Russia–Sri Lanka relations
The Soviet Union established diplomatic relations with Sri Lanka on December 3–6, 1956. In 1958, the USSR and Sri Lanka signed an agreement on economic and technical cooperation. In 1967, they built a steel mill (production capacity - 50,000 tons of stock per year), a tire plant, and a construction materials plant near Colombo all with the assistance of the Soviet Union.
Russian Federation relations
In the UN, Russia has supported Sri Lanka in nearly every resolution brought forward against them. The most notable one was during the final stages of Sri Lanka's civil war in 2009 when European nations along with Canada and Mexico brought a ceasefire bill against the Sri Lanka Army. However, China and Russia vetoed that bill. Later on, another war crime bill that was tabled by Western nations against the Government of Sri Lanka was once again vetoed by Russia and China, along with several other nations.
Sri Lanka reacted in favor of Russia during the Ukrainian crisis,and acknowledged the concerns of Russia as justifiable. 
Russia helped Sri Lanka to obtain Russian based weapons from several countries throughout the past 30 years. Examples of this would be Mikoyan-Gurevich MiG-27, Mil Mi-17 used by Sri Lanka Air Force and T-54/55 battle tanks, BTR-80 APC used by Sri Lanka Army.
Sri Lanka and Russia have recently ramped up cooperation on expanding the tea trade between the two nations. Currently, approximately 17 percent of Sri Lanka's tea exports go to Russia. Sri Lankan teas account for 30% of Russia's tea market. In 2016, there were 58,176 Russian tourist arrived in Sri lanka. This number is gradually increasing in recent years.
In December, 2017 Russia imposed a temporary restriction on the imports of agriculture products from Sri Lanka including Ceylon tea after an insect called the Khapra beetle was found in a consignment of tea. Later, however, it was revealed that the beetle is neither native to, nor lives in, Sri Lanka. Russia accounts for nearly 19 percent of Sri Lanka’s $ 1.27 billion tea exports. After discussion with official delegation from the Sri Lanka Tea Board, Russia agreed to lift the restrictions from Dec 30. Sri Lanka also lifted a ban on asbestos, mainly imported from Russia. It was suspected Russia was not happy with the pro-Western policy of the UNP led Sri Lankan Government. 
- Russia pledges support to Lanka in its crackdown on LTTE Zee News - May 07, 2009
- “While acknowledging the justifiable concerns of the Russian Federation, Sri Lanka also welcomes attempts at de-escalating the tension. Sri Lanka is confident that the parties concerned would be able to resolve the issues arising out of the recent developments, through a legitimate democratic process, enabling harmonious co-existence of the people of Ukraine.” - See more at: http://www.nation.lk/edition/breaking-news/item/26839-ukraine-crisis-lanka-regrets-presidents-unconstitutional-removal.html#sthash.888W7iUA.dpuf
- "Cabinet approves purchase of Rs.24 billion Russian frigate on credit line: Sunday Times 01 Oct 2017".
- Sri Lanka targets Russia with specialty teas Lanka Business Online - December 19, 2011.
- TOURIST ARRIVALS BY COUNTRY OF RESIDENCE 2016
- (in English) Sri Lanka Renews 51 Year Old Diplomatic Relationship with Russia
- (in Russian) Documents on the Russia – Sri Lanka relationship at the Russian Ministry of Foreign Affairs
- Sri Lanka president met his Russian counterpart Dimitry Medvedev and Chinese President Hu Jintao
- Sri Lanka – A Rajapaksa Factor
- Sri Lanka President warmly welcomed in Russia
- Rajapaksa visits Russia to bolster ties
- Russian envoy calls for stronger SL-Russia ties