert,
             mcf->batchSize,
             mcf->batchCount,
             mcf->resourceAttrs));
@@ -671,9 +682,7 @@ char* setExporter(ngx_conf_t* cf, ngx_command_t* cmd, void* conf)
     }
 
     if (iremovePrefix(&mcf->endpoint, "https://")) {
-        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+        mcf->ssl = true;
-            "\"otel_exporter\" doesn't support \"https\" endpoints");
-        return (char*)NGX_CONF_ERROR;
     } else {
         iremovePrefix(&mcf->endpoint, "http://");
     }
@@ -702,6 +711,36 @@ char* addResourceAttr(ngx_conf_t* cf, ngx_command_t* cmd, void* conf)
     return NGX_CONF_OK;
 }
 
+char* setTrustedCertificate(ngx_conf_t* cf, ngx_command_t* cmd, void* conf) {
+    auto path = ((ngx_str_t*)cf->args->elts)[1];
+    auto mcf = getMainConf(cf);
+
+    if (ngx_get_full_name(cf->pool, &cf->cycle->conf_prefix, &path) != NGX_OK) {
+        return (char*)NGX_CONF_ERROR;
+    }
+
+    try {
+        std::ifstream file{(const char*)path.data, std::ios::binary};
+        if (!file.is_open()) {
+            ngx_conf_log_error(NGX_LOG_EMERG, cf, ngx_errno,
+                "failed to open \"%V\"", &path);
+            return (char*)NGX_CONF_ERROR;
+        }
+        file.exceptions(std::ios::failbit | std::ios::badbit);
+        file.seekg(0, std::ios::end);
+        size_t size = file.tellg();
+        mcf->trustedCert.resize(size);
+        file.seekg(0);
+        file.read(&mcf->trustedCert[0], mcf->trustedCert.size());
+    } catch (const std::exception& e) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+            "failed to read \"%V\": %s", &path, e.what());
+        return (char*)NGX_CONF_ERROR;
+    }
+
+    return NGX_CONF_OK;
+}
+
 void* createMainConf(ngx_conf_t* cf)
 {
     auto cln = ngx_pool_cleanup_add(cf->pool, sizeof(MainConf));

src/trace_service_client.hpp

@@ -17,10 +17,18 @@ public:
     typedef std::function<void (Request, Response, grpc::Status)>
         ResponseCb;
 
-    TraceServiceClient(const std::string& target)
+    TraceServiceClient(const std::string& target, bool ssl,
+        const std::string& trustedCert)
     {
-        auto channel = grpc::CreateChannel(
+        std::shared_ptr<grpc::ChannelCredentials> creds;
-            target, grpc::InsecureChannelCredentials());
+        if (ssl) {
+            grpc::SslCredentialsOptions options;
+            options.pem_root_certs = trustedCert;
+            creds = grpc::SslCredentials(options);
+        } else {
+            creds = grpc::InsecureChannelCredentials();
+        }
+        auto channel = grpc::CreateChannel(target, creds);
         channel->GetState(true); // trigger 'connecting' state
 
         stub = TraceService::NewStub(channel);